When troubleshooting LDP operations on the Cisco IOS and IOS XE routers, what is one of the first things that should be verified?
A. if running OSPF as the IGP, ensure that OSPFv3 has been enabled
B. check if the ip cef command has been enabled
C. verify in the running configurations that all of the required LDP interfaces are defined under the mpls ldp command configuration mode
D. verify if there are any access lists that are denying TCP and UDP port 464 packets
