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BCMSN Practical Lab Initial Config

Published

on June 9, 2008

in BCMSN, Certification and Cisco Systems

. 0 Comments

The Topology

The above topology shows (from the top) a Distribution and Access switched network design with redundant links between Distribution switches and Distribution and Access Layers. Finally there are two attached end-devices (workstations).

The network is going to use the 192.168.1.0 network using the /24 (255.255.255.0) subnet thus allowing for 254 hosts on the network.

Lets say that the DSW switches are MLS switches for argument sake (I know the diagram doesn’t show it).

If you look at the colour key at the bottom you will find that each link colour combination represents a fastethernet port in this case. It’s a fairly simple Lab so its easy to have each link connected on Access Switch fe0/1 and then Distribution Switch fe0/1 on the other end.

I didn’t want to make much work for myself connecting things weird but you can do that by all means. All that means is that you really have to pay attention when you configure when Access Switch fe0/1 connects to Distribution Switch fe0/8 or something weird on one switch and then Access Switch fe0/5 connects to Distribution Switch fe0/12 on the other.

There is however still a catch to this lab layout, notice that from DSW1 to DWS2 the connections flip and the same applies to the ASW1 and ASW2 (meaning DSW1 fe0/1 connects to ASW1 while DSW2 fe0/1 connects to ASW2). Something that means I have to stay awake but not on my toes.

Initial Configuration

The initial configuration entails some things old (CCNA) and some one new command (not drastically new). I am going to go through what I am doing to practice for the exam and annotate the commands and generally what they do.

I am a weird Muppet, I want to know what and more importantly why something has to be used (probably the reason it takes me so long to study things). I can’t make sense of something unless I know command X is used to enable/do Y and relates to the theory in such and such a fashion for a particular reason.

Distribution Switch 1

Step 1: Setup the basics all of the following is CCNA level stuff and should easy if not second nature. This is to get the security and host name down before going onto the interface configuration.

Enter Privileged Mode switch>enable Enter Global Configuration Mode switch#configure terminal Change the hostname of the switch switch(config)#hostname DSW1 Enable secret and password DSW1(config)#enable secret ciscosystems DSW1(config)#enable password cisco Setup a local user database DSW1(config)#username admin@mydomain.com privilege 15 password cisco Setup the console port password DSW1(config)#line con 0 DSW1(config-line)#login local DSW1(config-line)#exit Setup the Virtual Teletype Terminal (VTY) Password DSW1(config)#line vty 0 4 DSW1(config-line)#password cisco DSW1(config-line)#login DSW1(config-line)#exit Setup the Auxiliary Password DSW1(config)#line aux 0 DSW1(config-line)#no exec DSW1(config-line)#exit

Step 2: Setup the management interface

Setup the default VLAN ip address from remote ip admin if there was a GUI and to Telnet to the switch DSW1(config)#interface vlan 1 DSW1(config-if)#ip address 192.168.1.1 255.255.255.0 DSW1(config-if)#no shut DSW1(config-if)#exit

Step 3: Setup other interfaces

Setup Fastethernet Interfaces DSW1(config)#interface fastethernet 0/1 DSW1(config-if)#description DSW1 - ASW1 DSW1(config-if)#speed 100 DSW1(config-if)#duplex auto DSW1(config-if)#no shut DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/2 DSW1(config-if)#description DSW1 - ASW1 DSW1(config-if)#speed 100 DSW1(config-if)#duplex auto DSW1(config-if)#no shut DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/3 DSW1(config-if)#description DSW1 - ASW2 DSW1(config-if)#speed 100 DSW1(config-if)#duplex auto DSW1(config-if)#no shut DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/4 DSW1(config-if)#description DSW1 - ASW2 DSW1(config-if)#speed 100 DSW1(config-if)#duplex auto DSW1(config-if)#no shut DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/11 DSW1(config-if)#description DSW1 - DSW2 DSW1(config-if)#speed 100 DSW1(config-if)#duplex auto DSW1(config-if)#no shut DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/12 DSW1(config-if)#description DSW1 - DSW2 DSW1(config-if)#speed 100 DSW1(config-if)#duplex auto DSW1(config-if)#no shut DSW1(config-if)#exit

Alternatively use range command

Setup Fastethernet Interfaces DSW1(config)#interface fastethernet 0/1 DSW1(config-if)#description DSW1 - ASW1 DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/2 DSW1(config-if)#description DSW1 - ASW1 DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/3 DSW1(config-if)#description DSW1 - ASW2 DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/4 DSW1(config-if)#description DSW1 - ASW2 DSW1(config-if)#exit DSW1(config)#interface range fastethernet 0/1 - 4 DSW1(config-if-range)#speed 100 DSW1(config-if-range)#duplex auto DSW1(config-if-range)#no shut DSW1(config-if-range)#exit DSW1(config)#interface fastethernet 0/11 DSW1(config-if)#description DSW1 - DSW2 DSW1(config-if)#exit DSW1(config)#interface fastethernet 0/12 DSW1(config-if)#description DSW1 - DSW2 DSW1(config-if)#exit DSW1(config)#interface range fastethernet 0/11 - 12 DSW1(config-if-range)#speed 100 DSW1(config-if-range)#duplex auto DSW1(config-if-range)#no shut DSW1(config-if-range)#exit

Step 4: Shut down non-used interfaces

Aministratively shut down all ports not connected DSW1(config)#interface range fastethernet 0/5 - 10 DSW1(config-if-range)#shut DSW1(config-if-range)#exit Exit Global Configuration Mode DSW1(config)#exit

Step 5: Check your work

Check that you named the interfaces correctly, havent missed out on a connected interface and that the duplex and speed setting are correct DSW1#show interfaces status show run the running configuration DSW1#show run

Step 6: Save your work

Copy the running configuration to the startup configuration. I got in the bad habbit to do this the other way around for a while (did it in an exam)... oops copy start run DSW1#copy run start

Distribution Switch 2

Enter Privelaged Mode switch>enable Enter Global Configuration Mode switch#configure terminal Change the hostname of the switch switch(config)#hostname DSW2 Enable secret and password DSW2(config)#enable secret cisco DSW2(config)#enable password cisco Setup a local user database DSW2(config)#username admin@mydomain.com privilege 15 password cisco Setup the console port password DSW2(config)#line con 0 DSW2(config-line)#login local DSW2(config-line)#exit Setup the Virtual Teletype Terminal (VTY) Password DSW2(config)#line vty 0 4 DSW2(config-line)#password cisco DSW2(config-line)#login DSW2(config-line)#exit Setup the Auxiliary Password DSW2(config)#line aux 0 DSW2(config-line)#no exec DSW2(config-line)#exit

Step 2: Setup the management interface

Setup the default VLAN ip address from remote ip admin if there was a GUI and to Telnet to the switch DSW2(config)#interface vlan 1 DSW2(config-if)#ip address 192.168.1.50 255.255.255.0 DSW2(config-if)#no shut DSW2(config-if)#exit

Step 3: Setup other interfaces

Setup Fastethernet Interfaces DSW2(config)#interface fastethernet 0/1 DSW2(config-if)#description DSW2 - ASW2 DSW2(config-if)#speed 100 DSW2(config-if)#duplex auto DSW2(config-if)#no shut DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/2 DSW2(config-if)#description DSW2 - ASW2 DSW2(config-if)#speed 100 DSW2(config-if)#duplex auto DSW2(config-if)#no shut DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/3 DSW2(config-if)#description DSW2 - ASW1 DSW2(config-if)#speed 100 DSW2(config-if)#duplex auto DSW2(config-if)#no shut DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/4 DSW2(config-if)#description DSW2 - ASW1 DSW2(config-if)#speed 100 DSW2(config-if)#duplex auto DSW2(config-if)#no shut DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/11 DSW2(config-if)#description DSW2 - DSW1 DSW2(config-if)#speed 100 DSW2(config-if)#duplex auto DSW2(config-if)#no shut DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/12 DSW2(config-if)#description DSW2 - DSW1 DSW2(config-if)#speed 100 DSW2(config-if)#duplex auto DSW2(config-if)#no shut DSW2(config-if)#exit

Alternatively use range command

Setup Fastethernet Interfaces DSW2(config)#interface fastethernet 0/1 DSW2(config-if)#description DSW1 - ASW1 DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/2 DSW2(config-if)#description DSW1 - ASW1 DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/3 DSW2(config-if)#description DSW1 - ASW2 DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/4 DSW2(config-if)#description DSW1 - ASW2 DSW2(config-if)#exit DSW2(config)#interface range fastethernet 0/1 - 4 DSW2(config-if-range)#speed 100 DSW2(config-if-range)#duplex auto DSW2(config-if-range)#no shut DSW2(config-if-range)#exit DSW2(config)#interface fastethernet 0/11 DSW2(config-if)#description DSW1 - DSW2 DSW2(config-if)#exit DSW2(config)#interface fastethernet 0/12 DSW2(config-if)#description DSW1 - DSW2 DSW2(config-if)#exit DSW2(config)#interface range fastethernet 0/11 - 12 DSW2(config-if-range)#speed 100 DSW2(config-if-range)#duplex auto DSW2(config-if-range)#no shut DSW2(config-if-range)#exit

Step 4: Shut down non-used interfaces

Aministratively shutdown all ports not connected DSW2(config)#interface range fastethernet 0/5 - 10 DSW2(config-if-range)#shut DSW2(config-if-range)#exit Exit Global Configuration Mode DSW2(config)#exit

Step 5: Check your work

Check that you named the interfaces correctly, havent missed out on a connected interface and that the duplex and speed setting are correct DSW2#show interfaces status show run the running configuration DSW2#show run

Step 6: Save your work

Copy the running configuration to the startup configuration. I got in the bad habbit to do this the other way around for a while (did it in an exam)... oops copy start run DSW2#copy run start

Access Switch 1

Enter Privelaged Mode switch>enable Enter Global Configuration Mode switch#configure terminal Change the hostname of the switch switch(config)#hostname ASW1 Enable secret and password ASW1(config)#enable secret cisco ASW1(config)#enable password cisco Setup a local user database ASW1(config)#username admin@mydomain.com privilege 15 password cisco Setup the console port password ASW1(config)#line con 0 ASW1(config-line)#login local ASW1(config-line)#exit Setup the Virtual Teletype Terminal (VTY) Password ASW1(config)#line vty 0 4 ASW1(config-line)#password cisco ASW1(config-line)#login ASW1(config-line)#exit Setup the Auxiliary Password ASW1(config)#line aux 0 ASW1(config-line)#no exec ASW1(config-line)#exit

Step 2: Setup the management interface

Setup the default VLAN ip address from remote ip admin if there was a GUI and to Telnet to the switch ASW1(config)#interface vlan 1 ASW1(config-if)#ip address 192.168.1.100 255.255.255.0 ASW1(config-if)#no shut ASW1(config-if)#exit

Step 3: Setup other interfaces

Setup Fastethernet Interfaces ASW1(config)#interface fastethernet 0/1 ASW1(config-if)#description ASW1 - DSW1 ASW1(config-if)#speed 100 ASW1(config-if)#duplex auto ASW1(config-if)#no shut ASW1(config-if)#exit ASW1(config)#interface fastethernet 0/2 ASW1(config-if)#description ASW1 - DSW1 ASW1(config-if)#speed 100 ASW1(config-if)#duplex auto ASW1(config-if)#no shut ASW1(config-if)#exit ASW1(config)#interface fastethernet 0/3 ASW1(config-if)#description ASW1 - DSW2 ASW1(config-if)#speed 100 ASW1(config-if)#duplex auto ASW1(config-if)#no shut ASW1(config-if)#exit ASW1(config)#interface fastethernet 0/4 ASW1(config-if)#description ASW1 - DSW2 ASW1(config-if)#speed 100 ASW1(config-if)#duplex auto ASW1(config-if)#no shut ASW1(config-if)#exit

Alternatively use the range command

Setup Fastethernet Interfaces ASW1(config)#interface fastethernet 0/1 ASW1(config-if)#description DSW1 - ASW1 ASW1(config-if)#exit ASW1(config)#interface fastethernet 0/2 ASW1(config-if)#description DSW1 - ASW1 ASW1(config-if)#exit ASW1(config)#interface fastethernet 0/3 ASW1(config-if)#description DSW1 - ASW2 ASW1(config-if)#exit ASW1(config)#interface fastethernet 0/4 ASW1(config-if)#description DSW1 - ASW2 ASW1(config-if)#exit ASW1(config)#interface range fastethernet 0/1 - 4 ASW1(config-if-range)#speed 100 ASW1(config-if-range)#duplex auto ASW1(config-if-range)#no shut ASW1(config-if-range)#exit

Step 4: This is where the ASW and the DSW switches differ. This connects to the Workstation end-point where the DSW switches use port 11/12 to provide failover for the distribution

Setup Fastethernet 0/12 for 10mbs half duplex as an access level end-point interface ASW1(config)#interface fastethernet 0/12 ASW1(config-if)#description ASW1 - PC1 ASW1(config-if)#speed 10 ASW1(config-if)#duplex half Make the port as an access port ASW1(config-if)#switchport mode access ASW1(config-if)#no shut ASW1(config-if)#exit

Step 5: Shut down non-used interfaces

Aministratively shutdown all ports not connected ASW1(config)#interface range fastethernet 0/5 - 11 ASW1(config-if-range)#shut ASW1(config-if-range)#exit Exit Global Configuration Mode ASW1(config)#exit

Step 5: Check your work

Check that you named the interfaces correctly, havent missed out on a connected interface and that the duplex and speed setting are correct ASW1#show interfaces status show run the running configuration ASW1#show run

Step 6: Save your work

Copy the running configuration to the startup configuration. I got in the bad habbit to do this the other way around for a while (did it in an exam)... oops copy start run ASW1#copy run start

Access Switch 2

Enter Privelaged Mode switch>enable Enter Global Configuration Mode switch#configure terminal Change the hostname of the switch switch(config)#hostname ASW2 Enable secret and password ASW2(config)#enable secret cisco ASW2(config)#enable password cisco Setup a local user database ASW2(config)#username admin@mydomain.com privilege 15 password cisco Setup the console port password Setup the console port password ASW2(config)#line con 0 ASW2(config-line)#login local ASW2(config-line)#exit Setup the Auxiliary Password ASW2(config)#line aux 0 ASW2(config-line)#no exec ASW2(config-line)#exit Setup the Virtual Teletype Terminal (VTY) Password ASW2(config)#line vty 0 4 ASW2(config-line)#password cisco ASW2(config-line)#login ASW2(config-line)#exit

Step 2: Setup the management interface

Setup the default VLAN ip address from remote ip admin if there was a GUI and to Telnet to the switch ASW2(config)#interface vlan 1 ASW2(config-if)#ip address 192.168.1.200 255.255.255.0 ASW2(config-if)#no shut ASW2(config-if)#exit

Step 3: Setup other interfaces

Setup Fastethernet Interfaces ASW2(config)#interface fastethernet 0/1 ASW2(config-if)#description ASW2 - DSW2 ASW2(config-if)#speed 100 ASW2(config-if)#duplex auto ASW2(config-if)#no shut ASW2(config-if)#exit ASW2(config)#interface fastethernet 0/2 ASW2(config-if)#description ASW2 - DSW2 ASW2(config-if)#speed 100 ASW2(config-if)#duplex auto ASW2(config-if)#no shut ASW2(config-if)#exit ASW2(config)#interface fastethernet 0/3 ASW2(config-if)#description ASW2 - DSW1 ASW2(config-if)#speed 100 ASW2(config-if)#duplex auto ASW2(config-if)#no shut ASW2(config-if)#exit ASW2(config)#interface fastethernet 0/4 ASW2(config-if)#description ASW2 - DSW1 ASW2(config-if)#speed 100 ASW2(config-if)#duplex auto ASW2(config-if)#no shut ASW2(config-if)#exit

Alternatively use the range command

Setup Fastethernet Interfaces ASW2(config)#interface fastethernet 0/1 ASW2(config-if)#description DSW1 - ASW1 ASW2(config-if)#exit ASW2(config)#interface fastethernet 0/2 ASW2(config-if)#description DSW1 - ASW1 ASW2(config-if)#exit ASW2(config)#interface fastethernet 0/3 ASW2(config-if)#description DSW1 - ASW2 ASW2(config-if)#exit ASW2(config)#interface fastethernet 0/4 ASW2(config-if)#description DSW1 - ASW2 ASW2(config-if)#exit ASW2(config)#interface range fastethernet 0/1 - 4 ASW2(config-if-range)#speed 100 ASW2(config-if-range)#duplex auto ASW2(config-if-range)#no shut ASW2(config-if-range)#exit

Step 4: This is where the ASW and the DSW switches differ. This connects to the Workstation end-point where the DSW switches use port 11/12 to provide failover for the distribution

Setup Fastethernet 0/12 for 10mbs half duplex as an access level end-point interface ASW2(config)#interface fastethernet 0/12 ASW2(config-if)#description ASW2 - PC2 ASW2(config-if)#speed 10 ASW2(config-if)#duplex half ASW2(config-if)#no shut Make the port as an access port ASW2(config-if)#switchport mode access ASW2(config-if)#exit

Step 5: Shut down non-used interfaces

Aministratively shutdown all ports not connected ASW2(config)#interface range fastethernet 0/5 - 11 ASW2(config-if-range)#shut ASW2(config-if-range)#exit Exit Global Configuration Mode ASW2(config)#exit

Step 5: Check your work

Check that you named the interfaces correctly, havent missed out on a connected interface and that the duplex and speed setting are correct ASW2#show interfaces status show run the running configuration ASW2#show run

Step 6: Save your work

Copy the running configuration to the startup configuration. I got in the bad habbit to do this the other way around for a while (did it in an exam)... oops copy start run ASW2#copy run start

For more information on Commands and why to use a command in a certain place check out the Cisco Command lookup tool (CCO Login required)

Cisco CDP

In a LAB or Real World (RW) situation you would telnet or console into Distribution Switch 1 (DSW1) and work from there. First off I am going to use CDP to discover the network topology. This is old work from the CCNA and useful if you (1) don’t know the network topology, (2) remote into a network to do work and need to hop from one device to another and need network information, (3) have a huge network and never bothered to document growth (ISPs), or (4) you are too lazy or there is a foot thick metal vault door between you and the kit and changing the console cable from one switch/router to another one isn’t going to happen.

The following command gives a basic table of information,
DSW1#show cdp neighbors
To get specific information use,
DSW1#show cdp neighbors detail
With that information you can then do something like this:
DSW1#telnet 192.168.1.50 Trying 192.168.1.50 ... Open User Access Verification Password:_ DSW2#

Terminology:

Two terms that I have been made aware of recently that I need to remember out-of-band management and in-band management.

Out-of-Band Management is the use of a dedicated channel for device maintenance. Example of this would be using the Console port (Serial) or maybe the Auxiliary port (modem – pots – offsite) for management purposes.

In-Band Management is the use of regular channels for device maintenance. Example of this would be using Ethernet for Console Access (when you change the IP Address the session ends).

Notes and Notices:

This is a part of my personal BCMSN notes and research to assist myself in learning and understanding the concepts and theory for the BCMSN exam. I learn by making notes reading and writing things down and wish to file them where I can’t lose them. These notes are not to be seen, judged or mistaken for replacements to Cisco recognized and authorized training which I personally support and attend and suggest you undertake if you are going for the BCMSN Certification.

Planning Voice on a Data Network

Published

Deon Botha

on May 21, 2008

in BCMSN, Certification, Cisco Systems and VoIP

. 0 Comments

There are numerous benefits to packet switched telephony:

More efficient use of bandwidth and kit: Traditional telephony networks use a 64-kbps (For argument lets say 1B Channel on a ISDN line) channel for every voice call. Packet telephony shares bandwidth among multiple logical connections and offloads traffic volumes from existing voice switches.
Lower costs for telephony network transmissions: A substantial amount of equipment is needed to combine 64-kbps (ISDN) channels into a high-speed link for transport across a network (Lets say an ISDN PRI). Packet telephony statistically multiplexes voice traffic alongside data traffic. This consolidation represents substantial savings on CAPEX and OPEX.
Consolidated voice and data network expenses: Data networks functioning separately from voice networks become major traffic carriers. The underlying voice networks can be converted to utilize the packet-switched architecture to create a single integrated communications network with a common switching and transmission system. The benefit is CAPEX and OPEX savings.
Increased revenues from new services: Packet telephony enables new integrated services, such as broadcast-quality audio, unified messaging, and real-time voice and data collaboration. These services increase employees productivity and profit margins well above those of basic voice services. In addition, these services enable companies and service providers to differentiate themselves and improve their market position.
Greater innovation in services: Unified communications use the IP infrastructure to consolidate communications methods that were previously independent (Fax, voicemail, email, wireline telephone, cellular phone, and the web). The IP Infrastructure provides users with a common method to access messages and initiate real-time communications – independent of time, location, or device.
Adding to new communications devices acket technology can reach devices that are largely inaccessible to the time-division multiplexing (TDM) infrastructures of today (pcs, wireless devices, household appliances, PDAs). Access to these devices enable companies and service providers to increase the volume of communications they deliver, the breadth of service they offer, and the number of subscribers they serve. Packet technology, therefore, enables companies to market new devices, including videophones, multimedia terminals, and advanced IP Phones.
Flexible new pricing structures: Companies and services providers with packet-switched networks can transform their service and pricing models. Because network bandwidth can be dynamically allocated, network usage no longer needs to be measured in minutes or distance. Dynamic allocation gives service providers the flexibility to meet the needs of their customers in ways that bring them the greatest benefits.

The basic components for voice on a IP network are as follows:

IP Phones: The end-device on desks
Gatekeeper: Provides Connection Admission Control (CAC), bandwidth control and management and address translation.
Gateway: Provides translation between voice over Internet Protocol (VoIP) and non-VoIP networks, such as the public switched telephone network (PSTN). It provides physical access for local analog and digital devices (telephones, fax machines, and PBXs)
Multipoint Control Unit: Provides real-time connectivity for participants in multiple locations to attend the same videoconference or meeting.
Call Agent: Provides call control for IP Phones, CAC, bandwidth control and management, and address translation.
Application Server: Provides services such as voicemail, unified messaging, and Cisco CallManager Attendant Console.
Videoconference Station: Provides access for end-users participation in videoconferencing. This station has a video camera and a microphone. The user can view video streams and hear the audio that originates from the remote user station.

There are other components not listed here like voice applications, interactive voice response (IVR) systems, and softphones that meet the specific needs of enterprise.

Voice and Data Traffic Characteristics

Voice traffic has extremely stringent QoS requirements (because it is extremely delay sensitive). Voice traffic generates a smooth demand on bandwidth and has minimal impact on other traffic (60 – 120 bytes), as long as voice traffic is managed. Because of the resulting time sensitive nature User Datagram Protocol (UDP) is used to package voice packets; TCP retransmit capabilities have no value (because if it needs to be retransmitted then there is delay in the actual conversation occuring NOW).

For voice quality, delay should be no more than 150ms (one-way) and less than 1% packet loss. A typical voice call requires 17 – 106 kbps of guaranteed priority bandwidth, plus additional 150bps per call for voice-control traffic. Multiplying this out for the maximum calls expected during busiest times the overall bandwidth requirements for voice traffic can be calculated.

Because Data traffic is not as delay sensitive and can tolearate high drop rates the restransmit capabilities of TCP has become important, as a result many applications use by default TCP.

In networks, important business critical applications are ussually easy to identify. Most applications can be identified based on TCP or UDP port numbers (HTTP, HTTPS, FTP, TELNET, SQL, ETC). Some application use dynamic port numbers that, to some extent, make classification more difficult. Cisco IOS software supports network-based application recognition (NBAR), which can be used to recognize dynamic port applications.

VoIP Call Flow

As I mentioned in a previous post (see HSRP Accross Trunk Links) and some other places its best practice to setup voice and data on separate VLANs (I did in my own network). This is done so that QoS can be applied to prioritize the VoIP traffic as it traverses the network. If this is not done then voice and data traffic contend for available traffic without consideration for other devices (one or the other is going to suffer).

A major component of designing a successful IP Telephony network is bandwidth provisioning. The bandwidth requirement is calculated by adding the total required bandwidth for voice, video and data together; the sum should not be more than 75% of the link total.

For a traffic perspective IP Telephony consists of two types of traffic:

Voice Carrier Stream consists of Real-Time Transport Protocol (RTP) packets that contain actual voice samples.
Call Control Signaling that contains packets belonging to one of several protocols used to set up, maintain, tear down, or redirect calls. Depending on the end-point this could be H.323 or Media Gateway Control Protocol (MGCP)

Auxiliary VLANs

Some Cisco Catalyst switches offer a unique feature called “Auxiliary VLAN“. This feature allows one to overlay a voice topology over an existing data network. One can segment phones into a separate logical network, even though the data and voice network are physically the same.

The auxiliary VLAN feature places the phones into their own VLANs without any end-user configuration. Additionally VLAN assignment can be maintained even if the phone is moved.

How this works is that when a phone is plugged into the switch (whichever port), the phone will request a DHCP address, and the phone is placed in a VLAN automatically. With phones in their own VLANs administrators can troubleshoot and identify problems easily. This also makes enforcement of QoS and security policies easier.

QoS

QoS is the application of features and functionality required to actively manage and satisfy the networking requirements of applications that are sensitive to loss, delay and delay variations (jitter). QoS allows preference to be given to critical application flows for the available bandwidth.

Cisco IOS implementations allows for QoS to provid these features:

Priority access to resources: QoS allows administrators to control which traffic it allows to access specific network resources such as bandwidth, kit, and WAN links.
Efficient management of network resources: If network management and accounting tools indicate that specific traffic is experiencing latency, jitter, and packet loss, then QoS tools can be used to adjust how traffic is handled.
Tailored service: The control provided by QoS enables Internet Service Providers to offer carefully tailored grades of service to their customers.
Coexistance of mission-citical applications: QoS technologies ensure that mission-critical applications receive priority access to network resources while providing adequate processing for applications that are not delay sensitive.

High Availability

Traditional Telephony networks strive to provide 99.999 (5.25 minutes) of downtime a year. This is less downtime than most data networks. To provide the same experience this means choosing hardware and software with a low mean time between failure (MTBF) or installing redundant links and hardware.

Availability is when a user wants to make a call the network is able to respond to that need. Efforts to ensure availability would include proactive management to predict failure and taking steps to correct problems in design of the network as it grows. When the converged network goes down things downtime can be minutes, hours or days. This is unacceptable in a converged network where downtime means no phone calls. Providing for uninterpretable power supplies (UPS), lighting arrestors and other means to ensure availability at all costs.

High Availability encompases many areas of a network. In a fully redundant network these components need to be duplicated:

Servers and call managers,
Acces layer devices (layer-2 switches)
Distribution layer devices (routers or Layer-3 switches)
Core layer devices (layer-3 switches)
Interconnections (WAN links, PSTN Gateways, ISP links)
Power supplies and UPSs

Notes and Notices:

WLAN Standards

Published

Deon Botha

on May 15, 2008

in 802.11, Access Point, BCMSN, Certification, Cisco Systems, Concepts and Constructs and Wireless

. 0 Comments

This is a generally a nice to know topic; if you don’t want to know the basics on “how” it works but rather just care that it works this might not be “light” reading.

There are “generally” (dependant on your country) unlicensed bands:

900-MHz Industrial, Scientific and Medical (ISM) Band (902-MHz to 928-MHz)
2.4-GHz Industrial, Scientific and Medical (ISM) Band (2400-MHz to 2483-MHz) (Japan to 2495-MHz)
5.7-GHz Unlicensed National Information Infrastructure (UNII) Band (5150-MHz to 5350/5725/5825 MHz) (Not all countries support 802.11a)

Radio Frequency Transmission (for dummies i.e. with no electric/electronic engineering background a.k.a ME):

Radio Frequencies (RF) are radiated (why does this not make me feel better I’ve seen what a microwave do when it radiates things) into the air by antennas that create radio waves. When radio waves are propagated through objects, they may be absorbed (walls) or reflected (metal). This absorption may cause areas of low-signal.

Radio wave transmission is affected by the three factors:

Reflection: when RF waves bounce of objects (metal, glass)
Scattering: when RF waves strike uneven surfaces and are reflected in many directions
Absorption: when RF waves are absorbed by objects (concrete, bricks, walls)

Data Transmission over Radio Waves (for dummies i.e. with no eletric/electronic engineering background a.k.a ME):

Higher data rates (faster connection) have shorter range because the receiver needs a stronger signal with a better signal-to-noise ratio (SNR) to retrieve the information.
Higher transmit power results in greater range. To double the range, the power has to be increased by a factor of 4 (four).
Higher data rates require more bandwidth. Increased bandwidth is possible with higher frequencies.
Higher frequencies have shorter range through higher degradation and absorption. More efficient antennas can compensate for this effect.

WLAN Regulations and Standardizations:

Regulatory Agencies control the use and enjoyment of RF bands. The two main regulatory agencies are the FCC (USA) and ETSI (Europe) (South Africa and EMEA region if in doubt follow ETSI).

The network (802) standardization is done by the IEEE. The wireless (802.11) standards are part of the network standard these include 802.11 a/b/g and soon to be finalized/ratified n.

Finally the Wi-Fi Alliance offers certification for vendors of 802.11 products so that their products are interoperable. The Wi-Fi Alliance certifications include all three 802.11 RF technologies and Wi-Fi Protected Access (WPA) security model (2003) based on IEEE 802.11i (ratified 2004).

IEEE 802.11b

Ratified Sept 1999

Operates in the 2.4-GHz ISM Band

Specifies direct sequence spread spectrum (DSSS)

Specifies four data rates up to 11-Mbps (1, 2, 5.5, and 11-Mbps)

Throughput Mbps * 1024/Users = X kbps Bandwidth per user

2.4-GHz Channels

Up until this point Wireless channels might not have made “sense” if you weren’t as I joked “previously advantaged” with a electrical or electronic engineering qualification. Those ladies and gents are force fed this amongst other things for at the very least a semester in university so they know this kind of thing backwards (I know how they complained about it). If you are like myself a business grad then this is all new.

What this graph shows (pay attention to the grey highlight) is 3 non-overlapping Channels (except for Japan). If you are in Japan you can use the 14th channel along with 3 others to have access to 4 total channels.

This information is region specific and then also country specific (I know South Africa in general follows ETSI which falls under EMEA). Some countries may allow 14 channels while others may only allow 1 channel.

At a Cisco Tech-Update (I can’t remember the speaker forgive me) Wireless channel usage was explained using the below diagram and it made all the above fall into place for me.

What the diagram shows is the 2.4-Ghz frequency (visually) with the channels laid out how all the channels overlap. This is what 802.11 b/g “looks” like with the 3 non-overlapping channels (black).

Example: Three non-overlapping channels (1, 6, and 11) that do not share RFs. There would be no degradation in throughput if 3 APs were to operate in the same cell using channels 1, 6, and 11.

To show the maths 3 APs on 3 non-overlapping channels (2, 6, and 11) provide an aggregate data-rate for a cell of 33-Mbps (11-Mbps x 3), with an aggregated throughput of approx. 16-Mbps (33-Mbps/2).

Example: Three APs sharing the same channel, in the same cell.

To show the math 3 APs on the same channel(1, 1, and 1) provide an aggregate data rate a 11-Mbps but an aggregated throughput of 6-Mbps. This results from APs sharing a cell.

Example: Three APs sharing overlapping channels, in the same cell.

To show the math 3 APs on overlapping channels (1, 2, and 3) the throughput could drop to well below 1-Mbps due to interference.

Channel Reuse

At the same Tech Update they explained how using the non-overlapping channels a deployment can be done where none of the same channels border. Imagine the cells from top down on an overaly of an office plan looking like the diagram below.

Data Rates

WLAN clients (end-devices) can shift data rates as they move. The closer you are to a AP the better coverage will be (11-Mbps), as you move away from the AP coverage will get worse (5.5-Mbps) and worse (2-Mbps) and worse (1-Mbps) until there is no signal. This data rate shifting occurs without user interaction or connection loss.

This rate shifting also happens on a transmission-by-transmission basis; whereby the AP can support multiple clients at multiple speeds (meaning transmissions 1 might be 11-Mbps and transmission 2 might be 1-Mbps depending on the end-user location).

IEEE 802.11a

Ratified Sept 1999

Operates in the 5-GHz ISM Band

Uses orthogonal frequency-division multiplexing (OFDM)

Specifies eight data rates up to 54-Mbps (6, 9, 12, 18, 24, 36, 48, 54-Mbps)

FCC – 12 to 23 non-overlapping channels

ETSI – up to 19 non-overlapping channels

Regulatory differences across countries

802.11a requires Transmit (Tx) power control and dynamic frequency selection (802.11h)

Throughput Mbps * 1024/Users = X kbps Bandwidth per user

5-GHz Channels

802.11a must comply with two features in 802.11h namely Transmit Power Control (TPC) and Dynamic Frequency Selection (DFS).

TPC links back to the basics, the more Transmit Power pumped into an AP the greater the range (greater range = less data-rate). TPC is where an AP exchanges transmit power information with end-device adapters. This has a twofold advantage:

end-device adapters use only enough power to maintain association with APs at any given data rate. In turn conserving energy (good for mobile devices and at current Eksom).
end-devices contribute less to adjacent cell interference.

DFS is where the AP monitors the available 5-Ghz RF spectrum radar installations in the environment and if found flags the appropriate channel(s) as unavailable. DFS continually monitors the operating environment for changes during operation.

IEEE 802.11g

Ratified June 2003

Operates in the 2.4-GHz ISM Band as 802.11b

Uses direct sequence spread spectrum (DSSS) complementary code keying (CKK) and orthogonal frequency-division multiplexing (OFDM)

Specifies twelve data rates up to 54-Mbps (1, 2, 5.5, 11-Mbps DSSS/802.11b and 6, 9, 12, 18, 24, 36, 48, 54-Mbps OFDM).

Throughput Mbps * 1024/Users = X kbps Bandwidth per user

Security and Mitigation of Wireless Risks

Linking back to the beginning of this post and why Wireless could potentially be a security threat. The process of Wireless is “Radio Frequencies (RF) (that) are radiated into the air by antennas that create radio waves” and in turn your network data travels across radio waves from source (server or point A) to destination (end-device or point B).

This wireless communication if left unsecured, leaves a wide open method of access to anyone that wants to enter, use and abuse your enterprise infrastructure. With the low cost of IEEE 802.11 wireless equipment these days adoption is gaining in the mass market (home, small office/home office (SOHO), small medium business (SMB)). With greater adoption of the mass market the products are easier to use and deploy and implement (graphical user interface (GUI) deployments and out the box operation). This large adoption also makes for sub-business class consumer grade products making a regular appearance in server-rooms, business settings and other environments where they are definitely not meant to be (don’t get me wrong consumer products work great for a family of 5 people but aren’t built or designed to handle with an office of 10 people or a department of 50 people).

There are many large telco (Telkom) companies that offer pre-configured Wi-Fi combination routers with the DSL accounts. Most if not the majority of users literally plug and play (plug it in and use it with default settings). This is a very conducive environment for “war driving” for the single purpose of free Internet, collecting sensitive information through the use of various freely available tools and applications.

The Process

Anyone implementing Wireless needs to at the very least consider security which is a three step process of Authentication (802.1x or Extensible Authentication Protocol (EAP)), Encryption (Wi-Fi Protected Access (WPA – TKIP, WPA2 – AES or TKIP)) and Intrusion Detection and Protection (IDS and IPS).

Wireless Association

Looking at how end-devices (clients like notebooks, smartphones, PDAs) associate with APs then something I mentioned in a previous post will crystallize.

APs broadcast (send out) beacons with SSIDs (one or many), data rates (depending on distance from AP) and other information. The end-device scans the available channels looking for beacons and responses from APs. The end-device then in turn associates with the AP with the strongest signal.

If you are using a mobile device and moving with your device and signal becomes weak this process will repeat.

It is during this association process that SSID, MAC address and security settings are sent from end-device to the AP and checked. This is what we are going to be talking about in the next couple of paragraphs.

Authentication

When an end-device attempts to associate this is done via the 802.1x protocol. The end-device is called a supplicant which communicates with an autonomous AP* (called the authenticator) that communicates and in turn authenticates to an Authentication, Authorization and Accounting Server (AAA Server) like RADIUS/TACACS+ or Cisco Secure ACS.

*LWAPP uses the WLAN controller that acts as the Athenticator that in turn communicates and authenticates with the AAA Server.

Encryption

After authentication is successful (if unsuccessful the connection is denied) data between the end-device and the AP is sent encrypted in either TKIP or AES encryption.

Definitions

Signal-to-Noise

Notes and Notices:

WLAN Infrastructure Topologies

Published

Deon Botha

on May 14, 2008

in 802.11, Access Point, BCMSN, Certification, Cisco Systems, Concepts and Constructs and Wireless

. 2 Comments

As talked about in the previous post the difference between a wired LAN and a Wireless Local Area Networks (WLANs) is that the Layer-1 transmission medium of a traditional wired local area network (LAN) (CAT-5 cable) is replaced with Radio Frequency (RF) transmissions.

What follows is the pimping of Cisco Aironet products and where they fit into three main wireless categories:

Wireless in-building LANs for client Access: The Cisco Aironet products can plug into an existing wired infrastructure and function like an overlay to the existing LAN or even replace the wired LAN.

Wireless Building-to-Building bridges: The Cisco Aironet products can provide wireless bridging to connect two or more networks that are physically separated to be connected on one LAN without the time or expense required to get physical lines to be installed.

Wireless mesh networks: Mesh networking is a mixture of the above two categories. Mesh networking provide dynamic, redundant, fault-tolerant links for building and client access.

Service Set Identifier (SSID)

Myth: Hidden (not broadcasting) the SSID makes a wireless network secure.

The SSID is the “name” of a wireless cell, this name is used to logically separate WLANs. The SSID must match exactly between the client and the access point for them to connect. The Access Point (AP) sends the SSID out in beacons.

The beacons are broadcasts that an AP sends to advertise available services, these beacons go out whether SSID is hidden or not (Clients can be configured without a SSID, where they learn the SSID from the beacons of the AP).

The Topology Basic

Extended Services Set: Two or more Basic Serve sets (Mobile clients use a single AP to connect) are connected by a common distribution system (backbone) An Extended Service Set includes a common SSID to allow roaming from AP to AP without client config.

The diagram shows the WLAN topology with 2 APs and some devices (Microsoft Icons) that I know to be Wi-Fi capable (from left to right tablet notebook, projector, PDA, smartphone, notebook).

Wireless Cell: The basic area is the RF coverage provided by an AP (Channel 1 or Channel 2 NOT both). This area is also called the “microcell“. To extend/enlarge/make bigger the basic area one simply adds APs (Recently microcell has moved to picocell reducing AP coverage by reducing power and increasing total number of AP deployed).

The basic area of an AP is called the service set, the basic area of the combined APs is called the extended services set (There is a recommended 10 – 15 % overlap between cells for data networks to allow roaming without losing RF connection. There is a 15 – 20% overlap for voice/data/video networks). Bordering cells should be set to different non-overlapping channels for best performance (more on this later).

Access Point: The name is self explanatory reverse the name Point “of” Access. As the name denotes this is the point at which client-devices connect/access the wireless network. The APs connect to then to the Ethernet backbone and facilitate the communication between wired and wireless networks

The AP is the master of a given cell and manages/controls traffic to and from the network (remote devices do not communicate with each other they communicate through the AP).

Picocell: the benefit of a picocell is better coverage, less interference, higher data rates, and fault tolerance through convergence. When an AP goes down, the neighbouring AP expands coverage by increasing power (this increases the RF range) to cover for the lost AP. (Look into WLAN Controllers cause this gets complicated to do manually quickly with say more than 5 APs)

Wireless Repeater

In environments (factory floors, doctors room, large retail, wholesale storehouses) where its just not practical to put down a wired LAN or the application of the network wouldn’t work with a wired system a wireless repeater can be put down.

A wireless repeater is a AP that is not connected to the Wired LAN (Requires 50% overlap of the AP on the Wired LAN side). This setup however has a large throughput impact where throughput is decreased by half due to the receive and retransmit time.

The SSID of the AP (the one on the left) must be configured on the wireless repeater (the one on the right). The wireless repeater uses the same channel as the AP (NB not all implementations support this).

Workgroup Bridge

Cisco Wireless Workgroup Bridge (WGB) (Reference Cisco Q&A Document) that connects to the Ethernet (RJ-45) port of any end-device (if it has a Ethernet port and is therefore network-able) that doesn’t have a WLAN Network Interface Card (NIC) (either because the end-device doesn’t have the option of a Peripheral Component Interconnect (PCI) slot, Personal Computer Memory Card International Association (PCMCIA) slot or USB slot, or software for WLAN connectivity).

A WGB provides a single MAC address connection into an AP and in turn then onto the Wired LAN backbone (The WGB cannot work in peer-to-peer mode). Another option is to connect a remote workgroups wired LAN. To implement a remote workgroup installation (i.e. multiple MAC addresses) the WGB is connected to a hub/switch switch with a Ethernet patch cable (for single MAC Address use a crossover cable) (NB not all implementations support this).

Ad-hoc mode

Wireless Ad Hoc Mode

Ad-Hoc Mode: This is called Independant Basic Service Set (IBSS). Mobile clients connect directly without an AP.

Peer-to-Peer (P2P) a.k.a Ad-hoc mode networking is the opposite of a Server-Client model (duh). This can be in a wired or wireless environment and is where a group of end-devices come together and form an ad-hoc/P2P network with each other to share files, pictures, music, movies and applications (The ease and current application (Kazaa and Torrents) of this type of network is the main reason the RIAA hates ad-hoc/P2P networks).

In a WLAN the coverage is very limited; where all users must be in wireless reception distance of each other. There are a couple of problems with P2P “office” networks one being that security is almost non-existent, other problems being that there is no central location for any files, applications, or printing.

In most P2P environments I have found that the receptionist is given the “server-role” Pc which creates other larger problems. The person at the front desk in a company is the receptionist, in case of a theft the first computer out the door is the server. In most cases the most “spam” is received by a receptionist (classing teddy-bears, hearts and hugs, chain-mail, friend-mail, etc. as spam) being on numerous forwarding lists increases the risk of virus, trojan, worm infection. If the company allows internet access to employees its only a matter of time before the “server” begins doing its own thing.

In a WLAN it is not a good idea (iow just don’t do it) to connect a Server, or a Server-Role computer using Wireless

Roaming

Wireless Roaming

The roaming “feature” on wireless allows a mobile user to move from one cell to another without a drop in signal or need to manually change network settings. Roaming is enabled by complete coverage with wireless cells.

Seamless roaming allows for users to move around from one cell to another.
Power management lengthens the battery life of portable devices (i.e. they don’t have to search for wireless networks all the time)
Dynamic Load Balancing distributes users among access points to increase throughput for each user.
AP with overlapping coverage cells and redundant switches provide fault tolerant WLAN networks.

A user experiences “roaming” when one of the following conditions is met:

The maximum data retry count is exceeded.
The client has missed too many beacons from the access point.
The client has reduced the data rate.
The client intends to search for a new AP at periodic intervals.

Roaming without service interruption requires identical SSIDs, VLANs and IP subnets on all APs. The client initiates the roaming when he/she searches for another AP with the same SSID and then sends a re-authentication request (for voice and video short roaming times are important).

Layer-2 and Layer-3 Roaming

Wireless Layer-2 and Layer-3 Roaming

Roaming from one AP to another AP on the same subnet (Cell 1 to Cell 2) would be considered Layer-2 roaming (data link layer). Roaming between APs that reside on different subnets (Cell 1 to Cell3) would be considered Layer-3 roaming (network layer).

Layer-2 roaming is managed by the AP, using mulicast packets that inform switches that a devices has moved. The protocol between the APs is called Inter-Access Point Protocol (IAPP).

Layer-3 roaming is managed by either Mobile IP or Lightweight Access Point Protocol (LWAPP) with a WLAN controller.

Mobile IP: allows fixed IP addresses in an IP Subnet of a network. It relies on devices like routers (home agents and foreign agents), to runel traffic for a mobile device. This was used in Legacy WLANs.

Wireless VLAN Support

Switches use VLANs to separate traffic. WLAN APs can in turn extend the VLANs by mapping VLANs to SSIDs. The VLANs then share the same wireless cell and channel end result being virtualization of the AP.

Through the use of trunking (ISL or 802.1q) the VLANs can be mapped to APs from a/the switch allowing roaming throughout the enterprise. A Cisco Aironet AP can be configured with 8 – 16 VLANs for system design flexibility. (Some client NICs require SSID broadcast, the AP can be configured for SSID broadcast per VLAN).

Wireless Enterprise (read business) Voice Architecture

Wired LAN Voice (IP Phone) networks can be extended using the 802.11e standard that specifies QoS upstream and downstram for WLAN networks. This is very important because of the delay sensitive nature of voice.

Wireless Mes Networks

A Mesh network infrastructure is decentralized and inexpensive because each node needs to transmit only as far as the next node (WirelessAfrica). The nodes act as repeaters to transmit data from nearby nodes to peers that are too far away to reach. The result is a network that can span a large area (cost effectively if each node is owned by individuals).

Mesh Networks are reliable because each node connects to several other nodes. Wireless Mesh networks differ from conventional infrastructure wireless networks in that only a subset of nodes need to be directly connected to the wired network. Extra capacity can be added by installing more nodes. Through the use of Cisco Adaptive Wireless Path Protocol (AWP(P)) each device can find a way back to wired APs and thus by extension the network. Paths (of which there are multiple) through the network can change in response traffic load, radio conditions, or traffic prioritization. The network can cover more distance by using wireless to wireless connectivity. Unlicensed bandwidth (cheap) and wireless routing allow microcells to interconnect over wireless backhaul links.

AWP Protocol

AWP allows APs to communicate with each other to determine the best path back to the wired network. After optimal path selection is estalbished, AWP continues to run as a background service to establish alternate paths to the wired network or if topology changes or other conditions causes the link streghth to diminish. (AWP runs on each AP)

AWP is a wireless protocol by design and takes into consideration wireless radio factors like interference to make a mesh network self-configuring and self-healing. Because wireless is dynamic, addition to the network causes AWP to reconfigure paths back to the wired network automatically. AWP also uses stickiness to mitigate route flaps (disconnection/temporary disruption doesnt cause mesh change).

Notes and Notices:

Network Ninja

Tag Archive for 'channels'

BCMSN Practical Lab Initial Config

Planning Voice on a Data Network

WLAN Standards

WLAN Infrastructure Topologies

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