From: gladston@br.ibm.com
Date: Mon Nov 29 2004 - 18:12:52 GMT-3
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.
This archive was generated by hypermail 2.1.4 : Thu Dec 02 2004 - 06:57:51 GMT-3