I like to do labs to verify things (it helps me remember more than just
reading or being told the answer) so I decided to lab up your question. I
tossed in a sniffer to look at the traffic for the following network.
lo0 1.1.1.1 (R1)----(R2)----(R3) lo0 3.3.3.3
*The hop count for Lo0 on R1 arrives on R2 as a "metric of 1" according to
the sniffer.*
No. Time Source Destination Protocol
Info
4 17.200621 155.1.12.1 224.0.0.9 RIPv2
Response
Frame 4 (56 bytes on wire, 56 bytes captured)
Cisco HDLC
Internet Protocol, Src: 155.1.12.1 (155.1.12.1), Dst: 224.0.0.9 (224.0.0.9)
User Datagram Protocol, Src Port: router (520), Dst Port: router (520)
Routing Information Protocol
Command: Response (2)
Version: RIPv2 (2)
Routing Domain: 0
IP Address: 1.1.1.0, *Metric: 1*
*The Hop count of route as it leaves R2 going to R3 is 2*
No. Time Source Destination Protocol
Info
3 4.707069 155.1.23.2 224.0.0.9 RIPv2
Response
Frame 3 (76 bytes on wire, 76 bytes captured)
Cisco HDLC
Internet Protocol, Src: 155.1.23.2 (155.1.23.2), Dst: 224.0.0.9 (224.0.0.9)
User Datagram Protocol, Src Port: router (520), Dst Port: router (520)
Routing Information Protocol
Command: Response (2)
Version: RIPv2 (2)
Routing Domain: 0
IP Address: 1.1.1.0, *Metric: 2*
IP Address: 155.1.12.0, Metric: 1
This exercise seems to verify that the hop count is incremented by the
sender.
This can also be verified on the Router it's self instead of using a sniffer
(actually this way is MUCH simplier).
R2 receives the V2 update from R1 for 1.1.1.0/24 as hop count 1 as seen with
debug ip rip
R2#debug ip rip
RIP protocol debugging is on
R2#
*Mar 1 00:27:00.583: RIP: *received* v2 update from 155.1.12.1 on Serial0/0
*Mar 1 00:27:00.587: 1.1.1.0/24 via 0.0.0.0 in 1 hops
*Mar 1 00:30:42.415: RIP: *sending* v2 update to 224.0.0.9 via Serial0/1
(155.1.23.2)
*Mar 1 00:30:42.415: RIP: build update entries
*Mar 1 00:30:42.415: 1.1.1.0/24 via 0.0.0.0, *metric 2*, tag 0
I removed some the output to make it clear. We can see that the route for
1.1.1.0/24 arrives on int s0/0 with a hop count of 1 and is sent on S0/1 to
R3 with a hop count of 2.
If this information is incorrect please correct me.
Hope this helped.
Terry
On Sun, Sep 13, 2009 at 10:22 AM, Bryan Bartik <[email protected]> wrote:
> Hi Solomon,
>
> The receiving router uses the metric it hears from its neighbor. It
> increments upon sending it out.
>
> -hth
>
> On Sun, Sep 13, 2009 at 7:31 AM, Solomon Ayele <[email protected]> wrote:
>
>> Dears,
>> I have a question. When RIP updates are sent from one router and received
>> by the other what does the receiving router do to the advertised metric?
>> does it increment by 1 or does the advertising router send an update with
>> metric + 1 value? My expectation was the receiving router is the one that
>> does the increment.
>>
>> This question came as I have redistributed a loopback interface to RIP
>> with metric of 10 and on the neighboring router I saw it as having metric of
>> 10.
>>
>> Best Regards
>> Solomon
>>
>>
>> _______________________________________________
>> For more information regarding industry leading CCIE Lab training, please
>> visit www.ipexpert.com
>>
>>
>
>
> --
> Bryan Bartik
> CCIE #23707 (R&S), CCNP
> Sr. Support Engineer - IPexpert, Inc.
> URL: http://www.IPexpert.com
>
> _______________________________________________
> For more information regarding industry leading CCIE Lab training, please
> visit www.ipexpert.com
>
>
_______________________________________________
For more information regarding industry leading CCIE Lab training, please visit
www.ipexpert.com
