Ethernet Switches & Routers

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Occasional Contributor
Posts: 8
Registered: ‎11-21-2016
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Traceroute not working between CE to CE in MPLS network

[ Edited ]

Hello, hoping someone can offer some guidance.

 

I've implemented MPLS LDP across our core network, with the objective of providing MPLS VPN services to our customers.

 

The issue is that when I run a traceroute between the CE's, the output does not show the PE routers or any labels. It simply displays * * * after the first hop. However, I have end to end connectivity proven by ping tests.

 

----------------------------------------------------------------------------

 

CE1#traceroute 192.168.6.1 source 192.168.2.1
Type escape sequence to abort.
Tracing the route to 192.168.4.1
VRF info: (vrf in name/id, vrf out name/id)
1 10.0.0.1 [AS 65123] 20 msec
   10.0.0.2 [AS 65123] 12 msec
   10.0.0.1 [AS 65123] 12 msec
2 * * *
3 * * *

 

 

CE1#ping 192.168.6.1 source 192.168.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.6.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.2.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/16/20 ms

 

----------------------------------------------------------------------------

 

- I've attached a network diagram for reference.

 

NOTE:

  1. CE's run BGP and use multipath, so both CE's load balance between the two PE's.
  2. CE's are Cisco routers
  3. PE's are Brocade CER series routers
  4. I simulated the exact network scenario in GNS3 using Cisco IOS and can see MPLS labels in the traceroute output from one CE to another. 

 

 

----CONFIG ON PE4----

 

ip icmp mpls-response use-lsp
!
router isis
 net 00.748e.f8a9.29c1.00
  address-family ipv4 unicast
  exit-address-family

!
interface loopback 1
 port-name MPLS-LDP
 ip router isis
 ip address 192.168.217.2/32
!
interface ethernet 1/2
 port-name MPLS-Backhaul
 enable
 ip router isis
 ip address 192.168.216.2/28
!
router mpls
 ldp
 lsr-id 192.168.217.2

 

   mpls-interface e1/2
    ldp-enable
exit
!
router bgp
 local-as 65123
 neighbor 192.168.217.1 remote-as 65123
 neighbor 192.168.217.1 update-source loopback 1
 neighbor 192.168.217.2 remote-as 65123
 neighbor 192.168.217.2 update-source loopback 1
 neighbor 192.168.217.4 remote-as 65123
 neighbor 192.168.217.4 update-source loopback 1

 

address-family vpnv4 unicast
 neighbor 192.168.217.1 activate
 neighbor 192.168.217.1 send-community both
 neighbor 192.168.217.2 activate
 neighbor 192.168.217.2 send-community both
 neighbor 192.168.217.4 activate
 neighbor 192.168.217.4 send-community both
exit-address-family

 

 

 ---MPLS LDP VERIFICATION---

 

 

PE#show mpls ldp interface
Total number of LDP interfaces : 1
               Label-space   Nbr       Hello        Next
Interface ID                   Count   Interval    Hello
e1/2        0                     3          5              4 sec

PE#show mpls ldp peer brief
Number of LDP peers: 3
Number of LDP peers with operational session: 3

 

Peer LDP ID       State
192.168.217.1:0 Operational
192.168.217.2:0 Operational
192.168.217.4:0 Operational

PE#show mpls forwarding
R: RSVP, L: LDP, S: Static
Total number of MPLS forwarding entries: 6


    Dest-prefix                 In-lbl   Out-lbl  Out-intf  Sig  Next-hop            Type
1  192.168.217.1/32       -         3           e1/2       L     192.168.216.1     -
2                                     2048  3           e1/2       L     192.168.216.1    -
3  192.168.217.4/32       -         3           e1/2       L     192.168.216.4    -
4                                     2049  3           e1/2       L     192.168.216.4    -
5  192.168.217.2/32       -         3           e1/2       L     192.168.216.2    -
6                                     2050  3           e1/2       L     192.168.216.2    -

Occasional Contributor
Posts: 8
Registered: ‎11-21-2016

Re: Traceroute not working between CE to CE in MPLS network

UPDATE

 

I had 'ip unreachables' disabled on the external/WAN interface on the CE, which prevented traceroute from displaying all the hops.

 

After enabling 'ip unreachables' on the external interface, traceroute displayed correct results.

 

 

 

 

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