I have just had a cable line (not in the UK) installed as a backup to my VDSL line and am trying to connect it to my 2850 on WAN2.

The cable line and modem seems to be fine. If I connect a laptop directly to it then I can surf. The phone on the line also works fine.

I have tried various setting and I can get WAN2 to go green (connected) using the following settings:

General Settings: WAN2 > Enabled; Auto negotiation; Always on

Internet Access: WAN2 > Static or Dynamic IP; Enable; Always on; Obtain an IP automatically; DNS server IP Addresses set to OpenDNS

The problem is that as soon as WAN2 goes green (in addition to WAN1) I can no longer communicate over the web.

Where have I gone wrong?

what are you mean can not communicate over the web? The led is green meaning is up but has not connection to internet?
I would say delete the open dns servers and leave the page blank
also go to load balance and tick only wan 2 if will give you access

You can also try at WAN >> Internet Access >>> specify MAC address (to clone it) ... for some cable modems this is important

Also make sure dhcp or nat or icmp are turn off at cable modem so will not cost issues with both router turned on

Here in UK usually cable connection need static or dynamic ip but if is not in the UK other options are to try pppoe or L2pt/ppptp

babis3g wrote: also go to load balance and tick only wan 2 if will give you access

That was the solution. I did not realize that the default load-balance policy settings, where nothing is enabled, meant that nothing passes out.

I enabled the 1st line and selected WAN1 without any other changes and WAN1 now works.

WAN2 is still not working. If I select WAN2 only on the load-balance policy settings then there is no internet, so I will work through your other points.

Thank you

at load balance if nothing is ticked it means it should work both connections same time

when clicked any wan, the 2850 is forcing to use only the selected wan

if you clicked the wan 2 (cable) and you have unticked the wan 1 and still is not working that means is something wrong with the cable connection ... i would say check and change the DNS servers or leave them blank (to use the default ones from isp) and the other suggestions

Reboot cable modem as well ... sometimes it helps

babis3g wrote: at load balance if nothing is ticked it means it should work both connections same time

when clicked any wan, the 2850 is forcing to use only the selected wan

Just tried that and indeed it worked. So it must be that a badly configured connection can stop the good one as well.

I do now have it working after getting assistance from the ISP support.

The required setting is LT2P and after a couple of failures we got it to work. Thanks for your assistance.

Does it make any difference whether I have both load balance lines ticket or neither?

Ok nice is up and running ... i did mentioned to try (but as last option) pppoe or PPtP etc

For load balance yes it does matter

If you have wan 1 first in the list (top) that wan will always work first (even if is ticked both wans)
If you set wan 2 then this will work all times so it will be as primary connection

If any connection fails lets say wan 2 top of list and second ticked the wan 1 ... then wan 2 will always work and if wan 2 fails with in 5-10 seconds should be ready up and running the wan 1 (at wan internet general set up both at always on)

If you need rules like priority or choice of line for games or emails etc .... it is possible but i never set them ... sorry

I am just happy have wan 1 ticked at top because is unlimited internet (but is adsl so is slower connection) and when i need upload youtube etc a heavy or faster use i just untick the wan 1 (wan 2 is always ticked remember) and within seconds is changing connection

To understand what i mean practice little
Go at System Status is by default when logging in and keep the ip addresses ... now go to http://whatismyipaddress.com/ and keep untick/tick the wan's to see how works and how fast (refresh each untick/tick the what is my ip address.com)

Enjoy your new machine I love it

PS when none is ticked then the 2850 will load balance both lines same time (but usually wan 1 it will be use more frequent because i think is the design of it)