Routing Loop Traceroute

akhran1974 · ‎11-29-2007

Routing table of Router 1:

R1#sh ip rou

Gateway of last resort is not set

200.200.200.0/32 is subnetted, 1 subnets

S 200.200.200.200 is directly connected, FastEthernet0/0

100.0.0.0/32 is subnetted, 1 subnets

S 100.100.100.100 [1/0] via 10.1.1.1

10.0.0.0/24 is subnetted, 3 subnets

O 10.3.3.0 [110/2] via 10.1.1.1, 07:09:30, FastEthernet0/0

O 10.2.2.0 [110/2] via 10.1.1.1, 07:09:30, FastEthernet0/0

C 10.1.1.0 is directly connected, FastEthernet0/0

150.150.0.0/32 is subnetted, 1 subnets

S 150.150.150.150 [1/0] via 10.3.3.2

Routing table of Router 2:

R2#sh ip route

Gateway of last resort is not set

200.200.200.0/32 is subnetted, 1 subnets

O E2 200.200.200.200 [110/20] via 10.1.1.2, 00:37:51, FastEthernet1/0

10.0.0.0/24 is subnetted, 3 subnets

C 10.3.3.0 is directly connected, FastEthernet1/1

C 10.2.2.0 is directly connected, FastEthernet1/2

C 10.1.1.0 is directly connected, FastEthernet1/0

150.150.0.0/32 is subnetted, 1 subnets

O E2 150.150.150.150 [110/20] via 10.1.1.2, 00:29:42, FastEthernet1/0

When I do a traceroute to 150.150.150.150 on Router 1, I have:

R1(config)#do traceroute 150.150.150.150

Type escape sequence to abort.

Tracing the route to 150.150.150.150

1 10.1.1.1 48 msec 60 msec 12 msec

2 10.1.1.2 52 msec 48 msec 32 msec

3 * * *

4 * * *

5 * * *

Shouldn't the traceroute be :

R1(config)#do traceroute 150.150.150.150

Type escape sequence to abort.

Tracing the route to 150.150.150.150

1 10.1.1.1 48 msec 60 msec 12 msec

2 10.1.1.2 52 msec 48 msec 32 msec

3 10.1.1.1 48 msec 60 msec 12 msec

4 10.1.1.2 52 msec 48 msec 32 msec

5 10.1.1.1 48 msec 60 msec 12 msec

6 10.1.1.2 52 msec 48 msec 32 msec

Thanks !

vinoth_g · ‎11-29-2007

Traceroute works this way...First time it sets the ttl vlaue 1 and send to the destination ..first hop router (in your case R2) replies with time exceded message..Second time it sets the ttl vlaue to 2 and send it to the destination...Second hop router (R1) will reply with time exceeded message...the third time it sets the ttl vlaue 3 and send it..tht packet will be in loop...it will display the ip of the router which sends time exceded message. For the third and rest of the pkts will be in loop and no one will reply with time exceeded message within specified time..

Thx