Fail over serves on different VLANS

[Klaus Vink Slott]

Hi

We have been running 2 dhcp servers in fail over configuration for quite 
a while. Now we consider moving one server to a host in another 
building. This will also place the host on another VLAN.

In a earlier tread here John Wobus <jw354 at cornell.edu> wrote:
 > As far as I know, DHCP redundancy works by having the servers
 > offer different addresses and the client picking one. ISC
 > DHCP servers reduce the obvious duplicated effort by having
 > one of the two DHCP servers wait a few seconds to see if the
 > other server makes an offer. But if the one server doesn't
 > pick up on it's peer's offer, the address it offers itself
 > is always a different one.

How does the server "see if the other server makes an offer". Do they 
need to bee on the same VLAN or is it communicated directly between the 
servers?

-- 
Regards
Klaus Vink Slott