Re: TCP Error

On 12-Mar-2012 13:36 , Victor Hunt wrote:

I am seeing error message TCP26A2 appear in the qsysopr message queue
with some frequency. It tells me that a "Source specific multicast
error occurred". I then goes on to say that "The network will be
operating in compatibility mode, which prevents source filtering."

While I understand the concept of multicast, this error message
doesn't give me much to work on. A search on Google returns a couple
of pages mostly related to PTFs describing conditions when this error
does not display. A search of IBM's software and hardware pages
returns no hits at all for TCP26A2.
<<SNIP>>

A web search also reveals at least one APAR with that the error message [though not in symptom keyword form msgTCP26A2], describing a condition where that error message is reported repeatedly:
_MA41438 - LIC-COMM-TCPIP REPEATED TCP26A2 SSM ERROR MESSAGES RECEIVED_
http://www.ibm.com/support/docview.wss?uid=nas2a7cd68b75c02563886257919003c7a2d
"
Software version(s): V6R1M0, V6R1M1, V7R1M0
_Problem Summary_
Message TCP26A2 (Source specific multicast error occurred) is
issued repeatedly for the same line.
_Problem Conclusion_
An older version IGMP or MLD querier exists on the network. When
an older IGMP/MLD query is received by the system, a timer is
started but due to a race condition, the system may start
multiple timers. This can result in the system prematurely
leaving the IGMP/MLD mode compatible with the router and so
repeatedly switching between IGMP version 3 or MLD version 2 and
compatibility mode. The TCP26A2 message is issued each time the
switch to compatibility mode occurs.

The race condition has been resolved so that the system will not
prematurely switch back to IGMPv3/MLDv2 modes. This should
eliminate the repeated messages."

Regards, Chuck