Hello,
I work with an MPLS service provider, we have this weird this with our Cisco routers, when the client does a traceroute from their Site-A to Site-B and also do the opposite, they get difference results, always missing 2 hops. The client thinks there is a routing issue but in fact it's not, the traffic is going through but why certain hops are not displayed ?
More details here:
Traceroute from Site A core switch to Site B core switch "10.10.20.1" that is connected to internal LAN (missing 2 hops, which are PE next to CE-Site-B and CE-Site-B WAN IP), this is weid because usually when a router doesn't respond to ICMP request the sender router is supposed to display Asterisk ( ************) that means no response.
CoreSW-Site-A#traceroute 10.10.20.1
Type escape sequence to abort.
Tracing the route to 10.10.20.1
1 172.16.9.5 0 msec 0 msec 0 msec <===== CE-Site-A LAN interface
2 172.31.122.189 4 msec 4 msec 0 msec <==== PE next to CE-Site-A
3 172.16.254.1 4 msec * 0 msec <=====Client equipment connected to CE-Site-B LAN interface
Traceroute from Site B core switch to Site A core switch "10.11.1.1" that is connected to internal LAN (this is correct, it shows all 5 hops)
CoreSW-CE-Site-B#trace 10.11.1.1
Type escape sequence to abort.
Tracing the route to 10.11.1.1
1 172.16.254.2 0 msec 4 msec 0 msec <====== CE-Site-B LAN interface "ASR-920"
2 172.31.122.237 0 msec 0 msec 4 msec <======PE next to CE-Site-B "ASR-903"
3 172.31.122.189 0 msec 4 msec 4 msec <======PE next to CE-Site-A
4 172.31.122.190 4 msec 4 msec 0 msec <======== CE-Site-A WAN interface
5 172.16.9.2 4 msec * 0 msec <====== Client equipment connected to CE-Site-A LAN interface
Two other tests done directly from our CEs:
Traceroute from CE-Site-A LAN interface to CE-Site-B LAN interface (Shows only 2 hops, missing PE next to Site-B router "172.31.122.237"
CE-Site-A#trace 172.16.254.2 source g0/0/1
Type escape sequence to abort.
Tracing the route to 172.16.254.2
VRF info: (vrf in name/id, vrf out name/id)
1 172.31.122.189 2 msec 3 msec 2 msec <===== PE next to Site-A router
2 172.31.122.238 [AS 22652] 5 msec * 7 msec <======= CE-Site-A WAN interface
Traceroute from CE-Site-B router LAN interface to CE-Site-A LAN interface ( Shows 3 hops which is correct )
CE-Site-B#trace 172.16.9.5 source te0/0/3
Type escape sequence to abort.
Tracing the route to 172.16.9.5
VRF info: (vrf in name/id, vrf out name/id)
1 172.31.122.237 4 msec 0 msec 4 msec <====PE next to CE-Site-B
2 172.31.122.189 [AS 22652] 24 msec 4 msec 4 msec <==== PE next to CE-Site-A
3 172.31.122.190 [AS 22652] 4 msec * 4 msec <==== CE-Site-A WAN interface
Please note that there is no ACL neither on CEs or PEs, Any idea why this behaviour is happening ?
Thank you,
Amine
