[Dnsmasq-discuss] Set outgoing IP-Address to dns-upstream-servers

[Michael Rack]

Well, in normal the routing have to be correct.

But my network is very complex. I have three upstream carriers with one 
static ip-address for each connection. Every interface is different in 
connection-type and connection-speed.

Over all interfaces i run a VPN-Tunnel 3x /30 Networks with public 
ip-addresses to interconnect with a Root-Server in Nürnberg (Germany).

A dynamic routing-protocoll set up my routes automaticly, even the 
default-route (0.0.0.0/0).

This setup allows me, to have a allways reliable innternet-connection.

My local-router in Salzburg (Austria) announces a /28 public ip network 
to serve all services behind the router.

Now to the Network-Setup:

            Nürnberg         Salburg
     tap1:  91.xx.15.49/30 < 91.xx.15.50/30
     tap2:  91.xx.15.53/30 - 91.xx.15.54/30
     tap3:  91.xx.15.57/30 > 91.xx.15.58/30

                             Announce: 91.xx.15.112/28
                             locally assigned: 91.xx.15.113

Legend:
   < and > indicates the way the packets will be sent (asynchron routing)
   - indicates a backup-link if one of tap1 or tap3 will fail

Now, i like that DNSMASQ use 91.xx.15.113 for querys to upstream 
dns-servers.

My dynamic routing-protocoll inserts this routing-entry into the 
default-routing-table:

	default via 91.xx.15.49 metric 1

no src-option is given by the dynamic routing-protocoll. The right way 
for all reasons is to define src 91.xx.15.113 if the packet does not 
contain an ip_src.

But my routing-protocoll doesn't support this.

Now DNSMASQ have to set the ip_src address, to supress linux-kernel to 
complete the outgoing packet.

Bye,
Michael.


Am 06.03.2009 16:20, schrieb Rance Hall:
>
> You do this with routes,  on a multihomed machine each IP address is
> also part of a network and is part of the route to get to that
> network.
>
> If you set up your routes correctly  (generally speaking the default
> is correct) then the correct local static ip is always used when
> leaving your box to go anywhere, including upstream dns servers.
 >