[c-nsp] In Service Software Upgrade

[Aleksandr Gurbo]

Hello,

I want upgrade IOS on the cisco 7600 with two Sup32 without rebooting. I use for this ISSU procedure.
I try migrate from SRC to SRD branch. IOS is upgraded, but downtime duration is about 280 seconds. All sessions(ospf, mpls, bgp) with neighbors was lost. NSF and GR(for mpls,ospf,bgp) are turned on.
In ISSU process I saw that c7600 has switched from SSO to RPR mode. All interface cards have been reloaded. I thought that the problem in IOS, because I use different branches of IOS(SRC->SRD3). For the test, I tried to switch from SRD2 to SRD3 - the result is the same. 	
I think the problem is in the switching mode(from SSO to RPR).

How to upgrade IOS without downtime?

-- 
Aleksandr Gurbo