Finding all DNS aliases for a host using nslookup/dig/host or similar command

[Dave Olker]

Hi Patrick,

I think Jeff's point is that when you use DNS as your resolver, it appears to only return the alias names if you search using an alias name. In your first two examples you were using /etc/hosts for resolution. In the 3rd example you used DNS but you specified the alias name. Try #3 again using the real name. On my system I get:

# nslookup www.yahoo.com
Name Server: rose-resolver.americas.hp.net
Address: 15.251.192.51

Trying DNS
Non-authoritative answer:
Name: www.yahoo.akadns.net [Admin: The link is no longer valid> Broken Link removed]
Addresses: 66.94.230.44, 66.94.230.46, 66.94.230.43, 66.94.230.32
66.94.230.51, 66.94.230.37, 66.94.230.48, 66.94.230.42
Aliases:


# nslookup www.yahoo.akadns.net  [Admin: The link is no longer valid> Broken Link removed]
Name Server: rose-resolver.americas.hp.net
Address: 15.251.192.51

Trying DNS
Non-authoritative answer:
Name: <>www.yahoo.akadns.net [Admin: The link is no longer valid> Broken Link removed]
Addresses: 66.94.230.48, 66.94.230.46, 66.94.230.33, 66.94.230.44
66.94.230.52, 66.94.230.42, 66.94.230.32, 66.94.230.50


The first query returns the alias name because I searched using the alias name. The 2nd query did not return the alias name because I specified the "real" name.


Rich - is this the same behavior you get? If you search using an alias name do you get all the aliases but when you search using the "primary" name you don't get the aliases, or are you not getting alias information at all?

Regards,

Dave

[Patrick Wallek]

I just tried the same thing on one of my HP-UX 11.0 boxes and the aliases do NOT show up. I wonder if it is patch related......

[Jeff_Traigle]

I just got home and did some experimenting... this issue seems to be platform specific and HP doesn't handle it like MS, Apple, or Red Hat. Here's what I tried...

I have a DNS server set up for my home network. I have two CNAME records set up for the Linux system. With no corresponding PTR records for the CNAME records, the only way I could get any of the lookup tools (nslookup, nsquery, host) to return the aliases was to use the alias as the argument in the lookup command query as I stated previously... and then it would only return that particular alias, not all of them.

When I added PTR records for each CNAME, the differences in implementation surfaced. On MacOS X, Windows XP, and Red Hat Fedora Core 2, doing the lookup on the IP address would return all aliases regardless of the tool used. On HP-UX, it doesn't. (I'm patched upto June 2003 for required patches and Sept. 2003 on Support and Hardware Enabled patches on 11.11.)

I would personally classify this as a bug in HP's implementation since everyone else at least returns the aliases with an IP address provided if the PTR records are in DNS.

[Jeff_Traigle]

Oops. I take that back... nslookup on WinXP only returns the A record and not the CNAME records when given the IP address when the PTR records are present... but, then again, we all expect MS stuff to be broken, right? :)

I looked for "nslookup" in the patch database and found PHNE_30068 for 11.11. (There were several others all related to OV.) Applying it didn't solve the problem, but it did change the behavior of the results (or I just noticed the behavior after the patch anyway)... doing the nslookup or nsquery cycles through the A record and CNAME records in its results when the IP address is supplied (not in a regular fashion that I can determine), but still doesn't show them all.

[R Cardwell]

Thanks for all the responses, I have had a look at the responses and tried the various solutions that have been presented however, I still can't get the output I'am after.

The host aliases are definately in DNS, as I can perform nslookup's on each hostname and and they all return the same IP address. The only difference is when I do a nslookup on the primary hostname it just returns the IP, whereas when do perform an nslookup lookup on an aliases, it returns the primary hostname, ip address and an additional alias field with the alias name. Reverse lookups of the IP address always return the primary hostname without any reference to the aliases.

Rich Cardwell.

nb: I applied the latest DNS/BIND patch, and this hasn't fixed the output.

[Muthukumar_5]

Hai,

If you have aliases for that host / ip-address then you will get the informations of all aliases.

It is good to have your work / tries to analyse more.

Try to check as,

nsquery hosts "dns"

nsquery hosts "dns"

nsquery hosts "dns"

Are you getting differences over there.

Pls specify the informations and tests you have done and difference to forums so that all will give their views.

[Geoff Wild · Accepted solution]

This is how to get the CNAME:

dig @DNSSERVER yourdomain.com axfr |grep CNAME |grep HOST

Example:

dig @mydnsserver mydomain.com axfr |grep CNAME |grep server1
w052.mydomian.com. 14400 IN CNAME server1.mydomain.com.

Rgds...Geoff

[R Cardwell]

Bingo, Geoff's answer gets the result I was after, seems a little inefficient to pull all the hostnames from my domain, but it it works oh well.

Thanks for your help everyone.

Rich Cardwell.