This read-write value controls how a port behaves while UDLD verification is still in progress: verifyThenForward(1) blocks the port until a successful UDLD exchange completes, while forwardThenVerify(2) lets traffic flow normally until the retry count is exceeded. Admins choose forwardThenVerify, the default, to avoid delaying link-up on ports where brief traffic loss during verification is undesirable, or verifyThenForward for stricter loop protection before any traffic is allowed. For example, a security-conscious admin might switch a sensitive uplink to verifyThenForward(1) so it never forwards frames until UDLD has confirmed bidirectional connectivity.