ISC dhcpd failover question

Simon Hobson dhcp1 at
Fri Mar 13 07:42:47 UTC 2009

Matt Causey wrote:

>We have a fleet of remote sites.  Each site looks like this in terms of dhcpd:
>server A(primary) and server B(secondary)
>Say server B drops off the face of the planet.  Server A continues
>handing out addresses in 'communications-interrupted' mode.  But
>eventually it exhausts it's leases - and starts spewing "peer holds
>all free leases".
>So, is there anything in there that causes the primary to give up on
>the secondary eventually - and start pillaging its leases?  Or do I
>need to handle that condition with some external logic?

You need to put Server A into "Partner Down" state, then it can use 
all the addresses defined.

This isn't automatic since there isn't actually a way to be certain 
that the partner isn't able to talk to clients - there are several 
network topologies and fault conditions that could result in A and B 
not being able to communicate with each other, while still being able 
to communicate separately with clients. So it was left to the network 
admin to do the diagnosis and decide on the best course of action.

Some people have automated this with scripts.

Simon Hobson

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author Gladys Hobson. Novels - poetry - short stories - ideal as
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