I am not sure at this point why you have the problem when configuring the interface as Frame Relay and not a problem when configuring the interface as HDLC. Perhaps if you post the router configs we might notice something that would lead us to an answer.
Check to see that the 2801 has the DCE-end of the back-to-back cable, that the interface is set for DCE (show controller, ~top three lines, intf-type DCE), and that the clock-rate is set for the correct value.
Perhaps you have the cable reversed, and the 2600 is actually setting the clock rate (back to back cable have a DCE end and a DTE end).
We are pleased to announce availability of Beta software for 16.6.3.
16.6.3 will be the second rebuild on the 16.6 release train targeted
towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are
looking for early feedback from customers befor...
Introduction Featured Speakers Luis Espejel is the Telecommunications
Manager of IENova, an Oil & Gas company. Currently he works with Cisco
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worked as a Senior Engineer with the Routing P...
In this session you can learn more about Layer 3 multicast and the best
practices to identify possible threats and take security measures. It
provides an overview of basic multicast, the best security practices for
use of this technology, and recommendati...