I have a 2811 router with a subrate T3/E3 installed in it. When I run a "sh hardware" it shows the card is present, yet a "sh int" does not appear to show it, not can I appear to configure it in any way. The IOS installed should support T3 cards from the research that I did. Is there something special I need to do to be able to configure the card?
You do not mention what the card is so it is hard to be sure what the issue is. But many of the T3/E3 cards require using the command
to define whether this is for T1 or E1 use. After this is configured then the interface is created and you can configure it. So give it a try with card type t3 and let us know what happens.