How will you find out Uplink in L2 switches ?

[vinothlb1]

How will you find out Uplink in L2 switches

[Marwan ALshawi]

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

[vinothlb1]

tell me command to find Uplink

[Marwan ALshawi]

show ip uplink

[noisey_uk]

Bahahaha! Good call. OP - you need to learn some manners.

[ericngimme]

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]

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.

[sklemt4cisco]

Hi vino,

As ericngimme said
easiest way to find an uplink or any connection is "show cdp neighbor"

or with "show lldp neighbors"

as Ryan Carretta points out,
if CDP disabled i.e. "multivendor"

then you'll be using the lldp protocol:

"show lldp neighbors"

and look for the ports to see if they are bundled together as
port-channel, etherchannel and look at which ports have the most traffic.

"show port-channel summary"

then look at those individual interfaces and their "packets per second" thruput

"show interface Eth1/49 | include pps"

HTH, Scott

[Joseph W. Doherty]

To my knowledge, there's no single command that will identify the "uplink" (which, BTW, there might be more than one of).

It's been suggested that the link with the most traffic would be the uplink, and that's often likely true, but a pair of hosts could be passing the bulk of traffic, while not using an uplink, so it's not a guarantee.

What would be a better clue might be which link is carrying the most different IPs, for the "far side" of the link.  Unfortunately, a L2 switch might not be able to reveal such stats because it's interested in L2 addresses, not L3 addresses.

A network topology mapping program might reveal a network's topology so you can "see" what would be an uplink, but such programs don't always successfully reveal a network's actual topology.  The latter, is why, often in-place, personal examination of network device connections is needed to answer questions such as yours.  (Also why, I've also seen, manual maintenance of network diagrams - kept in sync with physical changes to the network.)