How will you find out Uplink in L2 switches ?

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Aug 5th, 2008

How will you find out Uplink in L2 switches

I have this problem too.
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Marwan ALshawi Tue, 08/05/2008 - 21:53

uplink is the link from access layer to distribution layer

and should be Trunk link to carry all vlan traffic

not like access port which is a port connected to end stations

also somtimes uplinks can be gorup of ports in one channel called etherchannel

in this case

group of phisical trunck port will be represented by one logical port

port-channel interface

if helpful rate

Let me give another perspective in regards to finding an uplink.

In one view the correct way is to look for some port of ether channel (port channel) or know that there is an access layer that connects to the distribution layer and look or those connections.

But, this is not always the case. There are times when a company has connected it hierarchical (misspelled) or they have daisy chained an access switch to another access switch. The easiest way is to perform a basic cdp neighbor and look at what ports are connected to the other switch. Then find out it is part of an etherchannel or not. It may be trunked (it doesnt always have to be) or if it is just an access port. (In which all the ports on the child switch will be the same vlan as the access port.) Either way, understand the architecture and find out if you have an L3 connections or is everything just l2.

In summary... the quickest and easiest way to find an uplink or any connection is "show cdp neighbor"

Ryan Carretta Wed, 08/06/2008 - 00:34

Assuming the network you are working on is totally foreign to you (no topology diagrams, CDP disabled, just inherited an existing design, etc.), the easiest way to find your active uplink port (if there's just one - as in a core/distribution/access layer topology) is going to be to find the port that is passing the most traffic, or to find the port that is passing all your vlans. 'Show interfaces' can be used for the first and 'show interfaces trunk' for the second.


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