Local Network Traffic Fails Until External Connection
Posted on 2005-04-20
This is one of the strangest things I've seen.
I have two machines running Windows Server 2003 at our colocation facility connected through a brand new Netgear switch. (I just changed the switch because I suspected it was responsible for the behavior I am about to describe.) One machine is our web server, the other is our database server. They are both accessible through RDP. They are both located behind a firewall which is doing NAT.
I started investigating this problem when the code I was running on the web server was having intermittant connection problems connecting to the database server.
Here is the scenario: I log on using RDP to both machines. I open a command prompt and setup a perpetual ping to the other machine using their local addresses. ping -t 10.2.2.2 on one machine and ping -t 10.2.2.3 on the other machine.
Everything looks fine. The pings reply with zero packet loss. I log off of both machines, leaving the ping command running. I continue testing my app. After a while, my app on the web server is unable to connect to the database. I log back on to the database machine, and see that the command prompt shows that the pings are failing. However, as soon as I have logged back on, the pings start succeeding again, and everything works again.
So it looks like connecting to the machine from the outside world somehow solves the local network problem. I have no clue why this would be, but those are the results as I see them.
Do you have any idea what is going on? Obviously this is an unacceptable situation and needs to be resolved, but I don't know how to proceed.
I have replaced the switch. Now I am considering replacing the network card, but I don't have any evidence that the card is the culprit.
Thanks for your help.