We have a customer with 2 sites, and a recently deployed 2Mb Leased line circuit between them. As the service provider does not provide routers, the customer has purchased an 1841 router for each site, along with a suitable serial interface to connect to the X21 interface on the provider eqpt.
With everything connected up, the serial interfaces come up ok (L1 and L2), and it's possible to ping/telnet to the remote router, and a server which sits on it's LAN interface. However, if we try to send a file to the remote server - the transfer starts to take place, and after about 10 seconds of transferring data the session times out, and we see CRC & input errors (equal in value) on the serial interface of the far end router.
I have cleared the counters to be sure, and can confirm that it's when the session dies, the counters increment.
I've tried a couple of things to try to get this working, one of which was to implement traffic shaping on the local router in the outbound direction to limit the rate at which the data was being sent. This made no difference, other than it took longer for the transfer to fail.
The Bandwidth on the serial interface at each end is configured ok. I've tried both HDLC and PPP encapsulation, and it makes no difference - the transfer still fails after a few seconds.
Both routers are running IOS 12.4-15.T7, and I've captured the config of the serial interface config for both routers, along with a 'show interface' on both routers
Any help or advice appreciated.