Psy4HA
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Cisco Traceroute returning unexpected IP source
Hi i just wanted to clear up some confusion. I have the following setup in GNS3:
Loopback interface off of R4 has two paths to loop back interface on router 1. Source 5.5.5.1 destination 65.0.0.1.
When i setup a traceroute with ONE probe count to 65.0.0.1 from interface lo1 on R4 it returns the following:
1 4.4.4.1 28 msec
2 1.1.1.1 52 msec
I understand why 4.4.4.1 would be returned but not sure why 1.1.1.1 is returned for the following hop? I would expect 2.2.2.1? Is R1 load balancing in reverse? I tried changing bandwidth on fa0/0 and fa0/1 on R1 so that fa0/1 is preferred.
Also when i issue the command where it sends 3 probes instead of one i get the following:
1 4.4.4.1 28 msec
3.3.3.1 28 msec
4.4.4.1 20 msec
2 1.1.1.1 48 msec
2.2.2.1 48 msec
1.1.1.1 36 msec
I believe traceroute is sending out multiple icmp ping paths due to multiple route paths in FIB. I am pretty sure that in the following 1a is the first hop and 2a is the second hop? Then 1b was second alternative path first hop and 2b is the second alternate path second hop? But again they return the opposite of what i would expect in both cases on the second hop?
1 a.4.4.4.1 28 msec
b. 3.3.3.1 28 msec
c. 4.4.4.1 20 msec
2 a. 1.1.1.1 48 msec
b. 2.2.2.1 48 msec
c. 1.1.1.1 36 msec
Thank you!
Cory
Loopback interface off of R4 has two paths to loop back interface on router 1. Source 5.5.5.1 destination 65.0.0.1.
When i setup a traceroute with ONE probe count to 65.0.0.1 from interface lo1 on R4 it returns the following:
1 4.4.4.1 28 msec
2 1.1.1.1 52 msec
I understand why 4.4.4.1 would be returned but not sure why 1.1.1.1 is returned for the following hop? I would expect 2.2.2.1? Is R1 load balancing in reverse? I tried changing bandwidth on fa0/0 and fa0/1 on R1 so that fa0/1 is preferred.
Also when i issue the command where it sends 3 probes instead of one i get the following:
1 4.4.4.1 28 msec
3.3.3.1 28 msec
4.4.4.1 20 msec
2 1.1.1.1 48 msec
2.2.2.1 48 msec
1.1.1.1 36 msec
I believe traceroute is sending out multiple icmp ping paths due to multiple route paths in FIB. I am pretty sure that in the following 1a is the first hop and 2a is the second hop? Then 1b was second alternative path first hop and 2b is the second alternate path second hop? But again they return the opposite of what i would expect in both cases on the second hop?
1 a.4.4.4.1 28 msec
b. 3.3.3.1 28 msec
c. 4.4.4.1 20 msec
2 a. 1.1.1.1 48 msec
b. 2.2.2.1 48 msec
c. 1.1.1.1 36 msec
Thank you!
Cory
Do you have multiple default routes in any of the routers?
ASKER
None of the routers have any manual routes set. All using eigrp.
ASKER
here's r4 route table:
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/307200] via 3.3.3.1, 00:28:37, FastEthernet0/1
2.0.0.0/24 is subnetted, 1 subnets
D 2.2.2.0 [90/307200] via 4.4.4.1, 00:32:39, FastEthernet0/0
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, FastEthernet0/1
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, FastEthernet0/0
65.0.0.0/24 is subnetted, 1 subnets
D 65.0.0.0 [90/435200] via 4.4.4.1, 00:32:39, FastEthernet0/0
[90/435200] via 3.3.3.1, 00:32:41, FastEthernet0/1
5.0.0.0/24 is subnetted, 1 subnets
C 5.5.5.0 is directly connected, Loopback1
AND R1:
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, FastEthernet0/1
3.0.0.0/24 is subnetted, 1 subnets
D 3.3.3.0 [90/307200] via 1.1.1.2, 00:28:55, FastEthernet0/0
4.0.0.0/24 is subnetted, 1 subnets
D 4.4.4.0 [90/307200] via 2.2.2.2, 00:28:55, FastEthernet0/1
65.0.0.0/24 is subnetted, 1 subnets
C 65.0.0.0 is directly connected, Loopback1
5.0.0.0/24 is subnetted, 1 subnets
D 5.5.5.0 [90/435200] via 2.2.2.2, 00:28:56, FastEthernet0/1
[90/435200] via 1.1.1.2, 00:28:56, FastEthernet0/0
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/307200] via 3.3.3.1, 00:28:37, FastEthernet0/1
2.0.0.0/24 is subnetted, 1 subnets
D 2.2.2.0 [90/307200] via 4.4.4.1, 00:32:39, FastEthernet0/0
3.0.0.0/24 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, FastEthernet0/1
4.0.0.0/24 is subnetted, 1 subnets
C 4.4.4.0 is directly connected, FastEthernet0/0
65.0.0.0/24 is subnetted, 1 subnets
D 65.0.0.0 [90/435200] via 4.4.4.1, 00:32:39, FastEthernet0/0
[90/435200] via 3.3.3.1, 00:32:41, FastEthernet0/1
5.0.0.0/24 is subnetted, 1 subnets
C 5.5.5.0 is directly connected, Loopback1
AND R1:
Gateway of last resort is not set
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
2.0.0.0/24 is subnetted, 1 subnets
C 2.2.2.0 is directly connected, FastEthernet0/1
3.0.0.0/24 is subnetted, 1 subnets
D 3.3.3.0 [90/307200] via 1.1.1.2, 00:28:55, FastEthernet0/0
4.0.0.0/24 is subnetted, 1 subnets
D 4.4.4.0 [90/307200] via 2.2.2.2, 00:28:55, FastEthernet0/1
65.0.0.0/24 is subnetted, 1 subnets
C 65.0.0.0 is directly connected, Loopback1
5.0.0.0/24 is subnetted, 1 subnets
D 5.5.5.0 [90/435200] via 2.2.2.2, 00:28:56, FastEthernet0/1
[90/435200] via 1.1.1.2, 00:28:56, FastEthernet0/0
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Article answers the question.
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in this example i pinged from 65.0.0.1 to 5.5.5.1 and got:
1 2.2.2.2 24 msec
2 3.3.3.2 48 msec
here is debug packet from r4:
*Mar 1 01:19:12.823: IP: s=2.2.2.1 (FastEthernet0/1), d=5.5.5.1, len 28, rcvd 0
*Mar 1 01:19:12.827: UDP src=49232, dst=33435
*Mar 1 01:19:12.827: IP: tableid=0, s=3.3.3.2 (local), d=2.2.2.1 (FastEthernet0/0), routed via FIB
*Mar 1 01:19:12.831: IP: s=3.3.3.2 (local), d=2.2.2.1 (FastEthernet0/0), len 56, sending
*Mar 1 01:19:12.839: ICMP type=3, code=3