• Use to limit the scope of the debug commands
• Provides a centralized filtering system for voice and call processing debug and traces
• E.g. display only certain called or calling number

• Create Filter tag
• Configure incoming call filter
• Configure outgoing call filter

call filter match-list 16 voice
  incoming {called-number | calling-number | dialpeer | media | port | secondary-called-number | signaling}
  outgoing  {called-number | calling-number | dialpeer | media | port | secondary-called-number | signaling}

• To debug

Router# debug condition {application | called | calling | card | glbp | interface | ip | mac-address | match-list | standby | username | vcid | vlan | voice-port} [options] {exact-match | partial-match}

! *** E.g.
Router# debug condition match-list 16 exact-match

• Can also filter based on carrier-id or trunk group label

call filter match-list 16 voice
  source {carrier-id | trunk-group-label}
  target {carrier-id | trunk-group-label} 
! ** For example
  source carrier-id 228877
  target trunk-group-label 2546

• Identify the component that will use GCFM

Router# show call filter components

• Review the configured match-list

Router# show call filter match-list [list <number>]

• Verify the status of dynamic or match list-based GCFM conditions

Router# show debug condition [condition <identifier> | all]