Was multicast routing behavior changed in new 15.0T code?

Hi GS Gurus.

Just ran into an strange issue with multicast routing where the router
wasn't getting the RP mapping information. The topology is very simple as it
is a daisy chain and no RPF failures:

SW---SW(RP)---SW---R

Router interface configuration

interface FastEthernet0/1
 ip address 61.61.128.193 255.255.255.224
 ip pim sparse-mode
 ip ospf mtu-ignore
 duplex auto
 speed auto
 ipv6 address 2001:61:100::4/64
 ipv6 rip RIPNG enable
 !

R4(config)#do sh ip pim rp map
PIM Group-to-RP Mappings

R4(config)#

So I turned on "debug ip mpacket" on the router to see what was going on,
and also tried to disable "mroute cache" as follows:

R4(config)#int fa0/1
R4(config-if)#no ip mroute-ca
The above command is going to be deprecated. Use MFIB commands instead.

Well, looks like this command is not supported anymore, so lets use the new
MFIB commands.

R4(config-if)#no ip mfib ?
  cef Multicast CEF to/from interface
  forwarding Multicast forwarding to/from interface

Not sure the difference between both, so will disable both. The final
configuration of the interface looks as follows:

interface FastEthernet0/1
 ip address 61.61.128.193 255.255.255.224
 ip pim sparse-mode
 no ip mfib forwarding input
 no ip mfib forwarding output
 no ip mfib cef input
 no ip mfib cef output
 ip ospf mtu-ignore
 duplex auto
 speed auto
 ipv6 address 2001:61:100::4/64
 ipv6 rip RIPNG enable
 !

And right after I'm done with that configuration -which was suppossed to be
used only for debugging purposes- I get the following message:

R4(config-if)#
*Aug 15 22:54:16.490: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Tunnel0, changed state to up

And now the RP mappings appear to be working:

R4(config-if)#do sh ip pim rp map
PIM Group-to-RP Mappings

Group(s) 239.10.5.0/24
  RP 150.1.9.9 (?), v2v1
    Info source: 150.1.10.10 (?), elected via Auto-RP
         Uptime: 00:01:52, expires: 00:02:05

Not sure what exactly is going on with the new code, but I had never seen
this before. First looks like the behavior is now like in IPv6 multicast,
where a tunnel interface is created, but I don't understand why it was
necessary to turn off MFIB for it to work.

Is anybody aware of this behavior? I couldn't find it documented.

R4(config-if)#do sh ver
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version
15.0(1)M2, RELEASE SOFTWARE (fc2)

Thanks,

Jorge

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Received on Mon Aug 16 2010 - 12:05:48 ART