Configuring and Managing MPE/iX Internet Services (MPE/iX 6.0)

134 Chapter 8
DNS BIND/iX
Data Files
Each entry will indicate the IP address in reverse order, then the host
name. For example, for host littledog.maxx.net, whose IP address is
204.251.17.249, in the zone.ADDR file it’s PTR entry would look
like:
249.17.251.204. IN PTR littledog.maxx.net.
Why is it backwards? Recall that DNS does its parsing from right to
left, from most inclusive to most specific. For IP addresses, it needs to
parse in the same direction. But IP addresses, from right to left, go from
most specific to most inclusive. So the simple answer is to reverse the
IP address in the NDS PTR records. Now DNS can parse in the same
direction, and resolve in the same order — from most inclusive to most
specific.
A shortcut in PTR records is often used. It looks like this:
249 IN PTR littledog.maxx.net.
If the dot is left off the IP address in the PTR record, DNS will complete
the IP address with the IP address of the domain, specified in the file’s
SOA record. This is also true for A records in name-to-address mapping
db files. If the dot is left off, DNS will automatically try to complete the
name with the full domain name in this zone. Paying attention to the
terminating dot is important.
For the zone.LOCAL file we describe the loopback address just as you
would expect it, now that we know we have to reverse it. The PTR entry
in the zone.LOCAL file would look like:
1.0.0.127. IN PTR localhost.
or, using the shortcut:
1 IN PTR localhost.
Only one line from named.conf remains to be discussed, the “cache”
entry. This is a bit of a misnomer as it doesn’t have anything to do with
local caching. Instead, it defines the master root domain name servers
for the Internet. You can retrieve this list from
ftp://nic.ddn.mil/netinfo/root-servers.txt. You will need to
check this site periodically to ensure you have the latest list.
This file lists the root domain servers in human-readable format. You’ll
need to reformat it for consumption by named. Here’s what the cache
file looks like:
; Servers from the root domain
; ftp://nic.ddn.mil/netinfo/root-servers.txt
;
. 99999999 IN NS A.ROOT-SERVERS.NET
. 99999999 IN NS B.ROOT-SERVERS.NET
. 99999999 IN NS C.ROOT-SERVERS.NET
. 99999999 IN NS D.ROOT-SERVERS.NET
. 99999999 IN NS E.ROOT-SERVERS.NET
. 99999999 IN NS F.ROOT-SERVERS.NET
. 99999999 IN NS G.ROOT-SERVERS.NET
. 99999999 IN NS H.ROOT-SERVERS.NET
. 99999999 IN NS I.ROOT-SERVERS.NET