Traffic Engineering Tunnels

Unanswered Question
Oct 31st, 2008

I have few questions regarding TE tunnels. Would appreciate your help in understanding some concepts:

1. Why do you use a traffic engineering tunnels? Is this to force traffic to take a particular path? What is the real advantage?

2. What is the effect of routing protocol in choosing path for TE tunnels? I beleive when you define TE tunnel you give path cost? So what is the effect of IGP/OSPF path cost in this case?

3. Does TE tunnel has anything to do with GRE tunnels? Can you define TE tunnel destination to be a remote address like the way in GRE in tunnels?


I have this problem too.
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Harold Ritter Fri, 10/31/2008 - 11:26


1. There is multiple reasons why one would want to use MPLS TE. One reason can be to select a path through the network that would not necessarily be selected by the IGP, which leads to a better resource utilization. A second reason could be that using MPLS TE allows you to also use MPLS TE Fast ReRoute (FRR), which will cause traffic to converge in a few milliseconds upon link or node failure.

2. By default, the cost from the tunnel head-end an tail-end routers will be the best IGP cost between these two nodes.

3. MPLS TE tunnels and GRE tunnel are both tunnel interface but they have very little in common, apart from the configuration CLI. That being said, you still need to configure a destination address with the TE tunnel as you do GRE tunnel.


fawad.alam Fri, 10/31/2008 - 12:24

Thanks for the nice post, Harold!!

Few comments and some more questions.

1. DO you mean MPLS TE allows for manual traffic flow control? Does it allow you to configure redunancy and load sharing by using mpls traffic engineering "priority", "bandwidth" and "affinity" command options?

2. DO you need to configure Traffic Enginnering on both PE and P throughout the MPLS network?

3. Can TE tunnel destination IP address be an IP address on a remote PE or P router?

Thanks mch!


Giuseppe Larosa Fri, 10/31/2008 - 13:05

Hello Fawad,

1) yes: you can decide to announce in the IGP or not announce in the IGRP the MPLS TE tunnel and to use it to move some traffic quotas for example to reduce congestion on the shortest path. (without autoroute announce you can use the tunnel by specifying it as the outgoing interface in a static route )

2 )

Yes, because MPLS TE uses an extended version of RSVP: RSVP TE and it is RSVP TE the protocol that negotiate the tunnel setup.

So on each router you need:

to enable the TE extensions of the link state protocol OSPF or IS-IS (no other option)

to choice a loopback as the MPLS TE Router-ID that will represent the node in the MPLS TE topology (advertised in OSPF or IS-IS)

You need to enable mpls traffic-engineering in global config and on the every link you enable mpls traffic-engineering and you assign an RSVP bandwidth resource that will be used to setup tunnels (used also on the routers in the middle and oubound only)


the MLS TE tunnel should have as destination the MPLS TE Router-ID of the remote PE: a continous path within the MPLS domain with enough resources on each link has to be found for successful setup

Hope to help



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