Subject: DVMRP routing loop

From: Petri Helenius <[email-masked]>
Date: Tue, 7 Jan 1997 17:35:56 +0200 (EET)

There seems to be a routing loop going on somewhere in the MBone,
since after withdrawing a specific route it keeps echoing back, every
time with two to four worse metric and also another route is echoing
back with varying metrics:
fi-gw#sh ip dvmrp route reggae-str.ml.tele.fi.
DVMRP Routing Table - 4168 entries
193.167.64.0/23 [0/24] uptime 00:03:26, expires 00:00:33
    via 193.166.2.225, Tunnel0, [version mrouted 3.8] [flags: GPM]
fi-gw#sh ip dvmrp route reggae-str.ml.tele.fi.
DVMRP Routing Table - 4062 entries
193.167.64.0/23 [0/26] uptime 00:00:16, expires 00:02:43
    via 193.166.2.225, Tunnel0, [version mrouted 3.8] [flags: GPM]
fi-gw#sh ip dvmrp route reggae-str.ml.tele.fi.
DVMRP Routing Table - 4185 entries
193.167.64.0/23 [0/28] uptime 00:01:42, expires 00:02:18
    via 193.166.2.225, Tunnel0, [version mrouted 3.8] [flags: GPM]

fi-gw#sh ip dvmrp route reggae-str.ml.tele.fi.
DVMRP Routing Table - 4187 entries
193.166.0.0/15 [0/14] uptime 00:12:41, expires 00:02:31
    via 193.166.2.225, Tunnel0, [version mrouted 3.8] [flags: GPM]

It also seems that the number of routes is on the MBone is on the high
side. (somebody redistributing unicast routes but hitting into the
built-in limit now?)

Pete

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From: Toerless Eckert <[email-masked]>
Date: Tue, 7 Jan 1997 16:39:09 +0100 (MET)

Question:

We are experiencing packet duplication on mbone between the win (german
university part on mbone)  and ebone sites. Can this be caused by the
problem you describe, pete ?

Toerless

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From: Petri Helenius <[email-masked]>
Date: Tue, 7 Jan 1997 17:52:22 +0200 (EET)

> problem you describe, pete ?
That is very likely. Can do you a
mtrace reggae-str.ml.tele.fi 224.42.42.2

, please?

Pete

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From: Bill Fenner <[email-masked]>
Date: Tue, 7 Jan 1997 08:27:58 PST

Speaking of duplicates, I'm seeing duplicate packets yet again between
upper-gw and lower-gw.  This pair of routers seem to periodically get
into a state where they create lots and lots of duplicates (in this
particular case it's only 14 copies of each packet).

  Source        Response Dest    Overall     Packet Statistics For Traffic From
130.240.34.6    224.0.1.32       Packet      130.240.34.6 To 224.2.0.1
     |       __/  rtt  416 ms     Rate       Lost/Sent = Pct  Rate
     v      /     hop -204 s     -------     ---------------------
...
193.10.80.33    upper-gw.sunet.se 
     |     ^      ttl   19        57 pps      -26/2    = --%   0 pps
     v     |      hop  156 ms
193.10.80.34   
192.36.148.197  lower-gw.sunet.se 

Can someone please look into this?

Thanks,
  Bill

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From: Bjorn Carlsson <[email-masked]>
Date: Tue, 07 Jan 97 20:29:40 +0100

Well, I removed decnet from these boxes earlier tonight, maybe something got
screwed up then. I've been checking with tcpdump on stockholm.mbone.ebone.net
and can see no duplicates from 130.240.34.6 now atleast. 

stockholm# ./tcpdump -e -l -v -i le1 -n src host 130.240.34.6
tcpdump: listening on le1
20:23:17.954204 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 146: 130.240.34.6.33061 > 224.2.0.1.23457: udp 104 (ttl 186, id 38193)
20:23:21.468933 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38194)
20:23:24.314457 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 110: 130.240.34.6.33061 > 224.2.0.1.23457: udp 68 (ttl 186, id 38195)
20:23:28.965373 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38197)
20:23:34.428326 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 146: 130.240.34.6.33061 > 224.2.0.1.23457: udp 104 (ttl 186, id 38198)
20:23:38.508375 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38199)
20:23:45.321992 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38200)
20:23:49.478557 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38201)
20:23:52.179763 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 146: 130.240.34.6.33061 > 224.2.0.1.23457: udp 104 (ttl 186, id 38202)
20:23:58.348567 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38203)
20:24:05.229872 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 110: 130.240.34.6.33061 > 224.2.0.1.23457: udp 68 (ttl 186, id 38204)
20:24:10.217385 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38205)
20:24:17.343851 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 146: 130.240.34.6.33061 > 224.2.0.1.23457: udp 104 (ttl 186, id 38206)
20:24:23.646234 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38207)
20:24:26.677515 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38208)
20:24:31.827983 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38209)
20:24:38.607243 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 146: 130.240.34.6.33061 > 224.2.0.1.23457: udp 104 (ttl 186, id 38211)
20:24:42.006846 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38212)
20:24:49.165868 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 110: 130.240.34.6.33061 > 224.2.0.1.23457: udp 68 (ttl 186, id 38213)
20:24:53.445099 0:0:c:13:6e:6c 1:0:5e:2:0:1 0800 142: 130.240.34.6.33061 > 224.2.0.1.23457: udp 100 (ttl 186, id 38214)

--BC

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From: Dino Farinacci <[email-masked]>
Date: Tue, 7 Jan 1997 11:43:20 -0800

>> and can see no duplicates from 130.240.34.6 now atleast. 

    Bjorn, turn off multicast fastswitching and then do "debug ip mp <group>
    detail". It will give layer-2 MAC level information so you can tell who 
    (plural) is forwarding the packet on the Ether.

Dino