From: Abbas Elzein (Abbas.Elzein@telus.com)
Date: Wed Aug 31 2005 - 14:04:48 GMT-3
Most likely the TTL propagation is disabled on the PEs.. Disabling TTL propagation allows the structure of the MPLS network to be hidden from customers, but not the provider.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Jerry Wang
Sent: Wednesday, August 31, 2005 12:16 PM
To: ccielab@groupstudy.com
Subject: Traceroute issue - MPLS CE router replys 2 hops on ingress & egress interfaces
Hi Guys,
Please help to explain the following traceroute issue I found in my lab:
I have 2 Routers R1 & R2 on two sites, both are connecting to MPLS/VPN cloud. When I do traceroute from R1 to R2, I found the first 2 hops reflect the ingress and egress interfaces on the same CE1 router, which is connecting to R1. Please see following details:
Traceroute path (on R1, do traceroute to R2's loopback address):
R1 -- CE1 -- PE1 -- PE2 -- CE2 -- R2
Tracing output:
1. CE1_ingress_int
2. CE1_egress_int
3. CE2_ingress_int
4. R2_ingress_int
FYI: the /30 link route between CE1 & PE1 is not advertised to R1. not sure if this affects or not.
I have no access to to the Telco CEs & PEs , I assume it might be related to CE1's MPLS traceroute configuration. Or it might be related to the ttl propagation between the IP & MPLS domain?
Your help is highly appreciated!
Thanks and best regards
Juntao
Network Engineer
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