CCIE Pursuit Blog

August 17, 2008

Internetwork Expert Volume II: Lab 8 – Section 5

Section 5 – IP Multicast – 11 Points

5.1 PIM

Basic multicast task. We are not told which PIM mode to use, but by reading ahead we can see that we’ll be using Auto-RP so we’ll need sparse-dense mode.

Sparse-Dense Mode for Auto-RP

5.2 Auto-RP

Configure r1 and r2 to use Auto-RP and announce their lo0 interfaces as candidate RP’s.

Configuring Sparse Mode with Auto-RP

“Configure r3 to map all multicast groups with an even numbered first octet to r1 and odd-numbered to r2.”

There’s no “minimal configuration” stipulation so let’s just make so basic access-lists:

r1(config)#ip access-list standard TASK_5_2_EVEN
r1(config-std-nacl)#permit 224.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 226.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 228.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 230.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 232.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 234.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 236.0.0.0 0.255.255.255
r1(config-std-nacl)#permit 238.0.0.0 0.255.255.255

r1(config)#ip pim send-rp-announce lo0 scope 16 group-list TASK_5_2_EVEN

On r3(mapping agent) you will need to apply those same ACLs and then:

r3(config)#ip pim send-rp-discovery lo0 scope 16

Now we need to set up our rp-list ACLs:

r3(config)#ip access-list standard R1_LOOP
r3(config-std-nacl)#permit 150.1.1.1
r3(config-std-nacl)#ip access-list standard R2_LOOP
r3(config-std-nacl)#permit 150.1.2.2

Finally, we set our rp-announce-filters:

r3(config)#ip pim rp-announce-filter rp-list R1_LOOP group-list TASK_5_2_EVEN
r3(config)#ip pim rp-announce-filter rp-list R2_LOOP group-list TASK_5_2_ODD

For some reason I could not get the r2 to map even though my configuration was correct and r2 saw itself elected:

r2#sh ip pim rp map
PIM Group-to-RP Mappings
This system is an RP (Auto-RP)

The problem was that there was no multicast path to r2.  I forgot to configure PIM on the Multilink interfaces on r2 and r3.  DOH!!!

5.3 Multicast Distribution

Multicast traffic should switch to a source based tree once a source is sending 128Kbps or more.

ip pim spt-threshold

r1(config)#ip pim spt-threshold 128

5.4 Multicast Testing

Users in VLAN 4 cannot receive multicast feeds from VLAN 52. 

“Configure…so that r4 responds to ICMP echo requests sent the multicast group 224.4.4.4 from VLAN 52.”

First things first:

r4(config)#int f0/0
r4(config-if)#ip igmp join-group 224.4.4.4

These VLANs are on the spokes.  PIM NBMA mode is needed on the hub.

Before:

r5#p 224.4.4.4 source 174.1.45.5

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.4.4.4, timeout is 2 seconds:
Packet sent with a source address of 174.1.45.5
.
r5#

r1(config-if)#ip pim nbma-mode
PIM nbma-mode is not recommended for sparse-dense-mode

After:

r5#p 224.4.4.4 source 174.1.45.5

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.4.4.4, timeout is 2 seconds:
Packet sent with a source address of 174.1.45.5

Reply to request 0 from 174.1.145.4, 52 ms

5.5 Broadcast Distribution

This is a common scenario in which we need to map a multicast feed to a broadcast address using the ‘ip multicast helper-map’ command.

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