Cisco® CCNP Support : Tac, Cco, Catalyst Switch Commands, Vlans & Vtp.

11.0 TAC:

Two levels of access available for accessing CCO (Cisco Connection Online) are:

1. Guest access for general public. The access is limited to certain areas of CCO Website for guests.

2. Registered access for customers.

The three tools of Case management Toolkit in CCO that are accessible interact directly with TAC are:

1. Case Open - Enables you to request technical assistance by opening a case with TAC
2. Case Query - Enables you to verify the status of the case
3. Case Update - Enables you to update the case with your own information.

If a customer reports a router crash or a router hang-up to the Cisco technical support group, he may be asked to provide the outputs of the following commands:

1. Show stacks - This command displays stacks, and stack traces before the reload takes place.

2. Exception dump - The core dump is useful for obtaining a copy of memory image before router crashes. The memory image can be copied to a file by using TFTP (usually if memory dump is less than 16MB) or FTPed to a remote location. You can test the core dump by issuing the command 'write core' in privileged exec mode (enable mode). This command will cause a crash, and the content of the memory will be dumped according to the configured setup.

Cisco® has combined several important commands into one single command, for the purposes of problem reporting. The command 'show tech-support' combines several of important Cisco® commands into one single privileged command.

Cisco Technical Assistance Center (TAC) normally requires the following information when you report the case:

1. 'show running-config' command output on all routers concerned.
2. 'show version' command output on all routers concerned.
3. 'show controllers' command output on all routers concerned.
4. Details of host, servers, and network topology map
5. Network layer protocols, and version details.

12.0 SRB:

You need to configure transparent bridging or source-route bridging (SRB) to forward NetBEUI traffic to remote networks.

13.0 Cisco router encapsulation:

A Cisco router defaults to novell-ether (Ethernt_802.3). There are many encapsulation types available as given below

Common Term --- Cisco Term
Ethernet_II --- arpa
IEEE 802.3 --- sap
Novell 802.3 raw --- novell-ether
SNAP --- snap

14.0 Catalyst commands:

Some of the important Catalyst commands are:

1. Show config - This command is similar to IOS 'show running config' command.

2. Show span - This command displays information about Catalyst switched port analyzer function settings such as whether the SPAN is enabled or disabled, and whether the transmit and/or receive information is monitored. Don't confuse this with show spantree command that displays spanning tree information for a vlan.

3. Show trunk - Displays the vlan trucking information for the switch.

4. Show spantree - Displays spanning-tree information for a vlan.

5. Show spantree statistics - Displays Spanning-Tree Protocol BPDU communication in readable form.

6. Show cdp neighbors - displays CDP information about all Cisco devices connected to the switch.

Important 'show' commands for Catalyst switches that provide system settings:

1. Show system - Provides status of the system LEDs, power supplies, fan, and system among others.

2. Show test - Provides the results of diagnostic tests.

3. Show interface - Provides information on network interface flags and addressing.

4. Show module - Displays module status and information about the module.

5. Show port - A very useful command that displays information about the port and counters.

6. Show log - Displays error log.

15.0 VLANs & VTP:

A VTP capable switch can be configured as:

1. VTP server - It maintains VLAN information in a nonvolatile device or on a TFTP server.

2. Client - Clients also maintain complete list of all VLANs in the VTP domain. 

3. VTP transparent mode - Switches that do not wish to participate in VTP can be put in transparent mode. Here, VTP adverts are forwarded.

A VTP advertisement necessarily consists of "Configuration revision number". Every time a VTP server updates its VLAN information, it increments the configuration revision number by one count. VTP clients, use the revision number to enforce the VLAN configuration Update.

A non-trunk port can carry only one vlan. If more than one vlan need to be carried on a single port, trunking must be enabled on that port.

The recommended maximum hop count in a VLAN is 7, that is 7 switch/router/bridge hops are allowed in a vlan. This in other words is known as the vlan diameter. Network diameter affects the network performance while doing spanning-tree computations.
Lesser the diameter of a network, faster would be the network convergence.

The following are true about VTP:

1. Switches configured in transparent mode relay VTP adverts from other switches.

2. There must be at least 1 VTP servers in a VTP management domain.

3. It is recommended to configure VTP servers ON-LINE. This would ensure VTP domain consistency.

4. VTP does not work if there is no VLAN1 or no trunk port.

5. For CWSI (CiscoWorks for Switched Internetworks) to work, VTP is required.

A vlan belongs to a specific network number. To move traffic from one vlan (one broadcast domain) to another vlan (another broadcast domain) a router is required. 

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