EIGRP RTO Value

Unanswered Question
Feb 22nd, 2007

What is the RTO value on show ip eigrp neighbor?

I have two wan link with same bandwidth. The RTO value for one link is 10 times higher than the other. Is it abnormal?

Thanks.

I have this problem too.
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purohit_810 Thu, 02/22/2007 - 20:37

Is it like that... One is Ethernet interface and another one is Fastethernet...

2) Both links are Leased line and point-to-point?

Because it should not happen.

3) If it is Hub and spoke environment than it couls be possible. Beacause... in the way.. how much traffice is there.. it works on it.

Regards,

Dharmesh Purohit

ruwhite Fri, 02/23/2007 - 12:52

Yes... RTO is an instantaneous measurement, taken only when a reliable packet needs to be sent measuring the time between when the packet was sent and when an ack for that packet was received. This includes time in the various queues, serialization, delay across the link, time in various inbound queues, processing time at the remote router, and all the queues, serialization, and stuff, on the way back. So, this doesn't measure delay through the link, or anything like that.

It's also measured across a relatively small number of packets, just reliable EIGRP packets sent to the single peer. Results can vary widely depending on how many reliable packets have been exchanged between two routers, the processor state on both routers, queue state on both routers, link state at that moment, etc.

It's not at all unusual for two routers to have dramatically different across the same link, or for two neighbors peered with each other over two links to have dramatically different RTO's. The SRTT should, probably, be closer, but there's no guarantee of this, either.

The RTO and SRTT are not used in the metrics in any way, and hence don't impact load sharing. The only thing they impact is the amount of time a router will wait before retransmitting a packet which has not been acknowledged.

HTH.

:-)

Russ

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