Multicast Duplicate Packets

[agnewa]

I'm currently experiencing issues with duplicate packets on our multicast network. It's a pretty simple configuration - sparse-mode only with a static RP.  The multicast sender is connected to a Cisco 6509 switch. 

I've taken a wireshark trace and it appears that the 6509 is actually generating the duplicate packets.  I'd be interested to know if anyone experienced symptoms like this before or can offer any configuration / troubleshooting hints.

[Joseph W. Doherty]

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Posting

Are you sure the duplicates aren't from shared tree to source tree switch over?

[agnewa]

Joseph - apologies but i'm not sure how to confirm that.  Anything you could advise?

When the sender server port is opened we see single multicast packets on the 6509 but after around maybe 10 seconds they start becoming duplicates and carry on like that until the server port is shutdown.

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

From one of your later posts, I see you note the duplicates are continuous.  What I'm describing should be temporary.

[lorricklee]

Hi,

Does it happen every time a timer goes off ?
Any other multicast routers nearby ?

Sent from Cisco Technical Support iPad App

[agnewa]

The multicast sender server is connected to a 6509 that is also connected to multiple other Cisco devices for redundancy.  I have attempted to simplify the configuration by only have PIM enabled on a single path from sender to receiver. 

The receivers are on different areas of the network but I'm seeing the duplicates on the port connected to the sender.  All these duplicate packets are then transmitted to the receiver LAN's.

I also have a single statically assigned RP that is also connected to the sender 6509 (albeit on a different LAN).  The RP configuration is restricted to certain groups via an access-list.

When the sender server port is opened it starts with single packets but after a very short time (maybe 10 secs) it starts sending duplicate packets continually.