CLEAR IIP EIGRP NEI command...does it work?

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Jun 6th, 2007
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When you run a "Sho ip eigrp nei" command it gives you the SRTT and RTO values... If your run a "clear ip eigrp nei x.x.x.x" the SRTT and RTO values recalculate and sometimes display lower values. Does clearing the eigrp neighbor actually improve network performance?

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sundar.palaniappan Wed, 06/06/2007 - 09:54
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When eigrp neighbor is cleared the SRTT or RTO values may change based on various factors like the link utilization, CPU utilization of the peer router, interface queue status and serialization etc when the routers attempt to become neighbors. There's no direct correlation between these values and network performance and it only affects how EIGRP adjacency is handled.


HTH


Sundar

cosler Wed, 06/06/2007 - 10:04
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Thanks for your input Sundar, im curious when you mention it only affects how the adjacency is handled.. could higher RTO cause the adjacency to flap? But it sounds like its more of a statistical view than anything else. Also it most cases when I clear the niehgbor the RTOP drops considerably and the people that complain of performance say they notice improvements. But you know people can say anything. lol

sundar.palaniappan Wed, 06/06/2007 - 10:11
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Definition of RTO:


Retransmission timeout (in milliseconds). This is the amount of time the software waits before resending a packet from the retransmission queue to a neighbor.


As you can see from this definition a higher RTO doesn't mean the adjacency will flap but how much time the router would wait before retransmitting a packet if a reliable packet sent by this router isn't acknowledged by the peer.


HTH


Sundar

cosler Wed, 06/06/2007 - 10:20
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Ok so in my scenario the original output for RTO was 5000ms. Once I issued the clear neighbor command it dropped down to 3000ms (which would seem to improve the waiting period). Does the command i use have any influence on the retransmit time? Better yet does the RTO metric influence the router performance or does the router performance influence the metric value displayed? NOTE: The RTO is now holding steady at 3000ms.

sundar.palaniappan Wed, 06/06/2007 - 10:24
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"Does the command i use have any influence on the retransmit time?"


Yes, it does.


"Better yet does the RTO metric influence the router performance or does the router performance influence the metric value displayed?"


If anything the router performance and other factors I stated earlier affect the calculation of RTO value and not the other way around.


HTH


Sundar

cosler Wed, 06/06/2007 - 10:30
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Thanks again Sundar. Great help indeed.

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