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Communicating
with a DHCP Server
If your network uses DHCP to assign IP
addresses to computers, you might not be able to enter a fixed IP address in
your zone file because the IP address might be determined when the DHCP client
boots, and could change between boots of the client.
Configuring Other Computers via DHCP, discusses two solutions to this problem:
Configuring the DHCP server to assign a consistent address to clients or
configuring the DHCP and DNS servers to communicate with one another. In the
first case, you must take care to configure the DHCP and DNS servers
consistently. For instance, if you want birch.threeroomco.com to be 192.168.1.2, you must set up that mapping in both the DHCP server's configuration files and in the DNS server's zone files (ideally, in both
the forward and reverse lookup zone files). This is a simple solution, but it
can be tedious for a large domain.
consult
addition to this section if you want to implement the inter-server
communication solution. The BIND side of the equation is implemented in the named.conf file's zone section that corresponds to the zone in question. Specifically, you
must add an allow-update option. For instance, such a zone definition might resemble the
following: zone "threeroomco.com" { type master; file "named.threeroomco.com"; allow-update { 192.168.1.1; } };
This configuration tells BIND to accept
update information sent from 192.168.1.1, which should be the DHCP server for
your network. You must make a similar change to the reverse DNS zone, if your
server handles that and if you've configured the DHCP server to perform both
forward and reverse updates.WARNING
align=left border=0> If your DNS server is exposed to the
Internet, or if your local users aren't 100 percent trustworthy, accepting
DNS updates even from a single remote computer can be risky. A miscreant
might manage to hijack the DHCP computer's address or masquerade as that
system, then make changes to your DNS server that might compromise other
systems that rely upon the veracity of the DNS server's data. You can
minimize your risks by running DNS and DHCP on the same computer, and
allowing updates only from the localhost (127.0.0.1) address.
