Hi all, thanks for taking the time to read this post. Hopefully it will be a no brainer for someone.
I have the Vigor 2860n set up with a Wireless ISP as the primary connection into WAN 2 via a wireless bridge and a very slow ADSL connection as the failover connection on WAN 1.
I have configured the router to detect via ping to the WISP's gateway whether the primary connection fails and have tested this and it works perfectly.
However something came up earlier that could be a problem.
The WISP gateway (which is on a dedicated BT fibre line) lost connection to the internet due to a service outage on BT's side.
So while the router is still able to ping the gateway, it doesn't actually have a working internet connection. Only it doesn't know this because it's still able to ping the gateway.
I need to ping past the gateway to ensure I still have internet connectivity in the event this happens again.

Can anyone suggest an IP that I can set the router to ping that

a) responds to the ping request,
b) is stable enough that it will keep responding to the ping and
c) won't stop responding to the ping thinking it's an ICMP flood attempt?

Do Draytek themselves have a server that I can use for this?

I tested the Vigor using ARP as the disconnection detection method and it didn't seem to work, that would obviously be the easiest solution but I had no luck with it.
Also, what TTL setting should I use for the ping? I am using 255 at the moment and that seems ample. Pinging between the Wireless bridge and the gateway takes anything from 7 - 20ms so 255 is fine right?
I also have to say that I've configured a LOT of routers in my time and I am very impressed with the feature set, value for money and usability of the Draytek range.

Many thanks in advance.

SeanTheMac wrote:
Can anyone suggest an IP that I can set the router to ping that

a) responds to the ping request,
b) is stable enough that it will keep responding to the ping and
c) won't stop responding to the ping thinking it's an ICMP flood attempt?

Google DNS? 8.8.8.8 / 8.8.4.4

Yep, that's what I use. 8.8.8.8

God forbid Google DNS servers ever go down, as we use them everywhere

Thanks guys, I use google as my DNS servers as well. Didn't think of using them to ping. :oops:

How about the TTL query? Is 255 too high?

I'm not sure TTL comes into it, as it is only pinging 8.8.8.8 which has never changed, so caching shouldn't be an issue.