Saturday, September 11, 2010

Troubleshooting and Optimizing Switches

By Default every port on Cisco switch is set to auto

In case of a conflict such as one side is full duplex and one side is half duplex collision can occur and network will slow down or may not work

In that case entering the interface duplex and speed should be set manually

For example

int fa 0/0
ip address
duplex auto

duplex half

duplex full

Then Type

speed 10


speed 100

speed auto

To stop being interrupted by constant messages the command logging synchronous

For example

line console 0
logging synchronous


line vty 0 4
logging synchronous

To stop getting logout from console or virtual teletype(vty) session


exec-timeout 180 0(180 minutes and 0 seconds)


If you never want to get logged out


no exec-timeout

To stop name to ip translation(this can be really annoying)

From global config mode


no ip domain-lookup

To create a short cut for a very useful command by creating alias

For example to create a shortcut of the command sh ip int brief

Type from global config mode

alias exec s sh ip int brief

Then type

do s

This will perform sh ip int brief command

Concept of STP(spanning tree protocol)

If two cisco devices connected in multiple connections the broadcast storm creates a loop and seriously damage the network operation but redundant connections are sometimes really needed

Spanning tree protocols are basically blocks the redundant link from broadcast storm and constantly watches the active link,whenever the active link dies it lets the broadcast storm flow through the redundant link maintaining the connectivity

To get detailed information about an interface


sh interfaces fa 0/1

To see the interfaces descriptively


sh interfaces description

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