ANY CAST ( Multicast Routing)

Any Cast Multicast 

• Any cast is a method to create redundancy 
• Traffic from source to destination reaches closest destination in the topology
• Multiple destinations share the same address and route to the closest one based on the IGP/BGP table 

Any Cast RP

• Use any cast load balancing to decentralize the placement of PIM spare mode RPs
• All RPs must share the same information about senders and receivers
• PIM register and join messages go to the closest RP in the topology
• If one RP goes down, convergence is up to IGP
• As long as one RP is up, new trees will be built up

MSDP

• MSDP uses to advertise (S,G) pair between RPs
• MSDP will make sure that PIM register is sent to one of the any cast RPs 
• Another RP will not get PIM join message
• MSDP will telll other RPs about (S,G) through an MSDP source active (SA) message
• Allow PIM domain to use independent RPs
• Any cast RPs are MSDP peers using unique address
• Router (config) # ip msdp peer x.x.x.x connect-source loopback xx
• Router (config) # ip msdp originator-id loopback xx

Where is going to use for?

• It is useful when multicast goes on internet and we have many sources and want closet source to your region will send you the stream

ANYCAST LAB

R2 CONFIGURATION

R2#show run | section msdp

ip msdp peer 3.3.3.3 connect-source Loopback0 

ip msdp cache-sa-state

ip msdp originator-id Loopback0

This is rp address and any cast address ( This address will be shared with R3)

ip pim rp-address 23.23.23.23

R2#show ip int brief

Interface                         IP-Address         OK? Method Status                Protocol

GigabitEthernet0/0         10.12.12.2       YES NVRAM  up                    up

GigabitEthernet1/0         10.23.23.2       YES NVRAM  up                    up

Loopback0                      2.2.2.2            YES NVRAM  up                    up

Loopback23                   23.23.23.23     YES NVRAM  up                    up  ( any cast)

Tunnel0                          23.23.23.23     YES unset        up                    up

Tunnel1                          23.23.23.23     YES unset        up                    up

R2#show ip pim nei

Neighbor          Interface                Uptime/Expires    Ver   DR

Address                                                            Prio/Mode

10.12.12.1        GigabitEthernet0/0       01:02:29/00:01:30 v2    1 / S P G

10.23.23.3        GigabitEthernet1/0       01:02:29/00:01:15 v2    1 / DR S P G

R2#

R2#show ip msdp peer

MSDP Peer 3.3.3.3 (?), AS ?

  Connection status:

    State: Up, Resets: 16, Connection source: Loopback0 (2.2.2.2)

    Uptime(Downtime): 00:00:29, Messages sent/received: 1/1

    Output messages discarded: 0

    Connection and counters cleared 01:04:59 ago

  SA Filtering:

    Input (S,G) filter: none, route-map: none

    Input RP filter: none, route-map: none

    Output (S,G) filter: none, route-map: none

    Output RP filter: none, route-map: none

  SA-Requests:

    Input filter: none

  Peer ttl threshold: 0

  SAs learned from this peer: 0

  Number of connection transitions to Established state: 17

    Input queue size: 0, Output queue size: 0

  MD5 signature protection on MSDP TCP connection: not enabled

  Message counters:

    RPF Failure count: 0

    SA Messages in/out: 0/0

    SA Requests in: 0

    SA Responses out: 0

    Data Packets in/out: 0/0

R3 CONFIGURATION 

should be the same as R2

Useful "SHOW" commands

• show ip msdp peer
• show ip msdp sa cache
• show ip pim neighbor
• show ip pim interface
• show ip pim rp mapping
• show ip mroute

Useful "DEBUG" commands

• debug ip pim
• debug ip msdp detail
• mtrace x.x.x

REFERENCE

1. https://ine.com/
2. https://tools.ietf.org/html/rfc4610
3. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/anycast.html
4. https://community.cisco.com/t5/network-architecture-documents/rp-redundancy-with-pim-sm-anycast-rp/ta-p/3116911