It's an Edgelink 100. I put the loopback on the DS3 interface and then I get:
Global ISDN Switchtype = primary-ni
ISDN Serial7/0:1:23 interface
dsl 0, interface ISDN Switchtype = primary-ni
Layer 1 Status:
ACTIVE
Layer 2 Status:
TEI = 0, Ces = 1, SAPI = 0, State = TEI_ASSIGNED
Layer 3 Status:
0 Active Layer 3 Call(s)
Active dsl 0 CCBs = 0
The Free Channel Mask: 0x807FFFFF
Number of L2 Discards = 0, L2 Session ID = 42
Total Allocated ISDN CCBs = 0
Also, on the mux I put a loopback on the T1 side and the PBX that is connected comes up as well.
