Re: [LUG] Two DrayTek Vigor modems on the same LAN

You really want to have one draytek as the gateway and dhcp server. All the machines point to that, and it'll route to the second modem. Having multiple routes for client machines is doable, but trickier.Â

Machines -> Router 1 -> Internet OR Router 2.

The draytek should allow you to specify a secondary WAN under Wan -> Internet Access (if it's like our 28x0 series ones)

Wan1 would remain your existing adsl.Â

Wan2 would be set to Ethernet -> Static/IP.Â

Both are on the same subnet. Router 1 does dhcp and can failover to the whichever link is active in the event of one dropping. ÂBoth can be on the LAN segment, no need to put Router 2 directly onto the WAN2 plug of Router 1. That will allow you to contact it in case of Router 1 total failure. (Newer Drayteks IMO have proved less than reliable)

Gateway for all clients will be assigned by dhcp from Router 1 to be router1 itself, which will then, well, route.Â

Our 28?0's are smart enough to load balance by this and some basic settings. It works well, and I do it at home too with a secondary talktalk adsl so my very rural home ends up with 2x 2mbit connections which equates to a fairly usable system.

You can set static routes too, which are sometimes useful for ip-restricted access that you have, or vpns.

If you have two dhcp servers on any network, it's a recipe for randomness, especially if they're set to allow any new client. You should never give the same ip ranges to two dhcp servers though. 9 times out of ten, any unexplained weirdness on a network will be IP conflict. Having two dhcp servers which are ignorant of each other assinging from the same pool is going to cause issues. Â(This is why there are master/slave setups, but you probably don't need that here. Just have one and turn off everything else. Use linux's dhcp and turn off the drayteks' dhcp if you need more control than they can give you)

On 13 September 2014 22:29, Martijn Grooten <martijn@xxxxxxxxxxxxxxxxxx> wrote:

At work, we have a LAN, which is connected to the Internet using a
DrayTek Vigor 120 ADSL2+ Ethernet Modem(*), which I once got after
someone (Gordon, I believe) recommended it. It's been giving me a lot of
pleasure. (Of course, that pleasure is mostly the absense of pain the
previous BT router had been giving us.)

One of the boxes on the LAN is set up as the gateway and, through a
second interface, is connected to the modem. The box does all the DSL
stuff. All works well.

At the same time, another machine also had a direct connection to the
Internet, connecting to a BT router through a second interface. That's
useful for maintenance purposes.

But we have now replaced that router with another DrayTek modem of the
same make. And things don't really work.(**) There may be hundreds of
reasons for this, but I wanted to check if my reasoning is correct.

(1) Having two modems connected to machines on the same LAN - although
on second interfaces on each machine - shouldn't be an issue, should it?

(2) The modem creates its own mini-LAN for maintenance. So it assigns
the machine IP address 192.168.2.10 through DHCP and assigns itself IPO
address 192.168.2.1. This allows you to connect to its web interface. Is
it a problem if both modems use the same IP addresses?

I don't think either should be a problem - assuming one doesn't do funny
things with the routing - but I have a tendency to make daft mistakes
when designing a network.

Thanks

Martijn

(*) http://www.broadbandbuyer.co.uk/products/7898-draytek-v120/

(**) The current issue is that we can't reach the modem, even though it
has assigned an IP address to the machine connecting to it.

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