REQUEST: Network Interface Failover and multi-DNS resolution

[Doncho N. Gunchev]

On 2004-08-12 (Thursday) 22:04, Carlos Rodrigues wrote:
> I have a box with two ethernet cards, each one connected to a different 
> local network ("staff" and "students"). Each one of the networks has a 
> DNS server to resolve internal names.
> 
> The problem is: I can only resolve hosts that are on the eth0 connected 
> LAN ("staff"). To access hosts on the other network I have to use their 
> IP address directly.
> 
> This prompts me to request two features (independent of each other):
> 
>    1. be able to resolve names using both DNSes;

    Just put them both in /etc/resolv.conf, or better - fix them to
know of each other's zones. You can also run local DNS server, which
you can tell where to look for what, but this is not a workstation's
function - fix/link your DNS servers/network. At least, you can use
/etc/hosts as it was in the beginning...

>    2. that there be some failover for network connections.
> 
> By failover I mean being able to define one interface as "primary". The 
> primary interface would set the default gateway and all that 
> global-unique stuff (including resolv.conf, without feature 1.).
> When that interface goes down, those global settings are changed to the 
> ones provided by another active interface. If the primary interface goes 
> up again, it restores the initial configuration.

    Why not just use DHCP?

> 
> This would be very useful for cases such as a laptop with wired and 
> wireless networking. The "wired" connection would be the primary 
> interface. The "wireless" connection would take over if the "wired" one 
> goes down (they may be different networks, e.g. we have a totally open 
> and untrusted wireless lan and our linux users can't just unplug the 
> cable and move around, they are forced to restart the interfaces).

    You can add 2/more default gateways. In this case linux uses 'Dead
Gateway Detection' - see http://www.ssi.bg/~ja/dgd-usage.txt for example.
I've never used two network interfaces with DHCP, so I've never tried
this trick with DHCP, but you can :)
...

-- 
Regards,
  Doncho N. Gunchev    Registered Linux User #291323 at counter.li.org
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