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Old 11-01-2006, 08:53 AM   #1
shinepuppy
LQ Newbie
 
Registered: Sep 2002
Location: Lewisville, Texas
Distribution: Debian / [K]Ubuntu
Posts: 13

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UDP Response with a Multihomed NIC


Hello All,
For various reasons, I have a server with one NIC multihomed with 2 IP addresses assigned:
PHP Code:
eth0   192.168.0.97
eth0
:192.168.0.96 
I am running a DNS server which listens on both IPs. When I run a DNS query on the ip address linked to eth0 I get a correct response:

PHP Code:
server 192.168.0.97
Default Server:  [192.168.0.97]
Address:  192.168.0.97

linuxquestions.com
Server
:  [192.168.0.97]
Address:  192.168.0.97

Non
-authoritative answer:
Name:    linuxquestions.com
Address
:  66.116.125.121 

When I query the multihomed IP I get an error:

PHP Code:
server 192.168.0.96
Default Server:  [192.168.0.96]
Address:  192.168.0.96

linuxquestions.com
Server
:  [192.168.0.96]
Address:  192.168.0.96

DNS request timed out
.
    
timeout was 2 seconds.
DNS request timed out.
    
timeout was 2 seconds.
*** 
Request to [192.168.0.96timed-out 

From what I can tell, the linux server receives the DNS query on eth0:1 (192.168.0.96) but replies with the correct answer from eth0 (192.168.0.97). My windows machine making the request isn't expecting a response from the *.97 address so it drops it.

Can anyone tell me how I can force the response out through the IP address in which it was received? I believe this is a routing problem but I have not been able to figure it out.

Here is what my routing table looks like:
PHP Code:
root@0[powerdns]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    
Use Iface
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        0 eth0
0.0.0.0         192.168.0.1     0.0.0.0         UG    0      0        0 eth0 
thanks!
 
  


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