Introduction
You can achieve redundancy for the Rendezvous Point (RP) by using protocols such as Auto-RP and Bootstrap Protocol. However, their convergence may not be rapid in the event of a failure. The concept of Anycast RP addresses this issue. In Anycast RP, the same IP address (rp-address) is configured on two or more routers designated to function as RP. This IP is then advertised within the Interior Gateway Protocol (IGP). As a result, other routers select an RP based on the best path to the rp-address. If there's a failure, convergence occurs as quickly as the IGP itself.
A challenge with Anycast RP is that information must be synchronized between the RPs, as some senders and receivers may join one RP while others join a different one. Without synchronization, these routers would not have complete source information, leading to potential multicast disruption. To resolve this, a mechanism is required to sync source-related information among all routers acting as RPs. Two protocols can fulfill this function:
Multicast Source Discovery Protocol (MSDP)
Protocol Independent Multicast (PIM)
MSDP is a well-established protocol. It sends Source Active messages to other routers whenever a source registers with an RP. There is also an enhancement to PIM, which is currently exclusive to Nexus devices. To make it work in IOS-XE devices for IPV4, you need to use Anycast-RP MSDP flavour.
Components used:
CML is used to replicate the use case
-> CSR1000v Routers working as Source and Destination.
-> Two Nexus C9000V boxes used as Anycast-RP PIM.
-> CSR1000v Router working as Anycast-RP MSDP.
Topology as follows:
First part of the lab, we will configure Anycast-RP on Nexus boxes and test the traffic.
In second, part we will migrate from Anycast-RP PIM to Anycast-RP MSDP and test the traffic.
PART 1:
Anycast-RP PIM Configuration
Source:
-> Running EIGRP as IGP for reachability. Establishing EIGRP with Nexus on GigabitEthernet1.
sh run | sec eigrp
router eigrp 1
network 0.0.0.0
!
interface GigabitEthernet1
ip address 192.168.1.1 255.255.255.0
negotiation auto
no mop enabled
no mop sysid
end
----------------------------
Nexus-ANYCAST-RP-Core-1:
-> Running EIGRP as IGP for reachability. Establishing EIGRP neighborship with all boxes shown in diagram.
-> Running PIM sparse mode on all the interfaces on the Nexus box.
-> Loopback0 is used as Anycast-RP source to exchange SA messages, which is 172.16.158.110/32.
-> Loopback7 is used as Anycast-RP address, which is 172.16.158.248/32.
interface loopback0
ip address 172.16.158.110/32
ip router eigrp 1
ip pim sparse-mode
!
interface loopback7
ip address 172.16.158.248/32
ip router eigrp 1
ip pim sparse-mode
!
interface Ethernet1/1
no switchport
ip address 192.168.2.1/24
ip router eigrp 1
ip pim sparse-mode
no shutdown
!
interface Ethernet1/2
no switchport
ip address 192.168.3.1/24
ip router eigrp 1
ip pim sparse-mode
no shutdown
!
interface Ethernet1/3
no switchport
ip address 192.168.1.2/24
ip router eigrp 1
ip pim sparse-mode
no shutdown
ip pim rp-address 172.16.158.248 group-list 224.0.0.0/4 override
ip pim anycast-rp 172.16.158.248 172.16.158.110
ip pim anycast-rp 172.16.158.248 172.16.158.111
!
---------------------
Nexus-ANYCAST-RP-Core-2:
-> Running EIGRP as IGP for reachability. Establishing EIGRP neighborship with all boxes shown in diagram.
-> Running PIM sparse mode on all the interfaces on the Nexus box.
-> Loopback0 is used as Anycast-RP source to exchange SA messages, which is 172.16.158.111/32.
-> Loopback7 is used as Anycast-RP address, which is 172.16.158.248/32.
interface loopback0
ip address 172.16.158.111/32
ip router eigrp 1
ip pim sparse-mode
!
interface loopback7
ip address 172.16.158.248/32
ip router eigrp 1
ip pim sparse-mode
!
interface Ethernet1/1
no switchport
ip address 192.168.3.2/24
ip router eigrp 1
ip pim sparse-mode
!
interface Ethernet1/2
no switchport
ip address 192.168.5.2/24
ip router eigrp 1
no shutdown
!
interface Ethernet1/3
no switchport
ip address 192.168.4.2/24
ip router eigrp 1
ip pim sparse-mode
no shutdown
!
ip pim rp-address 172.16.158.248 group-list 224.0.0.0/4 override
ip pim anycast-rp 172.16.158.248 172.16.158.110
ip pim anycast-rp 172.16.158.248 172.16.158.111
-------------------
Destination#
-> GigabitEthernet1 is joining multicast group 239.1.1.1
-> Static RP is configured as 172.16.158.248.
-> Running EIGRP as IGP for reachability.
sh run int gig1
Building configuration...
Current configuration : 170 bytes
!
interface GigabitEthernet1
ip address 192.168.5.1 255.255.255.0
ip pim sparse-mode
ip igmp join-group 239.1.1.1
negotiation auto
no mop enabled
no mop sysid
end
!
ip pim rp-address 172.16.158.248
!
router eigrp 1
network 0.0.0.0
!
-----------------------
OUTPUTS of Anycast-RP PIM:
Source#
-> Source can reach the Destination ip 192.168.5.1.
-> When we ping the multicast group 239.1.1.1, we can see the destination ip is responding.
ping 192.168.5.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.5.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/6/7 ms
Source#ping 239.1.1.1 re 5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 239.1.1.1, timeout is 2 seconds:
Reply to request 0 from 192.168.5.1, 15 ms
Reply to request 1 from 192.168.5.1, 13 ms
Reply to request 2 from 192.168.5.1, 15 ms
Reply to request 3 from 192.168.5.1, 11 ms
Reply to request 4 from 192.168.5.1, 15 ms
--------------
Nexus-ANYCAST-RP-Core-1#
-> Nexus Core-1 is creating PIM neighborship with other Nexus Core-2.
-> Anycast-RP is configured 172.16.158.248 for all the groups.
-> We can see mroute table is populated with incoming interface, OIL for the group 239.1.1.1/32.
show ip pim rp
PIM RP Status Information for VRF "default"
BSR disabled
Auto-RP disabled
BSR RP Candidate policy: None
BSR RP policy: None
Auto-RP Announce policy: None
Auto-RP Discovery policy: None
Anycast-RP 172.16.158.248 members:
172.16.158.110* 172.16.158.111
RP: 172.16.158.248*, (0),
uptime: 00:51:26 priority: 255,
RP-source: (local),
group ranges:
224.0.0.0/4
sh ip pim neighbor
PIM Neighbor Status for VRF "default"
Neighbor Interface Uptime Expires DR Bidir- BFD
ECMP Redirect
Priority Capable State
Capable
192.168.2.2 Ethernet1/1 00:30:49 00:01:23 1 no n/a
no
show ip mroute
IP Multicast Routing Table for VRF "default"
(192.168.1.1/32, 239.1.1.1/32), uptime: 00:07:59, ip pim
Incoming interface: Ethernet1/3, RPF nbr: 192.168.1.1, internal
Outgoing interface list: (count: 1)
Ethernet1/1, uptime: 00:04:22, pim
--------------------------
Nexus-ANYCAST-RP-Core-1#
-> Nexus Core-2 is creating PIM neighborship with other Nexus Core-1.
-> Anycast-RP is configured 172.16.158.248 for all the groups.
-> We can see mroute table is populated with incoming interface, OIL for the group 239.1.1.1/32.
Core-2# show ip pim rp
PIM RP Status Information for VRF "default"
BSR disabled
Auto-RP disabled
BSR RP Candidate policy: None
BSR RP policy: None
Auto-RP Announce policy: None
Auto-RP Discovery policy: None
Anycast-RP 172.16.158.248 members:
172.16.158.110 172.16.158.111*
RP: 172.16.158.248*, (0),
uptime: 01:04:51 priority: 255,
RP-source: (local),
group ranges:
224.0.0.0/4
Core-2# sh ip pim ne
PIM Neighbor Status for VRF "default"
Neighbor Interface Uptime Expires DR Bidir- BFD
ECMP Redirect
Priority Capable State
Capable
192.168.5.1 Ethernet1/2 00:14:05 00:01:27 1 no n/a
no
192.168.4.1 Ethernet1/3 00:43:06 00:01:28 1 no n/a
no
Core-2# show ip mroute
IP Multicast Routing Table for VRF "default"
(192.168.1.1/32, 239.1.1.1/32), uptime: 00:17:49, msdp mrib pim ip
Incoming interface: Ethernet1/3, RPF nbr: 192.168.4.1, internal
Outgoing interface list: (count: 1)
Ethernet1/2, uptime: 00:14:12, mrib
----------------------------
PART 2:
Migrating Anycast-RP PIM to Anycast-RP MSDP:
Let's introduce New-Core(IOS-XE-ANYCAST-RP-MSDP) box CSR1000v in the topology and configure Anycast-RP MSDP flavor this time.
We need to shutdown the Loopback0 and Loopback7 on Nexus Core-2 and create the same Loopback interfaces
on IOS-XE box.
New Configuration for Anycast-RP MSDP on Nexus Core-1:
-> We need to disable Anycast-RP PIM.
-> Enable MSDP peer configuration for New-Core.
Nexus-ANYCAST-RP-Core-1#
!
no ip pim anycast-rp 172.16.158.248 172.16.158.110
no ip pim anycast-rp 172.16.158.248 172.16.158.111
!
ip pim rp-address 172.16.158.248 group-list 224.0.0.0/4 override
!
ip msdp originator-id loopback0
ip msdp peer 172.16.158.111 connect-source loopback0
!
---------------------
Nexus-ANYCAST-RP-Core-1#
-> Shutdown the Loopback0 and Loopback7 to make sure Core-2 does not take part in Anycast-RP election.
-> Remove Anycast-RP PIM configuration from box.
interface Loopback0
shutdown
!
interface Loopback7
shutdown
!
no ip pim anycast-rp 172.16.158.248 172.16.158.110
no ip pim anycast-rp 172.16.158.248 172.16.158.111
!
----------------------
IOS-XE-ANYCAST-RP-MSDP:
-> Created same Loopback0 and Loopback7 on New-Core which were created on Core-2.
-> Created Static RP.
-> Created MSDP peer configuration.
interface Loopback0
ip address 172.16.158.111 255.255.255.255
ip pim sparse-mode
end
!
interface Loopback7
ip address 172.16.158.248 255.255.255.255
ip pim sparse-mode
end
!
interface GigabitEthernet1
ip address 192.168.2.2 255.255.255.0
ip pim sparse-mode
negotiation auto
no mop enabled
no mop sysid
end
!
interface GigabitEthernet2
ip address 192.168.4.1 255.255.255.0
ip pim sparse-mode
negotiation auto
no mop enabled
no mop sysid
end
!
router eigrp 1
network 0.0.0.0
!
ip pim rp-address 172.16.158.248
sh run | i msdp
ip msdp peer 172.16.158.110 connect-source Loopback0
ip msdp cache-sa-state
ip msdp originator-id Loopback0
-----------------------
OUTPUTS after Change to Anycast-RP MSDP:
Source#
-> Can ping the multicast group 239.1.1.1.
ping 239.1.1.1 re 50
Type escape sequence to abort.
Sending 50, 100-byte ICMP Echos to 239.1.1.1, timeout is 2 seconds:
Reply to request 0 from 192.168.5.1, 18 ms
Reply to request 1 from 192.168.5.1, 13 ms
Reply to request 2 from 192.168.5.1, 15 ms
Reply to request 3 from 192.168.5.1, 17 ms
Reply to request 4 from 192.168.5.1, 13 ms
Reply to request 5 from 192.168.5.1, 12 ms
------------------------
Nexus-ANYCAST-RP-Core-1#
-> We can see Anycast-RP is configured.
-> Mroute table is populated.
-> Can see now MSDP neighborship created with new IOS-XE box.
show ip pim rp
PIM RP Status Information for VRF "default"
BSR disabled
Auto-RP disabled
BSR RP Candidate policy: None
BSR RP policy: None
Auto-RP Announce policy: None
Auto-RP Discovery policy: None
RP: 172.16.158.248*, (0),
uptime: 01:36:04 priority: 255,
RP-source: (local),
group ranges:
224.0.0.0/4
sh ip mroute
(192.168.1.1/32, 239.1.1.1/32), uptime: 00:02:56, ip pim
Incoming interface: Ethernet1/3, RPF nbr: 192.168.1.1, internal
Outgoing interface list: (count: 1)
Ethernet1/1, uptime: 00:02:46, pim
show ip msdp summary
MSDP Peer Status Summary for VRF "default"
Local ASN: 0, originator-id: 172.16.158.110
Number of configured peers: 1
Number of established peers: 1
Number of shutdown peers: 0
Peer Peer Connection Uptime/ Last msg (S,G)s
Address ASN State Downtime Received Received
172.16.158.111 0 Established 00:16:30 00:00:21 0
--------------------------
IOS-XE-ANYCAST-RP-MSDP:
-> We can see Anycast-RP is configured.
-> Mroute table is populated with MT Flag.
M - MSDP created entry
T - SPT-bit set
-> Can see now MSDP neighborship created with new IOS-XE box.
sh ip pim rp
Group: 239.1.1.1, RP: 172.16.158.248
Group: 224.0.1.40, RP: 172.16.158.248
show ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
L - Local, P - Pruned, R - RP-bit set, F - Register flag,
T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet,
X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
U - URD, I - Received Source Specific Host Report,
Z - Multicast Tunnel, z - MDT-data group sender,
Y - Joined MDT-data group, y - Sending to MDT-data group,
G - Received BGP C-Mroute, g - Sent BGP C-Mroute,
N - Received BGP Shared-Tree Prune, n - BGP C-Mroute suppressed,
Q - Received BGP S-A Route, q - Sent BGP S-A Route,
V - RD & Vector, v - Vector, p - PIM Joins on route,
x - VxLAN group, c - PFP-SA cache created entry,
* - determined by Assert, # - iif-starg configured on rpf intf,
e - encap-helper tunnel flag, l - LISP Decap Refcnt Contributor
Outgoing interface flags: H - Hardware switched, A - Assert winner, p - PIM Join
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(192.168.1.1, 239.1.1.1), 00:09:46/00:01:48, flags: MT
Incoming interface: GigabitEthernet1, RPF nbr 192.168.2.1
Outgoing interface list:
GigabitEthernet2, Forward/Sparse, 00:09:46/00:03:12
show ip msdp summary
MSDP Peer Status Summary
Peer Address AS State Uptime/ Reset SA Peer Name
Downtime Count Count
172.16.158.110 ? Up 00:14:51 1 1 ?
Note: Anycast-RP PIM is supported for IPV6 in IOS-XE boxes. However, to run Anycast RP for IPV4 there is only one way MSDP.