Two Identical Setups, One Works, the Other Stopped!

[phipac]

I feel like I should be able to figure this out but...

I have two identical setups running HE tunnels.  Both are running through DD-WRT routers.  Before you panick, start laughing, start chiding, etc., know that I have had these working for years!  :)  Indeed, one of the setups still works like a charm, with uninterrupted IPv6 access.  However, recently, my other tunnel stopped working properly.  Here are the specifics on the tunnel that is not working:

1. It is set up IDENTICAL to the tunnel that works.
2. From a computer behind the router, I can ping the IPv6 address of the router.
3. From a computer behind the router, I can ping both the Client IPv6 Address and the Server IPv6 Address of the tunnel.
4. I cannot ping any other IPv6 address.  I get "Destination unreachable: No route".

With these being identical setups, routers, firmwares, and operating systems (CentOS Linux) on the computers doing the pinging, what are the possible causes for the failure of one to find a route?  If you need/want any additional information, I will be happy to oblige.  Thank you very much for helping!

[broquea]

So from a client PC running CentOS, you can ping6 the remote HE side of the tunnel? the x:x:x:x::1, and not get any farther? Is this running 2.6.18 with the broken default route that need 2000::/3 specified instead of ::/0?

[phipac]

No, 2.6.32.  And anyway it is the same result from my android devices and Windows XP and 7 boxes behind the router as well.

An additional interesting piece of information.  From the ROUTER, I can ping any IPv6 address.  If I ping an IPv6 address from the ROUTER, then immediately go to one of the computers and ping that address, it works.... for about 10 seconds.  Then I loose the route again.

This is really strange!

[broquea]

I'd paste your configs that you have in place. If you are using RADVD, did you make certain to add an IP from that routed range to the LAN facing interface? If you set it up in init scripts, have you verified that the IP is in fact on the interface? Are you using the routed space for the LAN? Don't obfuscate your configs if pasting.

[jtcloe]

Since you can ping both sides of the tunnel from a pc on the inside of your router (i.e. directly connected networks), that shows the router is establishing the tunnel.

Since you can't ping beyond any directly connected networks, that shows the router, although connected, doesn't have a default (ipv6) route.

[kasperd]

4. I cannot ping any other IPv6 address.  I get "Destination unreachable: No route".

Which address do you get the error from? And please do give us some actual information about your configuration. You are not going to get much help if you expect us to guess what the problem is.