56K Frame Relay Problem

[mob]

I have three lines coming into a 1720 router. I have had problems with the newest line since day one. It appears that the line goes up and down during business hours (no problems after hours). The line provider has run tests over and over and said the problem is in my hardware. I have replaced the router and wic and the problem persists. Now I am having the same problem on a line that has been running for over a year. The router shows that the line is down, if I wait 5-10 minutes the line comes back up or if the router if powered off and on it comes back up. Any help as to what I can check or where to look for additional help would be great.

[robhorniachek]

This sounds like a problem at the demarc... When the provider runs the test, are they testing directly to your router, or just to the SIJ? You might want to have them come out and test from your location - it could be a bad termination, bad cable, etc. Make sure that when they do that, they use all of the cables you are using.

The fact that it only happens during business hours may indicate that the termination point is in a high-traffic area, and when people walk by they might be (inadvertantly) knocking or wiggling the wire. Now you are having problems on a proven good circuit, so the wiggling has deteriorated that termination as well...

[rjackson]

Are the interfaces showing any errors? The router will reset the interface when keepalives fail. that can be caused by high error rates. Check both ends with sho int. If there are errors clear them with clear count and watch how fast they go up. Also look at resets in sho int before you clear counts. that shows when router has reset int due to errors or loss of carrier.

[michael-faust]

You say that the router says that the line is down, but you don't tell me what is down. RTS? DTR? CTS? DSR? CS? Line protocol? Lets take these one at a time.

DSR Data Set Ready. Brought high by the DCE when it has completed it's POST and is ready to go. If DSR goes low no data can be sent. "show Int" will show the current state. If it goes low, look for a CSU/DSU or cabling problem. It could also be your WIC, but you already tried changing that.

CS Carrier Sense Brought high when the DCE is sensing carrier from the DCE at the other end. "show int" will tell you the state of CS. If it goes low no data can be sent. Remember, this is a full duplex line so the other end could be happy. If CS goes low, does the CSU send 'yellow alarm'? It should. Does the other end get the yellow alarm? This will be the service providor's CSU (CSU, frame relay switch, DACs, etc.). If DSR is up and CS is down, check the line.

CTS Clear to Send. Brought high by the CSU/DSU when DSR and CS are high. "show int" will show the state of CTS. Sometimes is configured to follow RTS or CS or to be high at all times. It is only valuable as a troubleshooting aid if the configuration is known. Check the configuration of the CSU. You might try locking it high.

DTR Data Terminal Ready. Brought high by the router when "no shut" command is given and DSR, CTS and CS are high. "show int" will show the state of DTR. If it ever goes low when CTS, DSR and CS are high, you probably have a bad WIC or it is shut down.

RTS Request to Send Brought high by the router when it is ready to send. "show int" will show the state of RTS. When the interface is configured and ready, RTS should be high. If not, check the configuration and the WIC.

Line Protocol Brought high by the router when the interface is up and the router is able to talk to the frame relay switch. Watch the LMI exchange. It is the LMI exchange that controls line protocol. "show int" will show the number of requests and replys. They don't have to match, but they should increment in step every 10 seconds by default. If they don't increment try debugging the LMI exchange. Also, be sure that you know what the providor has set for their LMI timer. You should set your timer at least 2-3 seconds less than theirs. This will keep the timers from expiring.

Look at these things the next time it goes down and get back to us if you need more direction.