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Obsolete Releases => SME Server 7.x => Topic started by: kadybee on April 27, 2012, 04:08:52 AM

Title: DNS respond to eth0 alias
Post by: kadybee on April 27, 2012, 04:08:52 AM

Hi

I am moving a corporate DNS server and attempting to get an established SME 7.5.1 to respond to DNS requests on an IP aliased on eth0.

SME Server:  192.168.1.254 as Server only - will respond to the 192.168.1.0 network for DNS lookups with no issue;

I have aliased the IP 192.168.1.20 to eth0:0 - (this was a another box handling DNS requests for local network users);

The alias IP responds to ICMP etc yet won't provide NSLookup responses.

As the .20 IP - and .254 IP - are hardcoded in a number of machines, I was looking at a quick way of removing the current DNS machine, using the SME server and then tidying up the network with DHCP to avoid the hardcoding of previous operators!

I am assuming it may be an iptables thing, yet not being familiar with that and knowing I can't use aliases for iptables, I am hoping there may be a suggestion or workaround for this (bind / tinydns config etc). 

I could put a second NIC in the machine if necessary, but currently think that will just exhibit the same problem??  Being a production mail server I am trying to avoid downtime.

Any thoughts / assistance greatly appreciated.

Title: Re: DNS respond to eth0 alias
Post by: kadybee on April 30, 2012, 02:53:43 AM

Workaround resolved:

To get around the DNS not responding to the aliased IP address, I simply changed the strategy to swap the Prime/Alias addresses over!

ie as per above: 

Change Server IP to .20  - Alias original Server IP of .254

Strangely, all services that I need (POP/IMAP/SMTP/SSH) respond on the alias IP address just not DNS.

This seemed the simplest workaround without getting into the config of the DNS responder.  It wasn't an iptables/masq issue as that was turned off.