DNS Enumeration might give you information on other hosts in the network. Keep in mind, you will probably have to mess with /etc/conf for this!!!
If you are looking for DNS servers specifically, use nmap to quickly and easily search:
nmap -sU -p53 $network
Normal DNS Query:
nslookup $IP
Query for MX Servers within a domain:
dig $domain MX
Query for Name Servers within a domain:
dig $domain NS
DNS Zone Transfer (This will give you all of the marbles!)
dig axfr @$nameServer $domain
dnsrecon -d domain -a --name_server server
If you want to brute force subdomain enum, try dnsmap:
dnsmap $domain