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 3PING 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
10.255.10.4traceroute 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 msWhen 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 3PING 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
10.255.10.5traceroute 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