LDP cause client can not login

Unanswered Question
Nov 6th, 2008

I have a network ,which use two 12012 as core and there are two 7609s separably connect to them.These two 7609s separably connect to two 6509 by trunk.On these 6509s,there are only Layer 2 configuration and a vlan with address used to admin this switch.Some server connect to the 6509s.

There are two other 7609s separably connected to 12012,too.A lot of clients connect to them.

Now I want to config LDP between 12012 and 7609 ,which connect to 6509.After I configed LDP on them,my client can not login server from 7:00 a.m to 9:00 a.m (In this range of time,the amount of clients who wants to login increase quickly).In other conditions,my clients login server normally.


I have this problem too.
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csco10716389 Thu, 11/06/2008 - 22:32

U must be using the trunk port for LDP as well as Vlan traffic,if it is this then please take use of logical interfaces and seperate the traffic.PLease use the LDP on any one logical interface for MPLS.

Giuseppe Larosa Fri, 11/07/2008 - 04:53

Hello Ding,

a typical problem when introducing MPLS in a network:

this is an MTU problem:

an IP packet inside an MPLS frame has an overhead of 4 byte for each MPLS label.

you need to increase the MTU on all trunk links to be able to pass packets with IP size 1500 byte.

Hope to help


csco10716389 Sat, 11/08/2008 - 04:14

PLease take help using loopback interface for Enabling LDP and let the trunkport over the phisical interface.please don't forget to put route for acknowledge loopback interface for communication.


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