Re: MCast GRE Tunnel

John,
It's easy to fix the rpf problem and your mcast will work.
Fixing your RFP:
If you show the routes installed at your local router, you will see that in
order to reach the remote host ip(172.16.16.1 for instance) your router know
how to arrive using the serial interface(PPP/framerelay). Your multicast
traffic should be sourcered by other IP address, fo instance
192.168.100.100. So the check who is failing is the way to reach
192.168.100.100 not 172.16.16.1
You need to install a route to 192.168.100.100 through GRE tunnel. At this
point, your RPF will match the way and the return of the packet and
multicast traffic will flow.

-------------------------------R1--s0/1(ip
172.16.16.2)-------------s0/1-(ip
172.16.16.1)----R2------------------------192.168.100.100(Multicast
source)
          gre tunnel 1 ip unnumbered
s0/ gre tunnel 1
ip unnumbered s0/1

Solution:
Ip route 192.168.100.100 255.255.255.255 tunnel 1 (Leaving the packet at
"wire")
or even: ip route 192.168.100.100 255.255.255.255 172.16.16.1 (Only if
172.16.16.1 appears as directly connected through tunnel 1 )

Please check the solution provided to continue troubleshooting it.
hth
Rob

http://robclavbcn.blogspot.com
www.kubsolutions.com

2010/10/18 Edward John <edwardjohn2020_at_googlemail.com>

> Hi Rob,
>
> In case if ASBR connection is PPP / Frame-relay, remote host ip (/32) is
> installed in the local routing table. This cause me RPF failure (while
> forwarding mcast traffic out of tunnel) if I use Serial interface IP for
> Tunnel.
>
> I couldn't succeed by using loopback ip as well, but still couldn't figure
> out the root cause for that....
>
>
> Regards,
> John
>
>
> On Mon, Oct 18, 2010 at 1:56 PM, Rob Clav <robclav_at_gmail.com> wrote:
>
>> Hi Edward,
>> it depends on the expecific q|estion. If It tells you explicitelly that
>> you aren't allowed to use an additional IP or if it tells you that you are
>> allowed to use it. If there's nothing about it, and as a default action I
>> recommend to you borrow an existent Ip address from other interface or
>> loopback using the ip unnumbered command in order to avoid non wished
>> behaviours or implicit exam conditions.
>> HTH,
>> robclav
>>
>> http://robclavbcn.blogspot.com
>> www.kubsolutions.com
>>
>>
>>
>> 2010/10/16 Edward John <edwardjohn2020_at_googlemail.com>
>>
>>> Hi GS,
>>>
>>> In Inter-domain multicast scenario;
>>>
>>> If we need to create a GRE tunnel between two ASBR to pass mcast traffic,
>>> can we assign any new IP subnet for the tunnel interface in the exam?
>>> I mean can we randomly assigned any IP address for tunnel interface?
>>> *
>>> *
>>> *
>>> *
>>> --
>>>
>>> *Regards,*
>>> *John*
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
>>> Subscription information may be found at:
>>> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Mon Oct 18 2010 - 17:49:05 ART