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ISIS traffic-eng mpls used, forwarding-table empty

davehouser1
Beginner
Beginner

I wanted implement label distribution without LDP. To accomplish this I planned to use a dynamic routing protocol capable of distributing the labels (ISIS or eBGP). 
I set up a ISIS network and was able to configure mpls traffic-engineering tunnels and distribute using ISIS. I followed this guide to accomplish this. Note all configurations are done in Cisco IOS v15, via IOU virtual routers in GNS3 2.22.

I think labels are being distributed properly but I am not sure. 
I usually run the command `show mpls forwarding-table` when using LDP, but this table is empty when using mpls traffic-eng. 

Looking at traffic on the interfaces between routers, no LDP traffic is being sent, only ISIS HELLO, CSNP, and RSVP traffic (The actual protocol transmitting labels I believe) 

 

Two questions:
- Why is the mpls forwarding-table empty? (Is it just a command for LDP implementations)?
- What command can I run in IOS to see how labels are popped, swapped, or added like I can see in `show mpls forwarding-table`?

2 REPLIES 2

Georg Pauwen
VIP Master VIP Master
VIP Master

Hello,

 

can you post the GNS3 project file and the configs ?

Giuseppe Larosa
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

Hello @davehouser1 ,

when you use MPLS traffic engineering externsions to IS-IS label distribution and binding are performed by RSVP TE protocol not by ISIS.

And yes the show commands are different.

 

It is totally different from LDP automatic label distributions with RSVP TE and an IGP with TE extensions you need to manually configure MPLS TE tunnels with a destination that is the loopback address of the remote PE.

AS LDP LSP paths RSVP TE tunnels are unidirectional with a tail end node ( the source) and an head end node ( the destination).

 

Multiple MPLS TE tunnels can exist between the same pair of PE  nodes per direction.  You ca use them in different ways .. What is important to note is that MPLS TE tunnels are not obliged to follow the shorted path between source PE nad destination PE and they can use alternate paths .

The typical usage is to move some traffic flows away from best path to avoid congestion ot to take advantage of MPLS fast re-route function .

 

Hope to help

Giuseppe

 

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