[nsp] Graceful shutdown

[Stephen J. Wilcox]

On Tue, 6 Jul 2004, sam_ml at spacething.org wrote:

> Hi,
> 
> I've been thinking about some expect scripts that would shut a router down
> gracefully (ie. without packet loss), by giving backup routers time to
> takeover traffic forwarding before the power cycle.
> 
> The existing configuraion would be saved, and then an expect script would
> modify it to effectively make _it_ the backup router, then reboot it some
> time later - say 120 seconds - without saving the modifications.
> 
> For HRSP/VRSP you could lower the priority of each of the groups to below
> that of a pre-empting backup router. For BGP sessions configuring
> "prefix-list none in"/"prefix list none out"  for every peer should give
> BGP time to converge before the router reboots.
> 
> It might also be possible to do this with some Layer2 ethernet devices by
> raising the spanning-tree cost of every port in an attempt to deflect
> traffic away from it.
> 
> Does this seem reasonable? Does something like this already exist, or 
> should I get out my expect hat?

ive tried to do graceful shuts during maintenance, the problem i've had is that 
the changes that are made locally stop the local router but remote routers 
require hold timers etc to expire creating an issue where there are packets 
coming in but theres no paths to get out

this applies to stp.. if you change the topology your blocking port will go 
fwding but only after learning and listening unless you have portfast/uplinkfast 
etc

Steve