Which command is useful to see if network layer information is being received at a PSTN gateway?

'show gateway status' is not a valid standard Cisco IOS command for checking ISDN or PSTN network layer information.

'show isdn q931' displays active Q.931 call-by-call signaling messages and details, but does not summarize whether the network layer interface itself is up and receiving information.

'show ccm-manager status' checks the registration and connection state between a Cisco gateway and Cisco CallManager, which is unrelated to verifying PSTN network layer reception.

The 'show isdn status' command displays the status of all three ISDN layers - Physical (Layer 1), Data Link/Q.921 (Layer 2), and Network/Q.931 (Layer 3) - at each interface on the gateway. Because it summarizes whether the network layer is active and operational, it is the most direct way to confirm that network layer signaling is being received at a PSTN gateway.

'show isdn q921' reports Data Link layer (Layer 2/LAPD) statistics and state, not the network layer (Layer 3/Q.931) information needed to verify PSTN connectivity.