[c-nsp] Cisco 7600/SUP720-3BXL SRD -> SRE => Egress -> Ingress Multicast Replication Mode

[Emanuel Popa]

On Wed, Aug 8, 2012 at 10:02 PM, John Neiberger <jneiberger at gmail.com> wrote:
> On Wed, Aug 8, 2012 at 8:41 AM, Emanuel Popa <emanuel.popa at gmail.com> wrote:
>> On Wed, Aug 8, 2012 at 5:14 PM, John Neiberger <jneiberger at gmail.com> wrote:
>>> On Wed, Aug 8, 2012 at 5:30 AM, Emanuel Popa <emanuel.popa at gmail.com> wrote:
>>>> After opening a SR for the issue below, Cisco TAC called to tell us
>>>> that SRE defaults to ingress replication without giving us any solid
>>>> reason for it. Also the TAC engineer clearly stated that we will see
>>>> no big difference between ingress and egress replication mode. He also
>>>> advised that if we really want to switch to egress replication it
>>>> would be better to do it inside a maintenance window. All of this on
>>>> the phone and nothing appears within the Service Request tool.
>>>
>>> What linecards do you have? If you're doing multicast, the linecard
>>> type is important. In many cases there can be a HUGE difference
>>> between ingress and egress replication mode.
>>>
>>> John
>>
>> Usually:
>> - WS-SUP720-3BXL or RSP720-3CXL-GE
>> - WS-X6704-10GE + WS-F6700-DFC3CXL/WS-F6700-DFC3BXL
>> - WS-X6724-SFP + WS-F6700-DFC3CXL/WS-F6700-DFC3BXL
>>
>> Manu
>
> If you have a significant amount of multicast traffic, the presence of
> the 6704 and 6724 will certainly increase the potential for
> replication problems in ingress mode. On those modules, the inbound
> Janus ASIC is responsible for all replications in ingress mode but
> that responsibility is somewhat distributed in egress mode. This is
> especially true if you have any etherchannels or SPAN ports
> configured. However, as others have said, some features don't work in
> egress mode, so it all depends on what you need your system to do.

Guys, here is the effect on the fabric of a WS-X6704-10GE linecard
with DFC after switching from ingress to egress replication mode:
http://bit.ly/ingress

We weren't expecting such a huge impact. Ingress fabric channel
utilization dropped from 40% to 25% instantly on one 20GE fabric
channel of the WS-X6704-10GE linecard.

Manu