Cdp discovery uplink


if have someway that i can know what is the uplink of cisco switch , with use cdp?

the case is that switch are connect with two other cisco switch , both one of then are uplink, have some way to know what is the uplink, ? and the downlink?

thank you

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if the devices are running cdp and letting those links participate in CDP



DiGiTAL_ViNYL (no email)

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hi marcelo,

if i understand u right, u have two cisco switches connected to each other over two links. Now u want to know which link is active.

well... it depends on your configuration. do u use Trunking or Etherchannel? if not just issue the command "sh cdp neigh" and u will see whitch ports are used for connectivity. With a "sh spanning-tree" it will tell u which Port is blocking and which is forwarding.

regards Sebastian

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hi sebastion,

both are link active, i will ppaint for the my problem

all network device are cisco

www --- A----B----C

A are cisco router that connect my network to world (www) B and C are cisco switch that computer are linked B are linked to A and C

the uplink of B is A , and the uplink of C are B

when i ask the cdp neigh from B , i recevied that C and A are connect to this switch.

so if have some way with cdp , that i can know that A are the uplink of B?

thank you



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UPLINK has no one, specific meaning in networks. It is mostly a human term. We view "UP" as a variety of things, usually UP towards the internet, or UP towards our router, or UP towards our server, or up towards our central office. Each definition changes UP to point somewhere else. If you are speaking about SPanning Tree your uplink points towards the spanning Tree root, which has nothing to do with routers or Internet. The links are bidirectional and there is no UPLINK and DOWNLINK.

A is connected to B B is connected to C

That is all.

A packet from C must go to B then go to A. CDP only shows immediate/connected neighbors. C does not know where A is. It only knows how to get to a MAC address which B claims to know about, so it hands it to B. B then hands it to A.

DiGiTAL_ViNYL (no email)

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