RE: forming RIPv2 adjacency in unicast?

We do have a lab that deals with this exact scenario, and yes the answer is
to use a static NAT translation, similar to what Jose said. However, it
deals with unicasting only from R1 to R2, not both ways.

So lets go through it step by step: R1 Fa0/0 --- Fa0/0 R2
R1 fa0/0: 10.0.0.1
R2 fa0/0: 10.0.0.2

R1:
int fa0/0
 ip nat outside

ip nat outside source static udp 10.0.0.2 520 224.0.0.9 520

So the NAT statement essentially says "If I see a packet sourced from
10.0.0.2:520 on my fa0/0 interface, change the source to 224.0.0.9:520" --
which doesn't make a lot of sense...I mean why would you make the SOURCE a
multicast address? You wouldn't -- the "money" is when you see the opposite
is also true -- "If I am SENDING a packet out my fa0/0 interface DESTINED TO
224.0.0.9:520 , change the DESTINATION to 10.0.0.2:520" which is where you
get your unicast.

OK, so stepping through it -- R2 sends a multicast RIPv2 packet just as it
always would on the ethernet. Source: 10.0.0.2:520 , Destination:
224.0.0.9:520. R1 receives the packet on it's fa0/0 interface and because
it has "ip nat outside" as well as the NAT statement above it recognizes
"hey the source is 10.0.0.2:520 , I need to translate that immediately!" At
this point, R1 now has a NAT translation in it's NAT table!

Now, R1 wants to send a RIPv2 update on to the ethernet...OK the RIP process
sends an update -- Source: 10.0.0.1:520 , Destination: 224.0.0.9:520
...BOOM, your NAT rule kicks in, and translates the packet as Source:
10.0.0.1:520 , Destination: 10.0.0.2: 520

It is a dirty, and tricky manipulation that hopefully none of us will ever
need to use in real life! : ) I truly hope that helps you out.

Regards,

Joe Astorino
CCIE #24347 (R&S)
Sr. Support Engineer - IPexpert, Inc.
URL: http://www.IPexpert.com
 
-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Jose
Miguel Huertas
Sent: Thursday, May 21, 2009 5:55 AM
To: Cisco certification
Cc: qospf qospf
Subject: RE: forming RIPv2 adjacency in unicast?

Hi Salah,

Let's put the next scenario:

            R1 [fa0/0] ---- [Fa0/0] R2

Lo0 R1: 1.1.1.1 /32
Fa0/0 R1: 12.12.12.1/24

Lo0 R2: 2.2.2.2/32
FA0/0 R2: 12.12.12.2/24

On R1:

int fa0/0
 ip nat outside
ip nat outside source static udp 2.2.2.2 520 224.0.0.9 520 ip route 2.2.2.2
255.255.255.255 fa0/0 12.12.12.2

On R2:

int fa0/0
 ip nat outside
ip nat outside source static udp 1.1.1.1 520 224.0.0.9 520 ip route 1.1.1.1
255.255.255.255 fa0/0 12.12.12.1

Try this, it works. I'm sure there is another way to do it, but this one
goes good.

________________________________
De: Salah ElShekeil [mailto:salah.elshekeil_at_gmail.com]
Enviado el: jueves, 21 de mayo de 2009 10:30
Para: Jose Miguel Huertas
CC: qospf qospf; Cisco certification
Asunto: Re: forming RIPv2 adjacency in unicast?

did u try it? I haven't seen this :-D ,

if possible please post the lab conf.
On Thu, May 21, 2009 at 11:25 AM, Jose Miguel Huertas
<JoseMiguel.huertas_at_telindus.es<mailto:JoseMiguel.huertas_at_telindus.es>>
wrote:
This is one of the most weird things I've seen. You have to use NAT to
translate the multicast address into a unicast address.

-----Mensaje original-----
De: nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>
[mailto:nobody_at_groupstudy.com<mailto:nobody_at_groupstudy.com>] En nombre de
Salah ElShekeil Enviado el: jueves, 21 de mayo de 2009 9:46
Para: qospf qospf
CC: Cisco certification
Asunto: Re: forming RIPv2 adjacency in unicast?

how u would do it without neighbor command?

by default RIPv2 to multicast group , the only command will change this
behavior to unicast is neighbor command :-) ,

On Thu, May 21, 2009 at 10:28 AM, qospf qospf
<cisco.qospf_at_gmail.com<mailto:cisco.qospf_at_gmail.com>> wrote:

> Hi,
>
> what are the ways of forming RIPv2 adjacency using unicast only (no
> bcast/multicast allowed) assuming that you can't use the neighbor
> command....any ideas?
>
> thx
>
> --
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Salah
CCIE# 24207
Blogs and organic groups at http://www.ccie.net<http://www.ccie.net/>