P2P T1 on 1720

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Sep 19th, 2007
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Good Afternoon,

I have two 1720 routers with WIC1DSUT1 WIC cards that we are using for a P2P T1 connection. I have attached the config from one of the routers. The config is the same on the router except for the IP and the clock source internal command on the other router. Currently the serial interface will come up for about 30 seconds and then the line protocol will drop. I believe that I set the clocking on the routers correctly, but I may be wrong. Is there anything else that I need to setup to get this T1 to work correctly?

Thank you for your help.

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Overall Rating: 5 (1 ratings)
sgelli Wed, 09/19/2007 - 14:45
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Is this a real T1 line or is it a back to back connection between the routers?

Try configuring "no keepalive" under the main serial interface and if this is a real T1 line, the Telco could be providing the clock (clock source would be line on both routers in that case). If it is a back to back connection, clocking is fine.


cyber-burn Wed, 09/19/2007 - 19:55
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This is an actual T1 line. The no keepalives and changing the clock source to the line on both ends did work to bring the line up. I am getting EIGRP updates across the line, but I am unable to ping the interfaces on either side of the line. Is there anything else that I'm missing that could be causing the problem? With the day I've had its probably something simple that I've overlooked

Thanks for the help

Edison Ortiz Wed, 09/19/2007 - 20:07
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How are you getting EIGRP updates when you stated at the beginning on the thread that serial goes down. Hmm...

Can we see the output from

show frame pvc


show int s0

Is this a new circuit or was it working before ?

cyber-burn Wed, 09/19/2007 - 20:29
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Hello Edison,

In the last post I stated that adding the no keepalives statements and changing the router at our main facility to service-module t1 clock source line instead of service-module t1 clock source internal brought the line protocol up, but I am still unable to ping the IP of the interface on the other side of the T1. However I do see that EIGRP learned the partner relationship once the serial interface came up. When I get back to the office tomorrow I can pull the frame pvc and serial information for you.

Thank you for your help

Sorry, forgot to mention that this is a new circuit that I am working on. I was able to get everything else up and working for this site, except for this particular circuit.

sgelli Thu, 09/20/2007 - 08:31
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I guess the only problem you are seeing is that you are not able to ping the directly connected interface on the Frame-Relay link. Try changing the Frame-Relay encapsulation to IETF on the main serial interface - "encapsulation frame-relay ietf" on both the routers.

Edison Ortiz Thu, 09/20/2007 - 12:54
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The show frame pvc output should be able to tell us if the telco did their job on provisioning the circuit for you.

cyber-burn Thu, 09/20/2007 - 15:51
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I appreciate the help. Sorry that I didn't respond before now but its been another hell of a day. Been running around like a chicken with my head cut off trying to deal with server problems etc.

The show output that you requested is in the attachment. Thank you for your help!

Edison Ortiz Thu, 09/20/2007 - 16:04
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It seems the telco provisioned the line as point-to-point but you decided to use frame-relay encapsulation instead of going the simple route with encapsulation ppp.

Any reasons for that ?

Can I see the 'show frame map' and 'show ip route' from both routers ?

cyber-burn Fri, 09/21/2007 - 09:40
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Thank you for your help Edison. My mistake was assuming that the line was ordered how I was told to set it up. I reconfigured the router for PPP and its up like a charm now. I apprecite your help and that catch. I've had a really long week...

Thank you all for your help!


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