[cisco-voip] IP PIM Passive - Yuck!

[Carter, Bill]

For the benefit of the archives I wanted to post my results/findings.

I was having problems delivering MOH to remote phones. Here is the
network layout:


CallManager (VLAN 101) -- Cat 4500 -- VLAN 503 --- Catalyst 3560 IP Base
-- (VLAN 103) --- IP Phone
					     |		|
					     ---VLAN 502---

The problem I had was due to 2 equal cost routes from the core to the
remote. Multicast uses the unicast route table to route packets, the
Unicast table decided to use 1 path, but multicast delivered packets
across the other path. On the Remote switch, debug ip mpacket showed rpf
failures.

My fix was to adjust the metrics in the route advertisements sent out
from the Cat 4500 so there was only 1 route back to VLAN 101.


With this exercise I learned how to configure IGMP Stub (Proxy)
multicast routing. In this scenario I was able to get past the
limitations of IP PIM PASSIVE. With PIM PASSIVE, the Catalyst 3560s with
IP Base can pass PIM traffic but not participate in PIM. IGMP Stub
(Proxy) essentially removes the dependency on PIM routing at the
Catalyst 3560 level. I am not positive, but I believe the "ip igmp
helper-address" could have been 10.101.254.1.


! Remote Catalyst 3560
ip multicast-routing distributed
!
ip pim rp-address 10.101.254.1


interface Vlan103
 Description REMOTE VOICE VLAN
 ip address 10.103.254.10 255.255.0.0
 ip pim passive
 ip igmp helper-address 172.16.103.1
 ip igmp version 3
!
interface Vlan503
 ip address 172.16.103.2 255.255.255.0
 ip pim passive
 ip igmp version 3
!
! *****
! Core Router
!
ip pim rp-address 10.101.254.1
!
interface Vlan503
 ip address 172.16.103.1 255.255.255.0
 ip pim sparse-mode
 ip igmp version 3
 ip igmp proxy-service
!
interface Vlan 101
 Description CORE VOICE VLAN
 ip address 10.101.254.1 255.255.0.0
 ip pim sparse-mode
 ip igmp version 3


-----Original Message-----
From: Go0se [mailto:me at go0se.com] 
Sent: Wednesday, July 14, 2010 9:53 AM
To: Carter, Bill; cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] IP PIM Passive - Yuck!

Pim passive keeps the router from sending or receiving pim messages on a
specific interface. I don't know how you have it configured but you do
not
want to use ip pim passive on networks with more than one multicast
router.
It can result in duplicate traffic or even loops.

Thanks,

Go0se

My blog: 
http://atc.go0se.com

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Help Hopegivers International 
feed the orphans of India.
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-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Carter, Bill
Sent: Tuesday, July 13, 2010 3:54 PM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] IP PIM Passive - Yuck!

Any "successful" experiences with the IP PIM Stub routing feature (ip
pim passive) in the Catalyst IP Base software?

I have gotten Multicast MOH to work with using ip pim passive when the
phone is a hop away from CallManager. I know have a situation where the
phone is 3 hops away (3 layer hops, 5 physical switches) and Multicast
MOH doesn't work.

In UCM, MOH Server configuration, the multicast hop count is 6.





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