I am doing a PRI with Eschelon Telecom.

they have the switch type at DMS-500 and NI1 protocol.

is DMS 500 and DMS 100 the same. I don't see a selection for DMS 500

DMS100 and 500 are the same to the Legend/Magix. NI1 is a BRI protocol. You must use AT@T 4ESS or 5ESS Custom. Remember switch type and protocol are two completly different things. Most all recent releases of CO switchs can emulate any protocol.