From: McCallum, Robert (robert.mccallum@thus.net)
Date: Tue Nov 30 2004 - 12:21:47 GMT-3
the assert winner is usually chosen on the highest loopback address.
Robert McCallum
CCIE #8757 R&S
> -----Original Message-----
> From: gladston@br.ibm.com [mailto:gladston@br.ibm.com]
> Sent: 29 November 2004 21:13
> To: ccielab@groupstudy.com
> Subject: Assert Message
>
>
> Williamson Multicast book (great book) shows on page 537:
> " This message is used in both dense mode and sparse mode
> PIM" It is refering to Assert Messages.
>
> Based on this, I tried to influence what router forwards the
> multicast to a multiaccess segment but the result were not
> the expected. Any comments appreciated
>
> R1-R3-R6 are connected to the multicast segment. R4 is the
> router connected to the source, forwarding to group
> 239.5.5.5. R1-R4 and R3-R4 are serial links. The metric of
> the serial links was manipulated trying to get the multicast
> forwarded by R1.
>
> The results shows that the metric doesn't matter; what
> matters is the DR. If R1 is the DR, R1 forwards multicast to
> the multiaccess segment. If R3 is the DR, R3 forwards
> multicast to the multiaccess segment.
>
> The commands:
>
> r1#sir 172.16.45.7
> Routing entry for 172.16.45.0/24
> Known via "ospf 1", distance 110, metric 58, type intra area
> Last update from 172.16.14.4 on Serial0/0.14, 00:03:44 ago
> Routing Descriptor Blocks:
> * 172.16.14.4, from 172.16.70.7, 00:03:44 ago, via Serial0/0.14
> Route metric is 58, traffic share count is 1
>
> r3#sir 172.16.45.7
> Routing entry for 172.16.45.0/24
> Known via "ospf 1", distance 110, metric 110, type intra area
> Last update from 172.16.34.4 on Serial0.34, 00:03:26 ago
> Routing Descriptor Blocks:
> * 172.16.34.4, from 172.16.70.7, 00:03:26 ago, via Serial0.34
> Route metric is 110, traffic share count is 1
>
> r3#sh ip pim int
>
> Address Interface Ver/ Nbr Query
> DR DR
> Mode Count Intvl Prior
> 172.16.16.33 Ethernet0 v2/SD 2 30
> 1 172.16.16.33
>
>
> r3#sh ip mrout 239.5.5.5
> (*, 239.5.5.5), 01:02:09/00:02:59, RP 172.16.2.1, flags: SJC
> Incoming interface: Serial0.32, RPF nbr 172.16.23.2
> Outgoing interface list:
> Ethernet0, Forward/Sparse-Dense, 00:01:34/00:02:54
>
> (172.16.45.7, 239.5.5.5), 00:01:28/00:02:59, flags: CT
> Incoming interface: Serial0.34, RPF nbr 172.16.34.4
> Outgoing interface list:
> Ethernet0, Forward/Sparse-Dense, 00:00:05/00:02:54
> Serial0.32, Forward/Sparse-Dense, 00:01:13/00:02:47
>
> r1#sh ip mrou 239.5.5.5
> (*, 239.5.5.5), 01:03:40/00:02:59, RP 172.16.2.1, flags: SJP
> Incoming interface: Serial0/0.12, RPF nbr 172.16.112.2
> Outgoing interface list: Null
>
> (172.16.45.7, 239.5.5.5), 00:52:02/00:00:56, flags: PJT
> Incoming interface: Serial0/0.14, RPF nbr 172.16.14.4
> Outgoing interface list: Null
>
>
> If I swap the metric (R1 being the DR with worse cost to R4),
> R1 start to forward traffic to the multiaccess network.
>
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