What is a possible cause for the incomplete marking?

Refer to the exhibit.

A network administrator checks this adjacency table on a router.

What is a possible cause for the incomplete marking?
A . incomplete ARP information
B . incorrect ACL
C . dynamic routing protocol failure
D . serial link congestion

View Answer

Answer: A

Explanation:

To display information about the Cisco Express Forwarding adjacency table or the hardware Layer 3­switching adjacency table, use the show adjacency command. Reasons for Incomplete Adjacencies There are two known reasons for an incomplete adjacency: The router cannot use ARP successfully for the next-hop interface. After a clear ip arp or a clear adjacency command, the router marks the adjacency as incomplete. Then it fails to clear the entry. In an MPLS environment, IP CEF should be enameled for Label Switching. Interface level command iproute-cache cef No ARP Entry

When CEF cannot locate a valid adjacency for a destination prefix, it punts the packets to the CPU for ARP resolution and, in turn, for completion of the adjacency.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/17812-cef­incomp.html#t4