Replace gateway device

[yulianto piyut]

All,

My network team have a plan to replace catalyst device consists of default gateway used by servers.
What i must to do to make my server still connect to gateway? the ip for gateway is still same.

[Laurent Menase · Accepted solution]

if the dead gateway detection is on, this should work ok, but if they cut the old one after enabling the new one, there will be a race for arp, - if their mac differ, and the connection may take time to identify it, but the dgd will refresh the internal route entries when the first will be cut
( 3min max usually)

if dgd is off, then if the old one is cut after the new one is connect, there will be an unsolicited arp emited by the new one, then the old one will defend its arp and resent a new arp, making a new ire. That new ire will leave for about 20mn at most, so my be a good idea at that time to reduce ip_ire_flush_interval to reduce that time during the switch.

[yulianto piyut]

Default configuration for hp-ux 11.31 for dead gateway detection is 1 (on). Currently, my server using APA (LAN Monitor, active standby) for network multipath. This ip (configured with APA) connected to 2 catalyst. One of this catalyst is problem and network team plan to replace it. Catalyst that will be replaced has been set as default gateway.

to minimal downtime, what must I do?
disable default gateway detection?

can server detect automatically for the new catalyst (with new mac address)? how long it?

[Laurent Menase]

don't disable dgd default is good

if the 2 catalysts can be used as gateway,
and if the 2 are default gateway, it should work ok just replace.

again if the 2 can be default gateway, and the 2 are configured as gateways, just remove the default gateway to the one to replace, change it, then reenable it.

in fact many possibilities.

[yulianto piyut]

thanks,

only 1 catalyst is configured as default gateway.

[Laurent Menase]

just avoid that the 2 catalysts ( the old and the new one) have duplicate ip, so disable the old one interface before enabling the new one,
should work
you can also use an intermediate ip address configured on the new one,
then configure a route default to that ip, remove the old default gateway route, shutdown the one to be replaced, enable the old gateway address on the new one, reput the routes.


or you can just stop your old one, replace.
- tcp connections can wait up to 10min before resetting by default.