[c-nsp] Multicast issues on 7600s with WS-6748-sfp blades

[Matthew Huff]

I have seen some pretty low level problems with multicast packets being dropped on the floor by the hardware forwarded on 67xx linecards. The bug seems to appear when changes that effect the asic (turning on "mls qos" for example). Resetting the sup engine doesn't resolve it. Everything looks good at the CEF/mfib level, and all counters show the packet count increasing, but the packets never get forwarded out of the linecard.

Cisco engineering was able to verify this was happening, but had no solution other than resetting the linecard. Once it was reset, everything worked.

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Matthew Huff       | One Manhattanville Rd
OTA Management LLC | Purchase, NY 10577
http://www.ox.com  | Phone: 914-460-4039
aim: matthewbhuff  | Fax:   914-460-4139


> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of John
> Neiberger
> Sent: Wednesday, July 28, 2010 6:04 PM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Multicast issues on 7600s with WS-6748-sfp blades
> 
> We have a weird problem on some 7606s with WS-6748-SFP blades. We have
> a whole bunch of multicast streams running through these routers and
> there are multicast receivers directly attached. We had a problem
> where one particular multicast stream would occasionally have dropped
> packets resulting in MPEG CC errors on the receiver. We were able to
> prove that the source was clean, as were the paths between the source
> and the receiver. The receiver was not seeing MPEG CC errors on any
> other stream, which is really odd.
> 
> Here's where it gets even stranger. When we moved the receiver to
> another port, like from 23 to 24, the receiver still saw the errors.
> We moved it to port 25 and the errors apparently went away. Our only
> guess is that this could potentially be an issue with the ASICs on the
> blade. Ports 13-24 are controlled by one ASIC (I believe a Rohini
> ASIC), and the four Rohini ASICs connect to two Janus ASICs. That is
> as I understand it. I may be wrong. When we moved the receiver from
> port 24 to 25, we moved to a different Rohini ASIC and possibly to
> another Janus ASIC. Regardless, according to our video guys the
> problem cleared up after the move.
> 
> Have any of you ever experienced anything like this? Could this really
> be a problem on the Rohini or Janus ASICs? What sort of problem would
> only affect certain multicast groups and not others?
> 
> Thanks
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