Multicast forwarding loop at mbone-cern.switch.ch

[Bill Fenner <]

Hi,

  There's a pretty bad forwarding loop at mbone-cern.switch.ch:

  Source        Response Dest    Overall     Packet Statistics For Traffic From
130.59.4.22     224.0.1.32       Packet      130.59.4.22 To 224.2.200.165
     |       __/  rtt  795 ms     Rate       Lost/Sent = Pct  Rate
     v      /     hop    0 ms    -------     ---------------------
130.59.4.22     nuptse.switch.ch 
     |     ^      ttl   17         1 pps        0/2    = --    0 pps
     v     |      hop    0 ms      1 pps        0/4    = --    0 pps
130.59.20.50    mbone-zh.switch.ch 
     |     ^      ttl   34         1 pps        0/2    = --    0 pps
     v     |      hop    0 ms      1 pps     -157/4    = --    0 pps
192.65.185.100  mbone-cern.switch.ch 

This is probably the Solaris+IOS bug described at
http://sandbox.parc.xerox.com/fenner/mcast/flooding.html .

The TTL's I'm observing appear to be symptomatic of multiple interacting
loops.  I don't know the topology well enough to say who's misbehaving
for sure, but if either all of mbone-cern.switch.ch's IOS neighbors
are upgraded to a version of IOS that implements "DVMRP conditional
flooding", or if mbone-cern gets the fixed multicast kernel patches,
the problem should go away.

Thanks,
  Bill