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

[John Neiberger]

It is a DFC card. We have a TAC case open about this, but we have
instances of weirdness happening on another device recently that is
similar and we haven't opened a TAC case yet on that one. I wonder if
we're running into an issue with the Janus ASIC. That has been
suggested by some people here, but others were waiting for Cisco TAC
to confirm it.

On Thu, Jul 29, 2010 at 9:00 AM, Benjamin Lovell <belovell at cisco.com> wrote:
> John,
>
> Is your 6748 a DFC line card? If so you are correct, moving from port 24 to 25 would have moved you to the other Janus ASIC. Janus is the fabric/mcast replication ASIC.
>
> If your problem is ONLY with mcast then you can safely ignore the Rohini. We have addressed a number of issues with mcast replication on the Janus in recent years. So if you are running older 12.2(18)SXF or even earlier SX code you may want to consider an IOS update. Also not knowing your network I can't say but it's not impossible to hit the scale limits with high rates mcast pps and mroute counts.
>
> The newer LCs with the 3CXL use a newer replication ASIC that preforms significantly better than the Janus.
>
>
> -Ben
>
>
> On Jul 28, 2010, at 6:04 PM, John Neiberger wrote:
>
>> 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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>