L2L VPN Drops Every 5 Mins with Linksys Router and AT&T U-Verse 2 Wire RG

Hi everyone - hoping someone may have experienced this or have some insight for me:

I have a linksys VPN router (WRG54G) that does a Lan-to-Lan VPN tunnel to my office (VPN Concentrator).  I had Time Warner cable Internet for years and all worked fine.  I switched to AT&T U-Verse on Thursday and here is what I have done:

AT&T has a 2Wire residential gateway.  I changed the private address of the 2wire so it doesn't conflict with my Linksys.  On the 2Wire, I put the Linksys router into the DMZPlus Mode and the Linksys then got the public IP address on its interface.  So far, so good and I was able to change my VPN Concentrator at work and the VPN tunnel came up and two-way communications are fine.

However, I now noticed the L2L VPN tunnel drops literally every 5 minutes, all day long.  It reconnects itself after about 15-20 seconds.  This is evident by looking at my Cisco MARS logs and I can see the public IP drop exactly at 4 minutes, 59 seconds all day long.

Obviously not good.  Anybody have a fix for this or experienced something similar?  

Thanks much!
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Rob WilliamsCommented:
A couple of thoughts:
-In the two wire unit there may be a keep alive setting which you can enable, if not there may be an idle time out. If so set it to 0 which disables it.
-As a test try pinging the remote site with the continuous -t option for more than 5 minutes and see if it maintains the connection.
rvthostAuthor Commented:
Hi RobWill -

Thanks for the comments.  Unfortunately, I have yet to find a keep alive setting so I'm not sure it exists on the 2Wire.  I did try the ping and I drop two packets every 5 minutes when the VPN dies.
Rob WilliamsCommented:
That is very odd that it would drop when there is definite activity. I don't know what other options you might look at. MTU is a very common cause of dropped connection but it would definitely not be as consistent as you have reported.
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rvthostAuthor Commented:
Very odd indeed, I banged my head against it all weekend.  I did notice the MTU was set at 1500, perhaps I can put 1492 and see if it helps at all.  Like you said, it shouldn't be that consistent though where it drops every 5 mins.  

Also, I have an ASA 5505 that I may put in place of the Linksys VPN router, see if it helps at all, but I kinda doubt it.
Rob WilliamsCommented:
You mentioned you have a WRG54G that creates a VPN tunnel? That is not a VPN router is it?
The RV042's have an option in the advanced VPN configuration for "keep alive" though I am doubtful that will help if the ping didn't work.

If tinkering with the MTU, I would try a radical change as a test, like 1260. If you see a change then tweak.
rvthostAuthor Commented:
Sorry, that was a typo in my original post.  It's a WRV54G.  

- I just turned on the keep alive option, see if it does anything.  
- I'll play with the MTU tonight and report back.

Thanks for the ideas so far!
Rob WilliamsCommented:
AH yes WRV54G works. Let us know how you make out. Sorry we haven't been able to provide anything more beneficial so far.
rvthostAuthor Commented:
No problem at all, appreciate the guidance.

I played with the MTU, but no luck, VPN still drops every 5 mins.  I'll swap out the Linksys with the ASA next week and post back with my results.
Rob WilliamsCommented:
I will be very curious to hear if there is any difference. In the mean time perhaps others will have some suggestions.
rvthostAuthor Commented:
Hi Rob -

Well, good news!  I swapped out the Linksys with an ASA 5505 and the tunnel remains up all the time.  So apparently the Linksys just stopped playing nice once it was behind the AT&T 2Wire gateway instead of being directly connected to a cable modem.  

Thanks for the assistance!  If acceptable, I'll just accept your last comment as solution to throw a few points your way.

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Rob WilliamsCommented:
Glad to hear you were able to get it working rvthost. Odd that that would resolve the problem, but the ASA 5505 is definitely a much more stable unit.

Accepting the last post is fine, or you can request a refund as you resolved the problem on your own. I'm happy either way :-)
Cheers !
Rob WilliamsCommented:
Thanks rvthost.
Cheers !
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