Multicast lab 4: Any-Source Multicast with Bootstrap Router (BSR)

After giving a two-days training to a customer on multicast technology, I take the opportunity to have my lab and the configurations ready to share with you a suite of five different multicast configurations examples. And, how to make some tests and troubleshooting. These examples are based on the labs I used to practice the CCIE R&S practical exam.

Content of the posts

 

Including, for each topic:

  1. A network drawing
  2. The configuration details.
  3. The tests and debug outputs.
  4. When possible, a failover test and debug outputs.
  5. Some basic troubleshooting.

 

Any-source multicast (ASM) with bootstrap router (BSR)

 

Lab design and description

The network design is the same for every scenario:

I use four layer-3 Cisco 3650 catalyst switches running IOS-XE. With layer-3 ptp interfaces between them to create a small layer-3 network. OSPF is running between the switches to advertise all the networks: the ptp networks, the loopback0 interfaces and the VLAN10 of SW-1, where is the multicast source.

For the multicast source, I use a laptop running two VLC instances, sending video stream traffic to 233.1.2.3 and 234.1.2.3, both on port 30’001.

The receiver will be simulated by the loopback0 interface of SW-4.

 (Click on the image to see a larger version)

 

On this scenario, we will use the loopback0 of SW-2 as PIMv2 RP and bootstrap router (BSR).

BSR is like AutoRP, but does not use any dense-mode group. Candidates RPs (cRP) propose themselves as RP which is then flooded (RP-Set) to all PIM neighbors inside a bootstrap message (BSM). RP election is based on the higher priority (default = 0) or highest IP address. cRP learn the BSR IP address from the BSM and only 1 RP will be selected per group or group-range.

 

 

Configuration

First, we need to configure PIM on the interfaces between the four switches, on the interface where is source is located (VLAN10 of SW-1), the interface of the clients or receivers (in this case, the loopback0 of SW-4) and the loopback0 of SW-2. For this, we use the ip pim spare-mode command.

Do not forget to also configure ip multicast-routing, like below:

SW-1,2,3,4:
SW-X(config)#ip multicast-routing

SW-1,2,3,4: on the ptp interfaces, VLAN10 of SW-1, lo0 of SW-2 and SW-4: 
SW-X(config-if)#ip pim sparse-mode

 

Then, we configure the rp-candidate and the bsr-candidate. For the RP, I specify the group 233.1.2.3 with the access-list 11 and the priority to 255:

SW-2#config t
Enter configuration commands, one per line. End with CNTL/Z.
SW-2(config)#ip pim bsr-candidate lo0
!
SW-2(config)#access-list 11 permit 233.1.2.3
!
SW-2(config)#ip pim rp-candidate lo0 group-list 11 priority 255

 

 

Tests and debugging

 

Before any IGMP join

First, let’s check the RP mapping on the four switches:

SW-X#show ip pim rp mapping 
PIM Group-to-RP Mappings

Group(s) 233.1.2.3/32
RP 2.2.2.2 (?), v2
Info source: 2.2.2.2 (?), via bootstrap, priority 255, holdtime 150
Uptime: 00:03:29, expires: 00:01:43

 

 

IGMP join

Now, let’s make an IGMP join for the group 233.1.2.3 on the loopback0 of SW-4.

SW-4#config t
SW-4(config)#int lo
SW-4(config-if)#ip igmp join-group 233.1.2.3

 

At this point, exactly as we seen on lab-1, we can see on the multicast routing table of SW-4 that the multicast traffic is coming through SW-3, because it uses shortest-path tree (T flag):

SW-4#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, 
       V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 233.1.2.3), 00:01:44/stopped, RP 2.2.2.2, flags: SJCL
  Incoming interface: GigabitEthernet1/0/2, RPF nbr 10.10.24.2
  Outgoing interface list:
    Loopback0, Forward/Sparse, 00:01:44/00:02:46

(10.10.10.10, 233.1.2.3), 00:01:44/00:01:15, flags: LJT
  Incoming interface: GigabitEthernet1/0/3, RPF nbr 10.10.34.3
  Outgoing interface list:
    Loopback0, Forward/Sparse, 00:01:44/00:02:46

 

We can also see traffic statistics with the command: show ip mroute count:

SW-4#show ip mroute count 
Use "show ip mfib count" to get better response time for a large number of mroutes.

IP Multicast Statistics
3 routes using 1544 bytes of memory
2 groups, 0.50 average sources per group
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 233.1.2.3, Source count: 1, Packets forwarded: 34605, Packets received: 34608
  RP-tree: Forwarding: 2/0/0/0, Other: 2/0/0
  Source: 10.10.10.10/32, Forwarding: 34603/142/355/393, Other: 34606/1/2

 

 

Failover test

Let’s test the following: configure another BSR and RP-candidate on SW-3, with a lowest priority. Then, shutdown the RP on SW-2:

 

  • Configuration of the new BSR and RP candidates on SW-3:
SW-3(config)#ip pim bsr-candidate Loopback0 
SW-3(config)#ip pim rp-candidate Loopback0 group-list 11 priority 100

 

  • Check the RP mappings:
SW-4#show ip pim rp map
PIM Group-to-RP Mappings

Group(s) 233.1.2.3/32
RP 3.3.3.3 (?), v2
Info source: 3.3.3.3 (?), via bootstrap, priority 100, holdtime 150
Uptime: 00:00:34, expires: 00:01:53
RP 2.2.2.2 (?), v2
Info source: 3.3.3.3 (?), via bootstrap, priority 255, holdtime 150
Uptime: 00:13:18, expires: 00:01:53

Now, we have two RP for 233.1.2.3: 2.2.2.2 with a priority of 255 and 3.3.3.3 with a priority of 100.

 

  • Check the BSR-router:
SW-4#show ip pim bsr-router 
PIMv2 Bootstrap information
BSR address: 3.3.3.3 (?)
Uptime: 00:01:38, BSR Priority: 0, Hash mask length: 0
Expires: 00:01:31

And now, the BSR is SW-3 instead of SW-2, because of the highest IP address.

 

  • After a shutdown of the Loopback0 of SW-2, to simulate a problem on the RP, we can see on SW-4 we still receive the multicast stream and the RP is now: 3.3.3.3:
SW-4#show ip pim rp mapping 
PIM Group-to-RP Mappings

Group(s) 233.1.2.3/32
RP 3.3.3.3 (?), v2
Info source: 3.3.3.3 (?), via bootstrap, priority 100, holdtime 150
Uptime: 00:12:37, expires: 00:01:42
!
SW-4#show ip pim rp
Group: 233.1.2.3, RP: 3.3.3.3, v2, uptime 00:12:39, expires 00:01:40
!
SW-4#show ip mroute count 
Use "show ip mfib count" to get better response time for a large number of mroutes.

IP Multicast Statistics
3 routes using 1544 bytes of memory
2 groups, 0.50 average sources per group
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 233.1.2.3, Source count: 1, Packets forwarded: 189159, Packets received: 189162
  RP-tree: Forwarding: 2/0/0/0, Other: 2/0/0
  Source: 10.10.10.10/32, Forwarding: 189157/143/345/393, Other: 189160/1/2

As we can see, we can create RP redundancy with BSR.

 

Troubleshooting

Most of the troubleshooting and debugging methods are similar as the multicast lab-1. Please refer to the multicast lab-1.

 

 

Others posts of this series

 


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