2 ADSL Lines on small office network.

    we are installing a second ADSL line to an office, for two reasons,

1) If one line falls over, maybe due to lightning strike - whatever - some sort of temporary physical layer problem - Then we would like to not loose internet connectivity _ Our local telecomms service tell us that we have two seperate wires back to the exchange, therefore knocking out one will not effect the over.

2) Would like to achieve - simple load balancing - IE. some PCs use one ADSL router - others use the second.

What I propose is as follows -

a) Each adsl router is set up with a different range of DHCP addresses so that they do not assign addresses in the same range.
b) Each connecting PC is set up with primary and secondary DNS entries - The primary address for each PC will point to the router designated to that PC. The secondary address will point to the fallback router (adsl line) for that PC, therefore if we swap over the primary and secondary addresses for half of the  PCs we should achive rudimentary load balancing and fall back capability.

Will it work ?

Thanks, ChrisColeman.    
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delmcConnect With a Mentor Commented:
Sorry I didn't see your earlier post, the points you made in that post are all valid.
Not quite as in the event of a failure you will need to reconfigure half the PCs to point at the other router.

You could go with the idea of having split DHCP where one router offers the - 126 range and the other offers .127 to .254  (or whatever scheme you choose). Then when the PCs boot they will be given an IP address by whichever router responds first. Trouble is you could end up with all the PCs on the same router with the other not being used.

Best bet would be to get gold of a load balancing router with 2 WAN ports.
take a look at these 2 items, maybe worth checking out http://www.draytek.co.uk/products/vigor2910.html or http://www.draytek.co.uk/products/vigor2820.html
recently started using these and they seem solid enough at a reasonable price, the 2910 is possibly the better option if you are using 2 adsl modems, if not the the 2820 is good as it has a direct connection for ADSL and the secondary connection would utilise a modem/ cat 5 connection. They offer detailed documentation on the help section of the website on how to configure successfully.
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ChrisColemanAuthor Commented:
Delme, thanks for that and it looks interesting.

But there is a problem - since the dsl lines enter the building (it's not a small building) at different points we would need to run a phone cable (or cat5 - but only to a DSL modem .) back to the draytek --- which unfortunately may not possible - they've just had the building redecorated.

What we need is to be able to connect two devices to the LAN ?



The 2910 would be the answer then, it can sit just in front of the server/ network and you can patch points from ADSL kit to the firewall via structured cabling, I presume that the DSL modem's have cat5 connections on the back, if so it would be a case of setting the ADSL modems up to pass all traffic to the Vigor 2910 (also setting each of the WAN ports to handle the ISP information) , then using port forwarding on the vigor to pass the relevant information to the server's/ PC's. I've set one of these up in a similar way where the ADSL comes in at the other end of the building, ADSL routers in question were thompson brand.
ChrisColemanAuthor Commented:
         thanks for that .. I think I understand --

Can i just run this by you ?

a) We will use the 2910 as a load balancer, and a direct  interface to a WAN feed, which could be a modem or a routers -  cat5.
b) A second WAN feed (eg. another router or modem) will be connected to the LAN anywhere in the building (actually in another building). This would be configured in the 2910 as a WAN feed - by fixed IP address.
c) In each of the connected PCs we set the 2910 as the gateway and as the DCHP host.
d) We configure port restrictions in the 2910s firewall.

Way to go?

Thanks, Chris.

There are 2 options
a) We use to have a Draytek setup to achieve what you are looking for you would need a draytek 2820 (just the standard unless you need wireless)  http://www.draytek.co.uk/products/vigor2820.html as well as a draytek 120 http://www.draytek.co.uk/products/vigor120.html. You would have the 2820 serving all your clients with DHCP etc. The 2820 has 2 wans and so both sets of adsl usernames and passwords. The 2820 has 1 adsl port and an ethernet port. So for the second adsl the 2820 uses PPPoE to pass the details to the second router.
more details at - http://www.draytek.co.uk/support/kb_vigor100_setup.html
This setup also means you have one router that needs configuring for any rules, vpns and a better load balancing etc. Becuase it has an ethernet port as a second wan it also means it is future proofed if you ever want a SDSL or leased line etc.
This setup will do basic load blanacing based on local rules for where to point traffic.

b) For true load balancing I would recommend what we currently run, a draytek 3300. This has TRUE load balancing http://www.draytek.co.uk/products/vigor3300v.html Its other features may be over kill but this would be your best bet while running seperate draytek 120's (or similar) It also means you can have up to 4 wanl connections (sdsl, adsl leased line etc) or 3 and a dmz for mail scanning etc. The 3300v is certainly worth the extra cash.

Hope this helps.
Hi Chris: If possible, I would choose Cable Internet & ADSL not ADSL & ADSL.. due to the fact that this is 2 different technologies instead of two of the same technology.  But if you are stuck with ADSL only as an option.. Choose 2 different providers instead of the same company.

As for connecting it all together. a Load Balancing router is the way to go..
I recommend the Sonicwall NSA 240..This can support up to 4 WAN ports if you want to add additional connections in the future:

Here is a demo of the admin page of the device:
g2g makes a very valid point, the Draytek 3300v is an excellent unit for achieving load balancing/ failover and does support 4 WAN ports. We have used this unit on a client site and it is configured with 3 ADSL modems (2 support one provider, 1 with another provider) This therefore means that they can have failover capability if either of the ISP's fails, what has also been beneficial is that the 3300v supports multiple VPN's for which we currently have 15 VPN tunnels all connecting different sites via the different ADSL connections (5 per connection). The sonicwall unit is also a good unit but if it comes down to cost then the draytek is a far more reasonable price. If you are just looking to implement 2 ADSL connection then a cheaper alternative is the Draytek 2950, http://www.draytek.co.uk/products/vigor2950.html
I have worked with both units and both are equally as good at what they do, but if I had a choice on what to work with the 3300v would be the one I would go with because of the ability to use Vlan's and VOIP.
ChrisColemanAuthor Commented:
Points awarded to DellMc - Most concise answer based upon origional question and parameters.

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