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New Member

Twicking RIP METRICS

Hello All,

In my lab practice i was asked to manipulate the metric so that Router1 sees R2 with metric of 1 away R3 metric of 2 away and R4 of 3.I did this and was successful. Here is the output

C 1.0.0.0/8 is directly connected, Loopback0

R 2.0.0.0/8 [120/1] via 131.1.12.2, 00:00:09, Serial0/0

R 3.0.0.0/8 [120/2] via 131.1.12.2, 00:00:09, Serial0/0

4.0.0.0/24 is subnetted, 1 subnets

R 4.4.4.0 [120/3] via 131.1.12.2, 00:00:09, Serial0/0

131.1.0.0/24 is subnetted, 3 subnets

C 131.1.12.0 is directly connected, Serial0/0

R 131.1.23.0 [120/1] via 131.1.12.2, 00:00:09, Serial0/0

R 131.1.34.0 [120/2] via 131.1.12.2, 00:00:09, Serial0/0

Router1#

But problem is that i don't know why i am having something different from the "Debug ip rip" Here is teh Debug output too.

*Mar 2 07:03:52.219: RIP: sending v2 update to 224.0.0.9 via Loopback0 (1.1.1.1)

*Mar 2 07:03:52.219: RIP: build update entries

*Mar 2 07:03:52.219: 2.0.0.0/8 via 0.0.0.0, metric 2, tag 0

*Mar 2 07:03:52.219: 3.0.0.0/8 via 0.0.0.0, metric 3, tag 0

*Mar 2 07:03:52.219: 4.4.4.0/24 via 0.0.0.0, metric 4, tag 0

*Mar 2 07:03:52.219: 131.1.12.0/24 via 0.0.0.0, metric 1, tag 0

*Mar 2 07:03:52.219: 131.1.23.0/24 via 0.0.0.0, metric 2, tag 0

*Mar 2 07:03:52.219: 131.1.34.0/24 via 0.0.0.0, metric 3, tag 0

*Mar 2 07:03:52.223: RIP: ignored v2 packet from 1.1.1.1 (sourced from one of our ad

dresses)

Router1#u all

All possible debugging has been turned off

Router1#

Secondly, in the last line of the debug it says "RIP: ignored v2 packet from 1.1.1.1 (sourced from one of our ad

dresses)" Can anyone please explain what this means, even though hinder my IP reachabilities at all, yet curious to understand what it indicates since no any filtering on this router, thoug the IP ADD is a loopback or this is normal for a loopback?

Thanking you all in advance for your usual help.

Regards

3 REPLIES
Hall of Fame Super Silver

Re: Twicking RIP METRICS

Hello Netman,

let's start from the end:

*Mar 2 07:03:52.223: RIP: ignored v2 packet from 1.1.1.1 (sourced from one of our ad

dresses)

just before:

Mar 2 07:03:52.219: RIP: sending v2 update to 224.0.0.9 via Loopback0 (1.1.1.1)

this means simply that RIP process sends out a RIP update out its loop1 interface and then sees it back (for the loopback nature of the interface) and ignores it.

This is normal and just a curiosity there would be no need to send RIP updates out a loopback: it is just an implementation matter to avoid this you could add

router rip

passive interface loop1

b)

every router sends its RIP updates adding a 1 to the metrics it sees in its own routing table : it makes already the calculation for the downstream router if any (out loop1 no downstream router can be found)

Hope to help

Giuseppe

New Member

Re: Twicking RIP METRICS

Hello Giuseppe,

Many thanks for your time and clarification of updates on the loopbacks.

Though your response (b) is unclear yet, i know "every router sends its RIP updates adding a 1 to the metrics it sees in its own routing table : it makes already the calculation for the downstream router if any"

Does that mean that even if the routing table gave the required results, the metrics won't change in the debug output?.

Regards

Hall of Fame Super Silver

Re: Twicking RIP METRICS

Hello New,

I just wanted to note that outgoing RIP updates are ready to be installed by downstream routers because they are already incremented by one router hop in comparison to the metrics you see in the routing table of the local router.

I thought you had noted this and I tried to explain from what we see and from my own rememberings.

I don't know if your current scenario satisfies the specifications in this exercise: if they say the metric as seen by this router it is fine, if they say the metric as seen by other routers directly connected to this you have to reduce the offset in the offset-list (I suppose you used an offset-list on some upstream router).

This exercise helps to understand how RIP updates work.

Hope to help

Giuseppe

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