Migration of leases from one failover pair to another without outage

[Holger Honert]

> Step 1:
>
>  +---------+                           +---------+
>  | +-----+ |                           | +-----+ |
>  | |testa| | <-----------------------> | |testa| |
>  | +-----+ |                           | +-----+ |
>  +---------+                           +---------+
>  primary-a.test                        secondary-a.test
>
>                                        +---------+
>                                        |         |
>                                        |         |
>                                        |         |
>                                        +---------+
>                                        secondary-b.test
> To here:
> Step 2:
>
>  +---------+                           +---------+
>  | +-----+ |                           |         |
>  | |testa| | <---------\               |         |
>  | +-----+ |            \              |         |
>  +---------+             \             +---------+
>  primary-a.test           \            secondary-a.test
>                            \
>                             \          +---------+
>                              \         | +-----+ |
>                               \------> | |testa| |
>                                        | +-----+ |
>                                        +---------+
>                                        secondary-b.test
>
> Stage 1:
> In /etc/dhcpd.conf on primary-a.test:
>
> failover peer "testa" {
>         primary;
>         address primary-a.test;
>         port 520;
>         peer address secondary-a.test;
>         peer port 520;
>         max-response-delay 60;
>         max-unacked-updates 10;
>         mclt 3600;
>         split 128;
>         load balance max seconds 3;
> }
>
> In /etc/dhcpd.conf on secondary-a.test:
>
> failover peer "testa" {
>         primary;
>         address dhca1.test;
>         port 520;
>         peer address secondary-a.test;
>         peer port 520;
>         max-response-delay 60;
>         max-unacked-updates 10;
>         load balance max seconds 3;
> }
>
"peer address" should be primary-a.test!

> Stage 2:
> failover peer "testa" {
>         primary;
>         address dhca1.test;
>         port 520;
>         peer address secondary-b.test; # CHANGED => need restart.
>         peer port 520;
>         max-response-delay 60;
>         max-unacked-updates 10;
>         mclt 3600;
>         split 128;
>         load balance max seconds 3;
> }
>
> In /etc/dhcpd.conf on secondary-b.test:
>
> failover peer "testa" {
>         primary;
>         address dhca1.test;
>         port 520;
>         peer address secondary-b.test;
>         peer port 520;
>         max-response-delay 60;
>         max-unacked-updates 10;
>         load balance max seconds 3;
> }
>
> Or indeed, I'd love to hear any other suggestions for migrating leases
> from one failover pair to another without an outage.

My suggestion:

stop the secondary-a, transfer the leasefile to secondary-b, stop (or 
restart) primary-a and startup secondary-b at the same time.

keep in mind to tell dhcp-relays, i.e. routers or layer3-switches to use 
the new secondary-b server.

HTH

Regards

Holger



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