Re: RPF failures on multicast over gre tunnel

From: Paul Cosgrove (paul.cosgrove@heanet.ie)
Date: Tue Apr 08 2008 - 08:31:28 ART

When a router running traditional IOS is determining the RPF interface,
it first looks at routes to the source with the lowest AD. Connected
will win over a static.

Alexei Monastyrnyi wrote:
> Hi.
>
> On R5 if you source your ping 224.2.2.2 from interface other than tunnel
> source while having a proper mroute for that IP on the other side,
> you'll get it alright. So the workaround for you would be in sourcing
> your tunnel from loopback interface.
>
> http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080094b55.shtml#noforwardrpffail
>
>
> But it seems like the RPF check sequence has a higher preference for
> directly connected interfaces with PIM enabled, not mentioned in the doc
> though. :-)
>
> 172.16.103.1 (lo103) R3 (Se 1/0) 172.16.123.3 ---FR--- 172.16.123.1 (Se
> 1/0) R1 (fa 0/0 172.16.11.1 joined 224.12.2.2)
>
> R1#conf t
> R1(config-if)#do sh run in tu 13 Building configuration...
>
> Current configuration : 152 bytes
> !
> interface Tunnel13
> ip unnumbered Serial1/0
> ip pim dr-priority 255
> ip pim dense-mode
> tunnel source Serial1/0
> tunnel destination 172.16.123.3
> end
>
> R1(config-if)#do sh run in ser 1/0
> Building configuration...
>
> Current configuration : 221 bytes
> !
> interface Serial1/0
> ip address 172.16.123.1 255.255.255.248
> encapsulation frame-relay
> serial restart-delay 0
> frame-relay map ip 172.16.123.1 103
> frame-relay map ip 172.16.123.3 103
> no frame-relay inverse-arp
> end
>
> R1(config-if)#do sh run | in mroute
> ip mroute 172.16.123.3 255.255.255.255 Tunnel13
>
> R1(config-if)#do sh ip rpf 172.16.123.3
> RPF information for ? (172.16.123.3)
> RPF interface: Tunnel13
> RPF neighbor: ? (172.16.123.3)
> RPF route/mask: 172.16.123.3/32
> RPF type: static
> RPF recursion count: 0
> Doing distance-preferred lookups across tables
>
> R1(config)#in ser 1/0 R1(config-if)#ip pim dense-mode
> R1(config-if)#do sh ip rpf 172.16.123.3
> RPF information for ? (172.16.123.3)
> RPF interface: Serial1/0
> RPF neighbor: ? (172.16.123.3) - directly connected
> RPF route/mask: 172.16.123.0/29
> RPF type: unicast (connected)
> RPF recursion count: 0
> Doing distance-preferred lookups across tables
>
> HTH
> A.
>
> theKonqueror said the following on 4/8/2008 11:57 AM:
>> Well, thats what the question says. "Enable pim dense mode on the link
>> between R4 and R5". The only link between the two is frame-relay.
>> Solution
>> guide has same config as I do, so I wonder they didn't check it?
>>
>> I'm running 12.4 adv-enterprise on routers btw...
>>
>> On Tue, Apr 8, 2008 at 3:17 PM, Sadiq Yakasai <sadiqtanko@gmail.com>
>> wrote:
>>
>>
>>> Hmmm,
>>>
>>> But if you are not mapping broadcast on the FR maps, then whats the
>>> point of enabling PIM on the serial interfaces?
>
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