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Building a Linux IPv6 DNS Server

Issue 114

From Issue #114
October 2003

Apr 12, 2006  By David Gordon and Ibrahim Haddad
 in
A tutorial on building a DNS server node that provides IPv6 name resolution, with examples of some useful IPv6 applications.

One output file is produced: /var/named/master/secv6.your.domain.signed. This file should be referenced by /etc/named.conf as the input file for the zone.

The remaining configuration files are localhost.zone (Listing 3), localhost.rev (Listing 4), secv6.rev (Listing 5) and secv6.int (Listing 6). The difference between reverse lookup zone files secv6.rev and secv6.int is that one can be specified using A6 strings (that do not need to be reversed in secv6.rev) and the other with reverse AAAA format addresses in secv6.int. For instance, ping6 can refer only to secv6.int domain because it does not support A6 format.

Listing 3. /var/named/master/localhost.zone 


// localhost.zone  Allows for local communications
// using the loopback interface
$TTL 86400
$ORIGIN localhost.
@ 1D IN SOA @ root (
42 ; serial (d. adams)
3H ; refresh
15M ; retry
1W ; expire
1D ) ; minimum
1D IN NS @
1D IN A 127.0.0.1

Listing 4. /var/named/master/localhost.rev 

// localhost.rev  Defines reverse DNS lookup on
// loopback interface
$TTL 86400
$ORIGIN 0.0.127.in-addr.arpa.
@ IN SOA 0.0.127.in-addr.arpa. hostmaster.secv6.your.domain. (
42 ; Serial number (d. adams)
3H ; Refresh
15M ; Retry
1W ; Expire
1D ) ; Minimum
NS ns.secv6.your.domain.
MX 10 noah.ip6.your.domain.
PTR localhost.

Listing 5. /var/named/master/secv6.rev 

// secv6.rev  Defines reverse lookup for secv6
// domain in A6 format
$TTL 86400
$ORIGIN secv6.arpa.
@ IN SOA secv6.arpa. hostmaster.secv6.your.domain. (
2002011442 ; Serial number (yyyymmdd-num)
3H ; Refresh
15M ; Retry
1W ; Expire
1D ) ; Minimum
NS ns.secv6.your.domain.
MX 10 noah.your.domain.
; fec0:0:0:1::/64
$ORIGIN \[xfec0000000000001/64].secv6.arpa.
\[x0250b7fffe1435d0/64] 1D IN PTR pc2.secv6.your.domain.
\[x0250b9fffe000131/64] 1D IN PTR pc3.secv6.your.domain.
\[x0250b7fffe143617/64] 1D IN PTR pc6.secv6.your.domain.
\[x0250b7fffe1435c4/64] 1D IN PTR pc4.secv6.your.domain.
\[x0250b7fffe14361b/64] 1D IN PTR pc5.secv6.your.domain.
\[x0250b7fffe14365a/64] 1D IN PTR pc7.secv6.your.domain.
\[x0250b9fffe00012e/64] 1D IN PTR pc1.secv6.your.domain.

Listing 6. /var/named/master/secv6.int 

// secv6.int  Defines reverse lookup for secv6
// domain in AAA format
$TTL 86400
$ORIGIN secv6.int.
@ IN SOA secv6.int. hostmaster.secv6.your.domain. (
2002011442 ; Serial number (yyyymmdd-num)
3H ; Refresh
15M ; Retry
1W ; Expire
1D ) ; Minimum
NS ns.secv6.your.domain.
MX 10 noah.your.domain.
; fec0:0:0:1::/64
$ORIGIN 1.0.0.0.0.0.0.0.0.0.0.0.0.c.e.f.secv6.int.
0.d.5.3.4.1.e.f.f.f.7.b.0.5.2.0 IN PTR pc2.secv6.your.domain.
e.2.1.0.0.0.e.f.f.f.9.b.0.5.2.0 IN PTR pc1.secv6.your.domain.
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 IN PTR pc1.secv6.your.domain.
1.3.1.0.0.0.e.f.f.f.9.b.0.5.2.0 IN PTR pc3.secv6.your.domain.
7.1.6.3.4.1.e.f.f.f.7.b.0.5.2.0 IN PTR pc6.secv6.your.domain.
4.c.5.3.4.1.e.f.f.f.7.b.0.5.2.0 IN PTR pc4.secv6.your.domain.
b.1.6.3.4.1.e.f.f.f.7.b.0.5.2.0 IN PTR pc5.secv6.your.domain.
Starting DNS Dæmon

Once the installation and configuration steps are complete, you are ready to start the DNS dæmon on pc2. Named uses /etc/named.conf by default, although you can specify a different configuration file with the -c option if you want. Depending on where you installed the dæmon, enter: 

pc2% /usr/local/sbin/named

One additional configuration step is needed on the machines within the IPv6 network: update /etc/resolv.conf (Listing 7) to contain the DNS server's IP address. It is important that the IP address is included and not the hostname of the DNS server, because this file is where the system looks to find the address of the DNS. In other words, if you specified the hostname of the DNS server here, how would the system know what IP address corresponds to the DNS' hostname?

Listing 7. /etc/resolv.conf on Client Machines 

# To enable secv6 domain, start named on pc2
# and use this file as /etc/resolv.conf
search secv6.your.domain
nameserver fec0::1:250:b7ff:fe14:35d0
Testing the Setup

We use two simple methods of testing the setup. The first verifies that A6 addresses are enabled in the DNS server, and the second verifies that AAAA addresses are supported by the DNS server. The tests were performed on pc2. We present only the meaningful output here; otherwise the listing would be too long. For the first example, we use the DNS lookup utility dig to perform a lookup on secv6 domain in A6 format (Listing 8). We then perform a lookup in AAAA format (Listing 9). In both cases, we are not specifying an address to look up, thus our use of 0.0.0.0.

Listing 8. A6 DNS Query 


pc2% dig 0.0.0.0 secv6.your.domain a6
; <<>> DiG 9.1.0 <<>> 0.0.0.0 secv6.your.domain A6
[...]
;secv6.your.domain. IN A6
;; ANSWER SECTION:
secv6.your.domain. 86400 IN A6 0 fec0::1:250:b7ff:fe14:35d0
;; AUTHORITY SECTION:
secv6.your.domain. 86400 IN NS ns.secv6.your.domain.
;; ADDITIONAL SECTION:
ns.secv6.your.domain. 86400 IN A6 0 fec0::1:250:b7ff:fe14:35d0
ns.secv6.your.domain. 86400 IN AAAA fec0::1:250:b7ff:fe14:35d0

Listing 9. AAAA DNS Query 


pc2% dig 0.0.0.0 secv6.your.domain aaaa
; <<>> DiG 9.1.0 <<>> 0.0.0.0 secv6.your.domain AAAA
[...]
;secv6.your.domain. IN AAAA
;; ANSWER SECTION:
secv6.your.domain. 86400 IN AAAA fec0::1:250:b7ff:fe14:35d0
;; AUTHORITY SECTION:
secv6.your.domain. 86400 IN NS ns.secv6.your.domain.
;; ADDITIONAL SECTION:
ns.secv6.your.domain. 86400 IN A6 0 fec0::1:250:b7ff:fe14:35d0
ns.secv6.your.domain. 86400 IN AAAA fec0::1:250:b7ff:fe14:35d0

For our second test, we include samples of an SSH session connection, first using an IPv6 address and then using an IPv6 hostname.

______________________

Comments

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good overview

Anonymous's picture
Submitted by Anonymous on Thu, 02/25/2010 - 11:53.

I think this has helped me understanding how to set
up my ipv6 (only) network. The sytax's are good examples
thanks

Problems with IPv6 DNS files

KenS's picture
Submitted by KenS (not verified) on Thu, 06/01/2006 - 04:11.

This article is interesting. Unfortunately, when I tried to apply the article, I encountered multiple typos in the listing files, which wasted a lot of time. For instance, Listing 1 is missing the closing }; for the options. Listings 3-6 use double-slash comments, which are errors in zone files. The zones "secv6.int" and "secv6.arpa" don't make sense. The lines that start with "IN" are missing significant whitespace. Eventually I gave up on these listings.

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