[c-nsp] crs-1 ISSU?

Richard Gallagher rgallagh at cisco.com
Wed May 13 10:53:59 EDT 2009

The only answer without more info is "it depends" unfortunately.

What release are you upgrading from and going to?

I'd start with the upgrade guides here:



On 12 May 2009, at 17:41, Marlon Duksa wrote:

> Hi,Can anyone point me to the documentation where it says that Cisco  
> on CRS-1 supports a true  in-service-software-upgrades (ISSU)?
> I've been looking on CCO but all they talk in IOS XR is ISSU where  
> they
> patch a code and things like that.
> What I'm looking is to upgrade a CRS-1 to a new software image with a
> subsecond outage. This means upgrading the control plane and line  
> cards with
> the new software images with subsecond outage. Not just a specific  
> software
> module or a line card but the whole system to upgrade between two  
> major
> releases.
> I assume that non stop routing (not forwarding) would be a  
> prerequisite for
> this, but it seams that they support NSR only for ISIS. NSR implies
> statefull failover where all protocol states/transactions are  
> mirrored and
> synched between two routing engines. For example, BGP TCP sessions  
> stays the
> same during the routing engine failover.
> Thanks,
> Marlon
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