topic Re: IP Aliasing and DNS in Operating System - HP-UX

IP Aliasing and DNS

Ross Goldman_1 — Fri, 11 Oct 2002 18:27:46 GMT

Hi all. I have a 10.20 host that has IP aliasing on it. I'm trying to make the host a DNS primary and use the second (aliased, or "non real") address for this function. It doesn't work. When I try resolving using the aliased address I get "Specified server is not availiable." If I switch the IP addresses and now resolve using the "real" address it works fine. Could it be that the aliasing doesn't extend to the lower network protocol layers? Any help/suggestions would be appreiciated!

Re: IP Aliasing and DNS

steven Burgess_2 — Fri, 11 Oct 2002 19:12:16 GMT

Hi

If you don't get an answer, you could ask

http://www.acmebw.com/askmrdns/archive.php?category=83

HTH

Steve

Re: IP Aliasing and DNS

Tom Danzig — Fri, 11 Oct 2002 19:12:42 GMT

How did you make the alias? I would add a CNAME entry pointing to the real host name in the appropriate DNS zone file.

If you need to assign a different IP for this, you can use IP multplexing to assign another IP to an existing LAN card. An entry in the /etc/rc.config.d/netconf file for this would look like:

INTERFACE_NAME[5]=lan0:1
IP_ADDRESS[5]=10.1.1.123
SUBNET_MASK[5]=255.255.255.0
BROADCAST_ADDRESS[5]=10.1.1.255
INTERFACE_STATE[5]=up
DHCP_ENABLE[5]=0

lan0 would now have two IP's assigned to it.

Re: IP Aliasing and DNS

Ross Goldman — Fri, 11 Oct 2002 20:35:15 GMT

I'm doing the aliasing at the NIC level using ifalias. Sorry, should have specified that.

Re: IP Aliasing and DNS

Jordan Bean — Fri, 11 Oct 2002 20:38:28 GMT

Which version of BIND are you using? Have you reviewed the name server log for errors binding errors?

Re: IP Aliasing and DNS

Christopher Caldwell — Fri, 11 Oct 2002 22:08:30 GMT

netstat -an | grep .53\ | grep LIST

should show you something like
tcp 0 0 *.53 *.* LISTEN

Which says that named is listening for requests on all IPs for the given port.

If you're running 10.20 you're probably running a 4.x.x series named, which bound to ports using INADDR_ANY (listen on all IPs).

If you have a host with an ifaliased IP, make sure to point the db records for named to the IP (don't use CNAMES, make sure you have a revese name entry).

e.g.

Forward
A.B.COM IN A 1.2.3.4
NS1.B.COM IN A 1.2.3.5

Reverse
1.2.3.4 IN PTR A.B.COM.
1.2.3.5 IN PTR NS1.B.COM.

When you receive answers from this server, you'll get answers on the base IP, not the ifaliased IP, because of the way named binds to IPs in the 4.x.x series.