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New Member

Multicast streaming only works for 255 secondsm but wait there is more....

Good Morning,

We suddenly started having problems multicasting from our Internet2 connection last month, In the past two weeks we have had two conference calls with Cisco TAC totaling 9 hours. We have them stumped so far.

The problem we have is we can only stream videos for a short period and then they just stop working. On our first call with TAC they determined if I do a "clear ip igmp group" I can stream again for a short period. Just clearing igmp for the source stream doesn't help we have to do all the igmp groups.

This morning it occured to me (and I don't know why we didn't think of this sooner) is to clock exactly how long I can play a multicast stream. What I found suprised me.

Multicast streaming stops working 255 seconds after I last clear the IGMP tables. This is significant because as I understand it 255 is the default time to live for multicast traffic. I did the test multiple times running a stopwatch and the results are the same every single time.

If I clear the IGMP tables and wait 195 second before streaming I only get 60 second of streaming. So it is not that clearing the tables lets me stream for 255 seconds whenever I choose but rather my window for streaming anything is 255 seconds from the time I clear the table, period.

Any thoughts!!

Thank You,



Re: Multicast streaming only works for 255 secondsm but wait the


Have you done a packet capture to see if your are seeing igmp join/leave messages?

Also have you tried using static igmp join ie

ip igmp static-group

This may help you narrow down if it's a client issue or further upstream.


New Member

Re: Multicast streaming only works for 255 secondsm but wait the

Thanks for thre quick reply James.

The static IGMP join gives the same results.. video only plays for 255 seconds. I just tried it again.

Regarding the packet capture... I don't remember for certain but I don't *think* we were getting leave requests once the 255 seconds hit.



Hall of Fame Super Silver

Re: Multicast streaming only works for 255 secondsm but wait the

Hello Joe,

the TTL is expressed in router hops only in the early days it was thought to be a time measure.

However, as already suggested you need to understand where the process fails:

if there is a missing of IGMP reports from receivers.

if it is the PIM join to the upstream router to be missing.

Hope to help


New Member

Re: Multicast streaming only works for 255 secondsm but wait the


Yes I know TTL is expressed in router hops but I am just trying to figure out what else I can relate to the 255 seconds of it working. Maybe somehow the the TTL is increasing once a second... I don't know. My mutlicast threshold is set to 0 on my router so this should be ok.

Interestingly enough Cisco TAC seemed to think our our first call that Layer 2 on on metro ethernet saw the appropriate traffic but that it wasn't being communicated to layer 3 properly unless we cleared the IGMP tables.

Thanks again... will keep everyone informed.