CISCO Trunks, VTP mode and DTP verifications.

# Shows trunks on switch

# and allowed VLANS on those trunks

show interfaces trunk

# Use this command to verify VTP mode 
# running on switch. 3 modes;
# Server mode, Client and Transparent

show vtp status

# shows whether or not switch is 
# running dynamic trunk protocol (DTP)
# for example fast ethernet port 0/23

show interfaces fa0/23 switchport