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Twinkie
Posts: 20
Registered: ‎04-07-2011
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Accepted Solution

VC fail over - how long?

Hello,

We are fairly sure there is something wrong with our existing Master switch.  I would like to issues the command "request chassis routing-engine master switch" but we are also in a live, high production enviroment.  How long will the network drop for?  This is two EX4200 in a VC acting as our network core.  We also run 24x7 so downtime is not easy to find.

 

Note I will be chaning the current master priority from 255 to 128 so that it matches the second switch in the VC shortly as well.

 

Any feedback appriciated.

Thanks.

Recognized Expert
wimclend
Posts: 272
Registered: ‎04-03-2009

Re: VC fail over - how long?

depends on a couple of factors --

 

1)  are you using the built-in VCP cables, or extended via fiber?

 

2)  is the VC layer-2 only, or performing layer 3 functions as well?

 

3)  what version of code are you running?  newer versions have added NSR and NSB which will greatly affect the downtime (should be next to none with these running)

 

if its layer 2 only then downtime should be very brief -- if STP is in use it will have to recalculate though (unless NSB is being used).  if its also functioning as a router, and NSR is not being used, then routing adjacencies will bounce, so convergence really depends on what protocols you are using.

 

Will

Recognized Expert
wimclend
Posts: 272
Registered: ‎04-03-2009
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Re: VC fail over - how long?

also I forgot to add -- make sure you have GRES configured regardless, otherwise downtime will be way longer as the line-card switches have to reconnect to the new master, relearn MACs, etc.

 

will

Contributor
Twinkie
Posts: 20
Registered: ‎04-07-2011
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Re: VC fail over - how long?

Thanks for the Reply.  We are using 10.4R4.5 and they are setup as layer 3.  Graceful failover is enabled.  The backup is where most everything is plugged into anyway.

Contributor
Twinkie
Posts: 20
Registered: ‎04-07-2011
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Re: VC fail over - how long?

Oh yeah, and we are using 10GB fiber, not the supplied VC cables.

Recognized Expert
wimclend
Posts: 272
Registered: ‎04-03-2009

Re: VC fail over - how long?

in theory I believe if you have graceful restart enabled and all of the surrounding routers support it and have it enabled, traffic loss should be very small.  I do not have much experience with graceful restart, however, so can't really comment.  and I think enabling requires an adjacency reset (may be protocol specific, not sure)/

 

at any rate, I would say to be safe expect however much time it would take if you were to just reset all of your routing adjacencies on the VC, as that is what will happen when the routing engines flip, since RPD will have to restart on the new master.

 

good luck!

 

will

Contributor
Twinkie
Posts: 20
Registered: ‎04-07-2011
0

Re: VC fail over - how long?

Thanks,

Made the change last night at 0'Dark thirty.  Only lost two pings.  Now I can breathe again... 

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