CCIE Pursuit Blog

August 14, 2008

Internetwork Expert Volume II: Lab 12 – Section 6

Section 6 – IP Multicast – 8 Points

6.1 PIM

I doesn’t get any easier than this.  You’re asked to configure dense mode on specific interfaces.

6.2 Multicast Distribution

Users in VLAN 22 want access to a video feed on 225.25.25.25 (using UDP port 31337) from VLAN 17. For some reason (most likely because PIM is not configured on r3’s s1/3 🙂  ) r3 is not passing this traffic to r2.  Configure the network so that the users can receive traffic from this group.

“Do not enable PIM on any additional interfaces to accomplish this.”

Fuck.  There goes the easy solution.

This has me stumped.  The multicast path from VLAN 17 to VLAN 12 is broken at r3. Is there a way to change this traffic to unicast or broadcast traffic?  Yup.  🙂

ip multicast helper-map

To allow IP multicast routing in a multicast-capable internetwork between two broadcast-only internetworks, use the ip multicast helper-map command in interface configuration mode.

Configuring an Intermediate IP Multicast Helper Between Broadcast-Only Networks

r3:

Rack16R3(config)#ip access-list ex TASK_6_2
Rack16R3(config-ext-nacl)#permit udp any any eq 31337
Rack16R3(config)#ip forward-protocol udp 31337

Rack16R3(config)#int s1/3
Rack16R3(config-if)#ip directed-broadcast

Rack16R3(config)int s1/2
Rack16R3(config-if)ip multicast helper-map 225.25.25.25 129.16.23.255 TASK_6_2

r2:

Rack16R2(config)#ip forward-protocol udp 31337
Rack16R2(config)#ip access-list ex TASK_6_2
Rack16R2(config-ext-nacl)#permit udp any any eq 31337

Rack16R2(config-ext-nacl)#int s0/1
Rack16R2(config-if)#ip multicast helper-map broadcast 225.25.25.25 TASK_6_2

There are a lot of verification commands in the solution guide, but nothing as far a breakdown.

6.3 Static RP

Well you didn’t think that we were going to get away with just running dense-mode on three devices did you?  This task has you set up a pim-spare multicast network in the OSPF half of the network.

The weird bit is that we have to create loopback 1 on r4 and r5 and then give them the same address and advertise them into OSPF.

Then we need to configure r6 to use r4’s loopback 1 as the RP and sw2 to use r5’s loopback 1 as the RP.  If either should fail, then they should switch over to the other loopback 1 as the RP.  Remember, these loopbacks have the same /32 address.

Enter a command I’ve never heard of before”

ip msdp peer

To configure a Multicast Source Discovery Protocol (MSDP) peer, use the ip msdp peer command in global configuration mode.

Rack16R5(config)#ip msdp peer 150.16.4.4 connect-source lo0
Rack16R4(config)#ip msdp peer 150.16.5.5 connect-source lo0

Aug 12 14:05:14.346: %MSDP-5-PEER_UPDOWN: Session to peer 150.16.5.5 going up

After that bit is configured, just statically map your RP’s on r6 and sw2:

Rack16R6(config)#ip pim rp-address 150.16.0.255
Rack16SW2(config)#ip pim rp-address 150.16.0.255

Rack16R4#sh ip msdp peer
MSDP Peer 150.16.5.5 (?), AS 100
  Connection status:
    State: Up, Resets: 0, Connection source: Loopback0 (150.16.4.4)
    Uptime(Downtime): 00:00:37, Messages sent/received: 0/1
    Output messages discarded: 0
    Connection and counters cleared 00:00:37 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
  Input queue size: 0, Output queue size: 0

Rack16R4#sh ip msdp summary
MSDP Peer Status Summary
Peer Address     AS    State    Uptime/  Reset SA    Peer Name
                                Downtime Count Count
150.16.5.5       100   Up       00:01:05 0     0     ?

Rack16R6#sh ip pim rp map
PIM Group-to-RP Mappings

Group(s): 224.0.0.0/4, Static
    RP: 150.16.0.255 (?)

Rack16SW2#sh ip pim rp mapp
PIM Group-to-RP Mappings

Group(s): 224.0.0.0/4, Static
    RP: 150.16.0.255 (?)

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