2013年7月16日星期二

OSPF Multicast address

Question:

I was doing a small OSPF Lab Cisco 3560X Price in GNS3 with three routers in a single broadcast domain R1 (Router id 1.1.1.1 )is Drother, R2(2.2.2.2) is BDR and R3(3.3.3.3) is DR.

Now what i know is DR will lisen to Multicast IP 224.0.0.6 and will send the updates to others on Multicast IP 224.0.0.5

But my output is wierd when iam lloking in to ospf debug packets in R1 (DROTHER)

It is sending hello on 224.0.0.5 I am unable to get it. Somebody out there can u help me better understand this

R1#debug ip ospf events
R1#
*Mar  1 00:28:46.891: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:28:48.579: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:28:48.583: OSPF: End of hello processing
R1#
*Mar  1 00:28:53.467: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:28:53.471: OSPF: End of hello processing
R1#
*Mar  1 00:28:56.103: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:28:58.071: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:28:58.075: OSPF: End of hello processing
R1#
*Mar  1 00:29:02.615: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:02.619: OSPF: End of hello processing
R1#
*Mar  1 00:29:05.867: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:29:07.435: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:29:07.439: OSPF: End of hello processing
R1#
*Mar  1 00:29:12.267: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:12.267: OSPF: End of hello processing
R1#
*Mar  1 00:29:15.039: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:29:17.371: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:29:17.375: OSPF: End of hello processing
R1#
*Mar  1 00:29:21.711: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:21.715: OSPF: End of hello processing
R1#
*Mar  1 00:29:24.227: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:29:26.767: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:29:26.771: OSPF: End of hello processing
R1#
*Mar  1 00:29:31.291: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:31.295: OSPF: End of hello processing
R1#
*Mar  1 00:29:33.563: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:29:35.911: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:29:35.911: OSPF: End of hello processing
R1#
*Mar  1 00:29:40.799: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:40.803: OSPF: End of hello processing
R1#
*Mar  1 00:29:42.587: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:29:45.007: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:29:45.011: OSPF: End of hello processing
R1#
*Mar  1 00:29:50.411: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:50.415: OSPF: End of hello processing
R1#
*Mar  1 00:29:52.191: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:29:54.067: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:29:54.071: OSPF: End of hello processing
R1#
*Mar  1 00:29:59.847: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:29:59.851: OSPF: End of hello processing
R1#
*Mar  1 00:30:01.271: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:30:03.279: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:30:03.283: OSPF: End of hello processing
R1#
*Mar  1 00:30:09.591: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:30:09.595: OSPF: End of hello processing
R1#
*Mar  1 00:30:11.003: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:30:13.079: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:30:13.083: OSPF: End of hello processing
R1#
*Mar  1 00:30:19.259: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:30:19.263: OSPF: End of hello processing
*Mar  1 00:30:20.107: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:30:22.539: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:30:22.543: OSPF: End of hello processing
R1#
*Mar  1 00:30:29.103: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:30:29.107: OSPF: End of hello processing
*Mar  1 00:30:29.471: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#
*Mar  1 00:30:32.323: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:30:32.327: OSPF: End of hello processing
R1#
*Mar  1 00:30:38.679: OSPF: Rcv hello from 3.3.3.3 area 0 from FastEthernet0/0 132.1.1.3
*Mar  1 00:30:38.683: OSPF: End of hello processing
*Mar  1 00:30:38.703: OSPF: Send hello to 224.0.0.5 area 0 on FastEthernet0/0 from 132.1.1.1
R1#u
*Mar  1 00:30:42.199: OSPF: Rcv hello from 2.2.2.2 area 0 from FastEthernet0/0 132.1.1.2
*Mar  1 00:30:42.203: OSPF: End of hello processing
R1#u all
All possible debugging has been turned off
R1#sh ip ospf ne
R1#sh ip ospf neighbor
Neighbor ID     Pri   State           Dead Time   Address         Interface
2.2.2.2           1   FULL/BDR        00:00:38    132.1.1.2       FastEthernet0/0
3.3.3.3           1   FULL/DR         00:00:35    132.1.1.3       FastEthernet0/0

Regards
Thanveer
"Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."     

Answer:

I'm not sure if there's any  OSPF debug command that shows the AllDRouter address in it's output.
But since it's gns3 and not a production network we can use debug ip packets:

R1(config)#access-list 100 permit ip any host 224.0.0.6
R1#debug ip packet 100
R1#debug ip ospf adj

Now we could wait for reliable flooding or just create a new OSPF link to trigger an update.

*Mar  1 00:40:34.211: OSPF: Interface Loopback0 going Up
*Mar  1 00:40:34.711: IP: s=132.1.1.1 (local), d=224.0.0.6 (FastEthernet0/0), len 96, sending broad/multicast
*Mar  1 00:40:34.715: OSPF: Build router LSA for area 0, router ID 1.1.1.1, seq 0x80000004
*Mar  1 00:40:34.779: OSPF: Rcv LS UPD from 3.3.3.3 on FastEthernet0/0 length 76 LSA count 1
*Mar  1 00:40:42.371: OSPF: Rcv LS UPD from 3.3.3.3 on FastEthernet0/0 length 64 LSA count 1
*Mar  1 00:40:44.875: IP: s=132.1.1.1 (local), d=224.0.0.6 (FastEthernet0/0), len 64, sending broad/multicast


Another way with gns3 is Cisco 3560X  to use Wireshark.

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