[ale] Routing and failovers

Derek Atkins warlord at MIT.EDU
Thu Jul 9 09:59:43 EDT 2015


Hi,

Alex Carver <agcarver+ale at acarver.net> writes:

> Anyone have experience setting up dual WANs for failover (my guess is
> there's a couple of you or I wouldn't really email the list ;) ).
>
> I'm thinking about putting in a cellular modem at home to act as a
> secondary/backup WAN link for critical functions (alert emails, security
> system access) in case the primary WAN (DSL) drops.  I don't want
> traffic going over that link unless the DSL is dead so this is a true
> failover rather than a load balance (or I suppose it's a load balance
> with a ratio of infinity weighted towards the DSL)
>
> My first thought was to use something like a Ubiquiti EdgeRouter Lite
> (maybe need to go to the EdgeRouter 8, not sure) with two WANs
> configured and then the NAT and public assignments behind the third
> port.  It appears EdgeOS can do two WANs but it's not clear from what
> I've been able to dig up so I wanted to find out if there are
> other/better options or suggestions.

If you've got a routable network you could set up tunnels on both sides
and use something like BGP to choose which link to use.

However if you're just using NAT and trying to decide "hey, my main link
is down, let me switch over to using NAT over the other link", then I'm
afraid I don't know a good way to do that.  You probably don't want to
have this automated, because all your existing connections will break if
that happens.

-derek
-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available


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