cdp over mpls

Unanswered Question
Apr 26th, 2010


we have 2 routers connected via mpls link provided by our isp

when we make sho cdp neighbor, each router cannot see the other. i understand this is normal.

is it possible to let each router sees the other one as a neighbor?

i think if we can do this, so in cw lms / topology services, we will obtain one link  between both routers. and the map will be more meaningful. isn't it?

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Overall Rating: 5 (1 ratings)
Giuseppe Larosa Mon, 04/26/2010 - 03:31

Hello Ohassairi,

the answer depends from the specific type of MPLS service that you have bought:

if it is an MPLS L3 VPN the answer is no, because each router has a peer  that is a SP router not the other router of yours

if it is a form of L2 VPN or transport, CDP could be carried over it or not depending on EoMPLS settings on SP devices.

In other words with L2 transport services it depends from SP settings, with L3 no chance to get it.

Hope to help


ohassairi Mon, 04/26/2010 - 21:44

hi guislar

it is a layer3 mpls cloud.

the solution i found is : i configured one ip gre tunnel between both routers and i added the command : cdp enable under interface tunnel 0.

the result : each router sees the opposit one in cdp neighbors and i have got the wan link drawn in network topology

Giuseppe Larosa Tue, 04/27/2010 - 00:36

Hello Ohassairi,

a very good workaround I hadn't thought about this

Hope to help



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