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Pinging the CE Router from Another CE Router

The following sections describe how to use the ping and traceroute commands to troubleshoot Layer 3 VPN topologies. You can ping one CE router from the other by specifying the other CE router’s loopback address as the IP address in the ping command. This ping command succeeds if the loopback addresses have been announced by the CE routers to their directly connected PE routers. The success of these ping commands also means that Router CE1 can ping any network devices beyond Router CE2, and vice versa. Troubleshooting Layer 3 VPNs Using ping and traceroute shows the topology referenced in the following examples:

Pinging Router CE2 from Router CE1

Ping Router CE2 (VPN5) from Router CE1 (VPN4):


user@vpn4> ping 10.255.10.5 local 10.255.10.4 count 3
PING 10.255.10.5 (10.255.10.5): 56 data bytes
64 bytes from 10.255.10.5: icmp_seq=0 ttl=253 time=1.086 ms
64 bytes from 10.255.10.5: icmp_seq=1 ttl=253 time=0.998 ms
64 bytes from 10.255.10.5: icmp_seq=2 ttl=253 time=1.140 ms
--- 10.255.10.5 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.998/1.075/1.140/0.059 ms

Using traceroute from Loopback to Loopback

To determine the path from Router CE1’s loopback interface to Router CE2’s loopback interface, use the traceroute command:


user@vpn4> traceroute 10.255.10.5 source 10.255.10.4
traceroute to 10.255.10.5 (10.255.10.5) from 10.255.10.4, 30 hops max, 40 byte packets
 1  vpn1-fe-110.isp-core.net (192.168.192.1)  0.680 ms  0.491 ms  0.456 ms
 2  vpn2-t3-001.isp-core.net (192.168.192.110)  0.857 ms  0.766 ms  0.754 ms
     MPLS Label=100005 CoS=0 TTL=1 S=1
 3  vpn5.isp-core.net (10.255.10.5)  0.825 ms  0.886 ms  0.732 ms

When you use the traceroute command to examine the path used by a Layer 3 VPN, the provider (P) routers in the service provider’s network are not displayed. As shown above, the jump from Router VPN1 to Router VPN2 is displayed as a single hop. The P router (VPN3) shown in Troubleshooting Layer 3 VPNs Using ping and traceroute is not displayed.

Pinging Router CE1 from Router CE2

Ping Router CE1 (VPN4) from Router CE2 (VPN5):


user@vpn5> ping 10.255.10.4 local 10.255.10.5 count 3
PING 10.255.10.4 (10.255.10.4): 56 data bytes
64 bytes from 10.255.10.4: icmp_seq=0 ttl=253 time=1.042 ms
64 bytes from 10.255.10.4: icmp_seq=1 ttl=253 time=0.998 ms
64 bytes from 10.255.10.4: icmp_seq=2 ttl=253 time=0.954 ms
--- 10.255.10.4 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.954/0.998/1.042/0.036 ms

Using traceroute from Router CE2 to Router CE1

To determine the path from Router CE2 to Router CE1, use the traceroute command:


user@vpn5> traceroute 10.255.10.4 source 10.255.10.5
traceroute to 10.255.10.4 (10.255.10.4) from 10.255.10.5, 30 hops max, 40 byte packets
 1  vpn-08-t3-003.isp-core.net (192.168.193.2)  0.686 ms  0.519 ms  0.548 ms
 2  vpn1-so-100.isp-core.net (192.168.192.100)  0.918 ms  0.869 ms  0.859 ms
     MPLS Label=100021 CoS=0 TTL=1 S=1
 3  vpn4.isp-core.net (10.255.10.4)  0.878 ms  0.760 ms  0.739 ms

Published: 2010-04-27

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