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

[John Neiberger]

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.