From: Bob Sinclair (bob@bobsinclair.net)
Date: Tue Oct 16 2007 - 16:45:44 ART
Julio Carrasco wrote:
> Hello Group,
>
> I have a silly trouble.
> If you have all your router configured with Sparse-mode, and autorp listener,
> and there are two routers claiming to be the RP for the same group (with ip
> pim send-rp-announce), What router will become the RP for the group ??
>
Julio,
Assuming everything else is equal, then the RP with the highest IP
address will be elected. However, you can prefer a lower-addressed RP
by providing a longer match on a group-list. In the example below R2
and R5 are configured as candidate RPs. But R2 (address 2.0.0.1) has a
longer match on its group-list than R5 (address 5.0.0.1) As you see,
R2 is elected the RP for group 239.255.1.1 even though it has the lower
ip address.
R5#sh ip pim rp mapping
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent
Group(s) 239.255.0.0/16
RP 5.0.0.1 (?), v2v1
Info source: 5.0.0.1 (?), elected via Auto-RP
Uptime: 00:04:38, expires: 00:02:20
Group(s) 239.255.1.1/32
RP 2.0.0.1 (?), v2v1
Info source: 2.0.0.1 (?), elected via Auto-RP
Uptime: 00:01:34, expires: 00:02:25
R5#sh ip mroute 239.255.1.1
IP Multicast Routing Table
[removed for brevity]
(*, 239.255.1.1), 00:05:55/00:02:57, RP 2.0.0.1, flags: SJCL <<<<<<<<<
Incoming interface: Serial1/0, RPF nbr 172.16.25.2
Outgoing interface list:
Loopback5, Forward/Sparse, 00:05:55/00:02:57
R5#
Here are the relevant configs:
On R2:
interface Loopback2
ip address 2.0.0.1 255.255.255.0
ip pim sparse-mode
ip igmp join-group 239.255.1.1
ip pim autorp listener
ip pim send-rp-announce Loopback2 scope 15 group-list 2
ip pim send-rp-discovery Loopback2 scope 15
!
access-list 2 permit 239.255.1.1 <<<<<Note the host mask<<<<<<
And on R5:
interface Loopback5
ip address 5.0.0.1 255.255.255.0
ip pim sparse-mode
ip igmp join-group 239.255.1.1
ip pim autorp listener
ip pim send-rp-announce Loopback5 scope 15 group-list 5
ip pim send-rp-discovery scope 15
!
access-list 5 permit 239.255.0.0 0.0.255.255 <<<Note the /24 mask<<<<<<
Hope that helps!
--Bob Sinclair CCIE 10427 CCSI 30427 www.netmasterclass.net
This archive was generated by hypermail 2.1.4 : Fri Nov 16 2007 - 13:11:15 ART