What Is a Protocol-Dependent Module (PDM) in EIGRP?
EIGRP can route more than one network-layer protocol at once, and the mechanism that makes this possible is the Protocol-Dependent Module (PDM). Each PDM handles everything specific to one particular routed protocol — building its own neighbor table, its own topology table, and interfacing with the shared DUAL algorithm — while DUAL itself remains protocol-agnostic....
