[c-nsp] Warm reload in Cisco 6500

[Christophe Fillot]

Keegan Holley wrote:
> Is traffic still forwarded during the reload?  It's not explicitly mentioned
> whether or not the reload is control plane only.
>   
The "reload warm" command is not available on 12.2(33)SXI4a for sure
(I've just checked it).

The warm reload feature works by loading and uncompressing the new
image before rebooting. The current IOS image is still running and
forwarding traffic during this phase. When the device reboots, it skips
the flash reading step since the new IOS is already present in memory
(of course, the device doesn't forward traffic during this).
Note that you have to configure "warm-reboot" and reboot to enable
the feature (it has to reserve some memory iirc).


>
> On Mon, Jan 3, 2011 at 5:44 PM, Phil Mayers <p.mayers at imperial.ac.uk> wrote:
>
>   
>> On 01/03/2011 12:04 PM, Grzegorz Janoszka wrote:
>>
>>     
>>> There is a nice feature in Cisco IOS:
>>>
>>> http://www.cisco.com/en/US/docs/ios/fundamentals/configuration/guide/warm_reload.html
>>>
>>> According to Cisco software advisor (Find software with the features I
>>> need), it is available in 12.2 for C6500/SUP720 in all releases of
>>> trains SXH and SXI.
>>>
>>>       
>> I think software advisor is incorrect (big surprise). Warm Reload is not
>> available on this platform I'm pretty sure.
>>
>> If you have two supervisors you can "emulate" it with RPR+ mode. However
>> when you force a switchover you still have 30-90 seconds of outage as your
>> linecards reload, dependent on your linecard mix and configured features.
>>
>> There is also eFSU in later versions of IOS, giving 0-3 seconds outage if
>> you have enough RAM on the linecards, but I'm not sure if you could (ab)use
>> that to reload into the same IOS version; the argument to "issu loadversion"
>> probably needs to be a different IOS than the running one?
>>
>> And of course both involve the expense of a 2nd SUP, which is why Cisco
>> aren't incentivised to implement warm reload - their way, you spend more
>> money!
>>
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>>     
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