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
Correct Answer: A
Explanation/Reference:
To display information about the Cisco Express Forwarding adjacency table or the hardware Layer 3-switching 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 enabeled for Label Switching. Interface level command ip route-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 t
urn, for completion of the adjacency.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/17812-cef- incomp.html#t4
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