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Defined in RFC 1035. Forward maps a host name to IPv4 address. The only parameter is an IP address in dotted decimal format. The IP address in not terminated with a '.' (dot). Valid host name format (a.k.a 'label' in DNS jargon). If host name is BLANK (or space) then the last valid name (or label) is substituted.
name ttl class rr ip joe IN A 192.168.254.3
If multiple addresses are defined with the same name then BIND will respond to queries with all all the addresses defined but the order may change. Cyclic order is the BIND default but you can control it with the BIND named.conf statement rrset-order. The same IP may be defined with different names (Beware: in this case a reverse lookup may not give the result you want). IP addresses do not have to be in the same class or range.
Note: A RRs translate a name to an IPv4 address - the name does not have to be the real host name of the PC or server (as it appears in /etc/hosts). It can be or not as you choose. Thus if your servers's name is joe.example.com with an IP address of 192.168.2 1 and it provides, say, a DNS service then you can either define an NS RR for joe.example.com or define an NS RR for, say, ns1.example.com and an A RR for ns1.example.com A 192.168.2.1.
; zone fragment for example.com $TTL 2d ; zone default = 2 days or 172800 seconds joe IN A 192.168.0.3 ; joe & www = same ip www IN A 192.168.0.3 ; functionally the same as the record above www.example.com. A 192.168.0.3 fred 3600 IN A 192.168.0.4 ; ttl overrides $TTL default ftp IN A 192.168.0.24 ; round robin with next IN A 192.168.0.7 mail IN A 192.168.0.15 ; mail = round robin mail IN A 192.168.0.32 mail IN A 192.168.0.3 squat IN A 10.0.14.13 ; address in another range & class
In the above example BIND will respond to queries for mail.example.com as follows (assuming you are using the default rrset-order order cyclic):
1st query 192.168.0.15, 192.168.0.32, 192.168.0.3
2nd query 192.168.0.3, 192.168.0.15, 192.168.0.32
3rd query 192.168.0.32, 192.168.0.3, 192.168.0.15
4th query 192.168.0.15, 192.168.0.32, 192.168.0.3
3 reverse map
4 dns types
5 install bind
8 dns records
12 bind api's
13 dns security
bits & bytes
notes & tips
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