Cisco Cisco IOS Software Release 12.0(2b) Guide De Dépannage
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.
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.
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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."
particular feature, ownership of a packet is passed through a set of software routines in the CEF
"feature path."
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A feature requires special handling.
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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.
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
With an incomplete adjacency, CEF considers that the router as a whole (including all the other switching
paths) does not know how to get to the adjacent node. We punt packets to process switching in order to kick
off some resolution protocol like Address Resolution Protocol (ARP), which results in the adjacency being
completed some time later. In this condition, CEF punts one packet every two seconds to the next switching
path to avoid a flood of packets. Thus in this condition, pings to the IP address might fail about 50 percent and
you see a "!.!.!.!.!" ping pattern. This condition also occurs when the CEF table is corrupted, as indicated by a
difference between the show ip route command information and the show ip cef command information for a
particular IP address.
paths) does not know how to get to the adjacent node. We punt packets to process switching in order to kick
off some resolution protocol like Address Resolution Protocol (ARP), which results in the adjacency being
completed some time later. In this condition, CEF punts one packet every two seconds to the next switching
path to avoid a flood of packets. Thus in this condition, pings to the IP address might fail about 50 percent and
you see a "!.!.!.!.!" ping pattern. This condition also occurs when the CEF table is corrupted, as indicated by a
difference between the show ip route command information and the show ip cef command information for a
particular IP address.
Note: On the Gigabit Switch Router (GSR), the line card (LC) generates Internet Control Message Protocol
(ICMP) echo replies from within CEF. If the packet is not destined to one of the GSRs local addresses, then
no processes is involved. It is switched straight through either in hardware or under interrupt in dCEF,
depending on which LC you use.
(ICMP) echo replies from within CEF. If the packet is not destined to one of the GSRs local addresses, then
no processes is involved. It is switched straight through either in hardware or under interrupt in dCEF,
depending on which LC you use.
On the GSR, fast switching and process switching are not available. If a destination prefix cannot be resolved
to a forwarding entry in the inbound LCs tables, the packet is dropped. Only packets that match a glean
adjacency are punted to the Gigabit Routing Processor (GRP). In addition, on the GSR, the LC CPU does not
punt packets to the GRP for features, and the LC sends an ICMP unreachable (as long as the no ip
unreachables command is not configured). On the GSR, the only traffic punted to the GRP are packets
destined to an interface on the router or packets sourced from the router.
to a forwarding entry in the inbound LCs tables, the packet is dropped. Only packets that match a glean
adjacency are punted to the Gigabit Routing Processor (GRP). In addition, on the GSR, the LC CPU does not
punt packets to the GRP for features, and the LC sends an ICMP unreachable (as long as the no ip
unreachables command is not configured). On the GSR, the only traffic punted to the GRP are packets
destined to an interface on the router or packets sourced from the router.
Related Information
IP Routing Support Page
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Technical Support − Cisco Systems
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