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Question on EIGRP route (traceroute weird)

Posted on 2010-11-30
5
560 Views
Last Modified: 2012-05-10
R1 has two paths to get to 172.16.1.1
via 2.2.2.1 and via 3.3.3.1

Why does the trace look like this?:

1  2.2.2.1  4 msec
   3.3.3.1   4 msec
   2.2.2.1 0 msec

2  1.1.1.1  4msec
   4.4.4.2  4msec
   1.1.1.1  4 msec na
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Question by:orus
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5 Comments
 
LVL 17

Expert Comment

by:rochey2009
ID: 34241916
Hi,

It's alternating each probe over both paths.
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Author Comment

by:orus
ID: 34241969
is this normal behavior?
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LVL 17

Expert Comment

by:rochey2009
ID: 34242051
yes the per packet load balancing is normal for equal cost routes (and with some configuration using the EIGRP variance command for unequal cost routes). However in your case both the paths are not really equal since the path to 172.16.1.1 through R3 is an extra hop but this is a consequence of redistribution between protocols and can sometimes introduce suboptimal routes such as the one through R3.

I think you can change the per packet loadbalancing behaviour.
0
 

Author Comment

by:orus
ID: 34242176
final question. What is the actual path between R1 and 172.16.1.1 (r4)
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LVL 17

Accepted Solution

by:
rochey2009 earned 500 total points
ID: 34242291
There are two paths

One of them goes from R1 to R2 via the 2.2.2.0 subnet and then onto R4 via the 4.4.4.0 subnet

The other goes from R1 to R3 via the 3.3.3.0 subnet, crosses the 1.1.1.0 subnet to R2 and then onto R4 via the 4.4.4.0 subnet. So this route is suboptimal due to the redistribution.
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