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Double hops on penultimate hop

  • From: "Sherwin Ang" <sherwin.ang@gmail.com>
  • Date: Mon, 13 Mar 2006 19:48:12 +0800
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  • Resent-Date: Mon, 13 Mar 2006 06:48:14 -0500
  • X-Scanned-By: MIMEDefang 2.53 on 209.239.41.31

On our MPLS network, when mpls ip propagate-ttl is enabled we don't get this double hop, but when no mpls ip propagate-ttl is enabled, we get a double hop like this
 
7600-PPE1#traceroute vrf VPN-INTERNET 66.94.230.49

Type escape sequence to abort.
Tracing the route to 66.94.230.49

  1 212.78.96.210 20 msec 16 msec 20 msec
  2 212.78.96.210 16 msec 16 msec 20 msec
  3 212.78.97.194 16 msec 20 msec 16 msec
  4 64.86.127.77 20 msec 16 msec 20 msec
  5 64.86.127.134 16 msec 20 msec 16 msec
  6 207.45.196.73 184 msec 184 msec 180 msec
  7 207.45.196.90 180 msec 184 msec 184 msec
  8 216.115.106.203 196 msec
    216.115.106.207 184 msec
    216.115.106.183 184 msec
  9 66.218.82.223 184 msec
    66.218.82.219 188 msec
    66.218.82.217 188 msec
 10 66.94.230.49 196 msec 184 msec 184 msec

with mpls ip propagate-ttl enabled

7600-PPE1#traceroute vrf VPN-INTERNET 66.94.230.49

Type escape sequence to abort.
Tracing the route to 66.94.230.49

  1 212.4.1.145 [MPLS: Labels 37/16 Exp 0] 16 msec 20 msec 16 msec
  2 212.4.1.131 [MPLS: Labels 43/16 Exp 0] 20 msec 16 msec 20 msec
  3 212.78.96.205 [MPLS: Label 16 Exp 0] 16 msec 16 msec 20 msec
  4 212.78.96.210 20 msec 16 msec 20 msec
  5 212.78.97.194 16 msec 20 msec 16 msec
  6 64.86.127.77 20 msec 16 msec 20 msec
  7 64.86.127.134 20 msec 16 msec 20 msec
  8 207.45.196.73 180 msec 184 msec 180 msec
  9 207.45.196.90 184 msec 180 msec 184 msec
 10 216.115.106.203 200 msec
    216.115.106.207 184 msec
    216.115.106.179 184 msec
 11 66.218.82.219 184 msec
    66.218.82.221 184 msec 184 msec
 12 66.94.230.49 184 msec 184 msec 200 msec

Am not sure why it's doing it, 212.78.96.210 is the point to point IP from the PE (212.78.96.209) and the CE (212.78.96.210 ) where in PE (212.78.96.209) is tagged as VPN-INTERNET and CE (212.78.96.210) is a 7606 which acts as our core router outside the MPLS network. 

Any ideas on why this is happening would be greatly appreciated.  Thanks in advance!  I've scoured through google but hasn't found anything relevant or I may have been using the wrong keywords.

Regards,

Sherwin