Failing Backup link

[makemorebeer]

I'm not sure where to begin with this issue. it happened once while live and once while testing on the live system. in a network running a T1 (primary link), and two GRE Tunnels (backup links)and utilizing five routers we get the following. The T1 will fail (moron Cuts a trunk Fiber) and then it switches to the tunnels. did I mention we're using EIGRP for Routing. I'm pretty sure it's setup correctly because when the T1 goes down it fails over to the Tunnel connections. and everything continues normally with the exception of e-mail. for some reason e-mail at the remote site via outlook is interrupted even though you can ping and trace route the exchange server successfully. but then after about thirty to forty five minutes (happened both times) all higher level applications (SQL queries, printing, etc.) sending from remote to main site will stop working, event hough they've been working fine up to that point. what could possibly cause this. i don't know if it's a server issue, routing issue, line issue, bandwidth issue (i doubt this one based on the bandwidth graphs). I'm open to any ideas.

 

[Minue]

Hello
How are the router's setup. T1 and the tunnels are handle by 1 router per branch?
In any case I would start looking at tcp connection time-outs and the arp cache.
Regards

 

[makemorebeer]

Router setup is as follows

coreswitch-----Router1----T1----Router2---Coreswitch
| | |
| Router3-----ADSL----------------------Router5
Router4--------ADSL--------------------------|

So we've got the main site core switch connected to router1, router3, and router4. the remote site coreswitch is connected to router2, and router5. T1 is handled by routers 1 and 2
there are two GRE tunnels on router 5, and one GRE tunnel on both Router 3 and Router4
Routers 1 and 2 are cisco 1841 routers
Routers 3,4,and 5 are cisco 1811 routers

I'm sure it would help to post configs but at the moment i've got to reconfigure the routers. i didn't save the configs when i was working on them because i wanted to know if they were working first, and boom whole town lost power last night. if you'd like to see them though let me know and i'll post up.

Appreciate the help.

 

[Minue]

Hello
I don't think the config's are needed.Because this seems really to be an arp,netbios or tcp connection issue.It's the Router change that's causing the problem.I would advice testing with a R1 and R2 handing both connections (GRE and T1).
Regards

 

[makemorebeer]

so what you're saying is that it's getting confused running between so many routers? So then why do the lightweight apps like telnet, ping and traceroute still work but the heavy apps which access SQL don't. I mean that dosn't seem to make sense if it's losing it's route somewhere does it?

 

[Minue]

Hello
I don't think it's a routing issue.Because as you said "So then why do the lightweight apps like telnet.....".
SQL if I remember correctly is one of the picky protocols that gives problems with NAT and Firewalls.
Regards