PIM RP Load Balancing and Redundancy

Here look at achieving load-balancing and redundancy of multicast traffic between RPS.

First load-balancing

Auto-RP is being used. SW1 is configured as RP for 224.0.0.0 - 231.255.255.255 and
SW3 is RP for 232.0.0.0 239.255.255.255.

SW1
ip pim send-rp-announce Loopback0 scope 16 group-list 11
ip access-list st 11
permit 224.0.0.0 7.255.255.255

SW3
ip pim send-rp-announce Loopback0 scope 16 group-list 11
ip access-list st 11
permit 232.0.0.0 7.255.255.255

Now examining the rp mapping on the RP we can see the load is balanced between SW1 (150.1.7.7) and SW3 (150.1.9.9).

Router_5>s ip pim rp map
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent (Loopback0)

Group(s) 224.0.0.0/5
RP 150.1.7.7 (?), v2v1
Info source: 150.1.7.7 (?), elected via Auto-RP
Uptime: 00:00:06, expires: 00:02:53
Group(s) 224.0.0.0/4
RP 150.1.5.5 (?), v2v1
Info source: 150.1.5.5 (?), elected via Auto-RP
Uptime: 00:13:55, expires: 00:02:11
Group(s) 232.0.0.0/5
RP 150.1.9.9 (?), v2v1
Info source: 150.1.9.9 (?), elected via Auto-RP
Uptime: 00:00:31, expires: 00:02:24



Next step is to achieve redundancy. Make SW1 backup SW3 should it fail and vice versa.

This can be achieved by defining each candidate RP with the same duplicate range. The mapping agent will select the RP with the highest ip address.

So on SW1 and SW3 i update access list 11 as follows:-

ip access-list st 11
permit 224.0.0.0 15.255.255.255

Router_5>show ip pim rp map 224.0.0.0
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)
This system is an RP-mapping agent (Loopback0)

Group(s) 224.0.0.0/5
RP 150.1.7.7 (?), v2v1
Info source: 150.1.7.7 (?), elected via Auto-RP
Uptime: 00:07:38, expires: 00:02:21
Group(s) 224.0.0.0/4
RP 150.1.9.9 (?), v2v1
Info source: 150.1.9.9 (?), elected via Auto-RP
Uptime: 00:02:01, expires: 00:01:56
RP 150.1.7.7 (?), v2v1
Info source: 150.1.7.7 (?), via Auto-RP
Uptime: 00:01:38, expires: 00:02:18
RP 150.1.5.5 (?), v2v1
Info source: 150.1.5.5 (?), via Auto-RP
Uptime: 00:21:27, expires: 00:02:46

The mapping agent shows SW3 as the winning candidate RP for the 224.0.0.0/4 range. On other routers only the winning RP will be shown in the rp map table.


Router_6>s ip pim rp map

PIM Group-to-RP Mappings
Group(s) 224.0.0.0/4
RP 150.1.9.9 (?), v2v1
Info source: 150.1.5.5 (?), elected via Auto-RP
Uptime: 00:04:10, expires: 00:02:42


Note. When selecting ranges to advertise the mapping agent will always advertise the longest match mcast range.