Routing

when I enable this in ingress route,it is fine when I run tracroute from outside,it see the whole lsp as one single hop

but when I run traceroute in this ingress route,something interesting happens ,I saw 2 same egress ip display in the screen

why?

I only found this in  juniper site:When you use traceroute to diagnose problems with an LSP from outside that LSP, traceroute sees the ingress router, although the egress router performs the TTL decrement. The behavior of traceroute is different if it is initiated from the ingress router of the LSP. In this case, the egress router would be the first router to respond to traceroute.

http://www.juniper.net/techpubs/en_US/junos11.3/topics/reference/configuration-statement/no-decrement-ttl-edit-protocols-mpls.html?searchid=1354104137128

but it doesn't tell me why there 2 same egress ip displayed in screen when running traceroute

Hi Rob,

Ideally this shouldn't be the case. Can you please provide me your topology and the configs?

Regards

Surya

what is the expected behavior in ingress router and in other router outside of the lsp?

Hi Rob,

Both ingress and the outside router should see it as a single hop for LSP path i.e. both traceroute output should show only one LER address.

+---+ .1              .2 +----+ .1          .2 +----+.1          .2 +----+.1           .2 +---+

| A |--------------------| R1 |----------------| R2 |---------------| R3 |----------------| B |

+---+   172.168.1.0/30   +----+   10.8.1.0/30  +----+  20.8.1.0/30  +----+   58.8.1.0/30  +---+

                       |<----------------LSP--------------->|

Traceroute from A towards B should have:

     [1] R1 interface address                     [172.68.1.2]

     [2] R3 interface address towards R2          [20.8.1.2]

     [3] B destination address                    [58.8.1.2]

Traceroute from R1 towards B should have:

     [1] R3 interface address towards R2          [20.8.1.2]

     [2] B destination address                    [58.8.1.2]

Regards

Surya