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

Emanuel Popa emanuel.popa at gmail.com
Wed Aug 8 07:30:55 EDT 2012

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.


On Mon, Aug 6, 2012 at 11:00 AM, Emanuel Popa <emanuel.popa at gmail.com> wrote:
> On Fri, Aug 3, 2012 at 4:05 PM, Phil Mayers <p.mayers at imperial.ac.uk> wrote:
>> On 03/08/12 12:54, Emanuel Popa wrote:
>>> Hi there,
>>> A while ago we upgraded our 7600 Cisco boxes with SUP720-3BXL and LAN
>>> cards from SRD to SRE IOS version. After successfully upgrading all
>> Some features are incompatible with egress mode. It's possible that the IOS
>> upgrade introduced more checks and/or forced ingress mode as problems were
>> found
>> For example, MVPN needs ingress mode, and IIRC QoS and SPAN have problems
>> with egress mode.
>>> boxes we noticed at least a strange behavior: all Cisco 7600 boxes had
>>> "mls ip multicast replication-mode ingress" as an extra command in
>>> their running configuration file. Before upgrading, all boxes were
>>> doing egress replication for multicast traffic. And it seems they are
>> Are you sure? You checked this with the "sh platform" command?
> I'm pretty sure. We spent quite some time with our multicast setup in
> the past to understand the difference between the P and the PE routers
> when it comes to MVPN. Because of the ingress replication mode on the
> PE routers we installed dedicated PE routers for the MVPN traffic.
> This way we manged to keep egress replication mode on every other
> router in the network.
>>> still able to do it:
>>> #show platform software multicast ip capability
>> What happens if you "no" the command and let it go back to auto-detect mode?
> When you "no" that command the router simply moves from auto-detection
> OFF to auto-detection ON and replication mode switches from ingress to
> egress.

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