Internet drops every 70 minutes

[iluska]

Hello,
Our company uses the Internet(DSL) for vital business functions. We brought in a Cisco router and a firewall and began to build a perimeter network. Previously the modem came into an SMC unmanaged router and there were no problems. Instability started to occur and now we drop the Internet every 70 minutes. A traceroute to the ISP default gateway restores the connection. I have worked with Cisco, our ISP, and an outside consultant to no avail. Has anyone seen anything like this before? We will be going to a T1 in a week but it would be nice to solve the problem before then. Thanks.
Joe

 

[JOAMON]

Is your current DSL static IP or dynamic IP?
If dynamic might be due to the ISP refreshing IP addresses.

 

[iluska]

Thank you . Joamin,

I have a static IP address. The period of 70 minutes is exact. A traceroute will re-establish the connection. We
are all baffled.

The line enteres near our PBX and there is a voice wiring closet very close to it. But RF interfence would xplain the regular period.

Joe

 

[NetworkGhost]

What kinf of FW do you have ? Where is the connection Dying?

FW ----> RTR ----DSL ? Is this how it is setup or
RTR ----> FW -----DSL ?

 

[KiscoKid]

To me this issue likely isn't something randomly occuring, i.e. line faults, equipment faults or anything of that nature. I base this on the fact that you say that exactly on 70 mins you lose connection.

Therefore this sounds to me more like an issue with something expiring or timing out, i.e. some kind of setting on the router or firewall.

I've seen issues with dynamic NAT doing something similar as NAT employs default timeout parameters for TCP and UDP streams (albeit 70 minutes is not a timeout default I recall).

To be fair, if you've paid for an expensive external consultant and involved Cisco TAC, I'm not hopeful it's something this simple.

I'd have probably rolled back to my previous installation using a DSL modem (as you say it worked fine) until the arrival of the T1.

Sorry I can't be of more help.

 

[JOAMON]

It does sound like a timer or keepalive issue. Could be that the ISP is clearing their ARP cache every 70 minutes or something of that nature. May not be anything with your equipment might be on their side.