Home » Cisco » 300-101 » What is indicated by the for an address?
Refer to exhibit. What is indicated by the for an address?
A. CEF is unable to get routing information for this route.
B. CEF cannot switch packet for this route and passes it to the next best switching method.
C. A valid entry and is pointed to hardware based forwarding.
D. CEF cannot switch packet for this route and drops it.
Correct Answer: B
Explanation/Reference:
Glean adjacency in short when the router is directly connected to hosts the FIB table on the router will maintain a prefix for the subnet rather than for the individual host prefix. This subnet prefix points to a GLEAN adjacency. Punt adjacency When packets to a destination prefix can’t be CEF Switched, or the feature is not supported in the CEF Switching path, the router will then use the next slower switching mechanism configured on the router
Correct Answer: B
Understand CEF Punts
The term “punt” is defined by Cisco to describe the action by an interface’s device driver of sending a packet “down” to the next fastest switching level. This list defines the order of preferred Cisco IOS switching methods (from fastest to slowest).
– Distributed CEF
– CEF
– Fast switching
– Process switching
A punt occurs under these conditions:
– The next lower level did not produce a valid path or, in the case of CEF, a valid adjacency. In other words, if the CEF lookup process failed to find a valid entry in the forwarding information base, the packet is punted to the next available switching path or dropped.
– A particular feature or Layer 2 encapsulation is not supported at the lowest level. If CEF supports a particular feature, ownership of a packet is passed through a set of software routines in the CEF “feature path.”
– A feature requires special handling.
A punt adjacency in CEF is installed when some output feature is not supported in CEF. CEF punts all packets that go to such an adjacency to the next best switching mode, in order to switch all the packets.
center#show ip cef 45.0.0.0
45.0.0.0/8, version 184, 0 packets, 0 bytes
via 1.1.1.1, Tunnel0, 0 dependencies
next hop 1.1.1.1, Tunnel0
valid punt adjacency
CEF Packets passed on to next switching layer
Slot No_adj No_encap Unsupported Redirect Receive Bad_ttl Options
RP 0 0 0 0 5700 0 0
2 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0
5 0 0 0 0 0 0 0
8 0 0 0 0 0 0 0
9 0 0 0 0 0 0 0
10 0 0 0 0 0 0 0
https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-software-releases-120-mainline/47205-cef-whichpath.html