Thanks! I did get a part number for a dual T1/E1/PRI card for the Network Module slot -

NM-2CE1T1-PRI - but am not sure if that will work in the 2821 with the multilink group configuration we intend to use on the six T1 lines. Would that work or are the VWIC cards a better choice here?

Yup, thats the one. It looks like it is supported in the 2821. It doesn't look like you gain anything from using this module over the VWIC, except maybe ISDN functionality.

The VWIC would take up less space in the chassis, so you'd still have your NM slots available for ESW (ethernet switch) modules. It may just come down to price, though.

Maybe more detail would help. We already have four WIC-1DSU-T1-V2 cards in each 2821. Ideally I would like something simple, like a NM-2W network module that would accept two of the same type T1 cards already in use. This network module shows as being supported in the 2600, 3600, 3700 and 3800 series routers but unfortunately not the 2821....darn! Since replacing all existing WIC cards with VWICs is likely way more expensive I am thinking that the 2 port E1/T1/Pri network module is the best choice. Hey, it does have an internal DSU, right?