In an Ethernet switched network, a PC in one location is unable to communicate with another PC in a remote location, which are configured in the same IP subnet. **Which of the following is most likely to be the first step to take when troubleshooting the issue?**

In an Ethernet switched network, a PC in one location is unable to communicate with another PC in a remote location, which are configured in the same IP subnet.
Which of the following is most likely to be the first step to take when troubleshooting the issue?

Make sure that Dynamic Trunking Protocol is enabled.

Make sure that both of their switchports are configured in the same VLAN.

Make sure that the VLAN is carried across the trunk links.

Make sure that the Native VLAN is set with the default value.

Make sure that the VLAN is allowed on the trunks.

Explanation

All the mentioned steps are proper for troubleshooting a VLAN issue, however if the switchport is not configured with the correct VLAN, it will never work. The first and most important step when troubleshooting VLANs is to check the VLAN port memberships with the command: show vlan id [vlan-id]. - - - - -{enhanced explanation 20151221} - - - - - - - - - - - Real-World-Reality-Check= 1st question: Have these hosts EVER successfully communicated before? IF YES, they have communicated before, most likely is a link-down, somewhere between them, SECOND-QUESTION: Are other similar hosts similarly affected? - - - - - - - IF NEVER, (communicated before) most likely a misconfiguration, - - - - - - - - - - Real-World-Reality-Check#2 = telent to both end-point switches =[1] "show-ip-interface-brief" (on newer IOS's use the new super-cool: "show-interface-status) - (look for: bad NIC, bad-cable, bad-port, port-security-violation) - - [2] make sure you can ping end-switch to end-switch to eliminate connectivity as an issue - - -[3] "show-vlans brief" to check vlan assignments [4] Start investigating trunk interconnections to make sure that all necessary vlans are being: trunked/allowed - [Good-Luck!]