Cisco Cisco IOS Software Release 12.0(13a) Fehlerbehebungsanleitung
interface alone, the no ip route−cache cef command is added. This disables CEF switching for that interface
alone. Cisco IOS does not add the no ip route−cache command to the running−config on its own when it is
forced to disable CEF. It was introduced on many platforms in Cisco IOS 12.0 mainline, particularly low−
and mid−range platforms such as the Cisco 1600, 2500, and 3600 Series.
alone. Cisco IOS does not add the no ip route−cache command to the running−config on its own when it is
forced to disable CEF. It was introduced on many platforms in Cisco IOS 12.0 mainline, particularly low−
and mid−range platforms such as the Cisco 1600, 2500, and 3600 Series.
When a router receives a packet on a routed interface, it first removes the Layer 2 (L2) frame information. It
then stores the Layer 3 (L3) packet in Input/Output (I/O) memory. What happens next depends on the
switching path that the packet follows.
then stores the Layer 3 (L3) packet in Input/Output (I/O) memory. What happens next depends on the
switching path that the packet follows.
Verification Steps
These steps can be used to confirm that packets follow the CEF switching path:
Confirm that CEF is enabled globally and on a particular interface.
router#show ip cef
%CEF not running
Use the ip cef command in global configuration mode to enable (central) CEF.
Note: On the Cisco 7200 Series, CEF is the default Cisco IOS switching method in an
upcoming release of Cisco IOS.
upcoming release of Cisco IOS.
a.
Use the show ip cef prefix command and confirm that prefixes are listed.
router#show ip cef
Prefix Next Hop Interface
0.0.0.0/32 receive
192.168.0.0/30 attached Serial2/0/0:1
192.168.0.0/32 receive
b.
1.
Confirm that CEF is enabled on a particular interface.
Use the show cef interface x/x command to look for "IP CEF switching enabled," or "IP
distributed CEF (dCEF) switching enabled."
distributed CEF (dCEF) switching enabled."
router#show cef interface fastEthernet 0/0/0
FastEthernet0/0/0 is up (if_number 2)
Internet address is 192.168.1.253/24
ICMP redirects are always sent
Per packet loadbalancing is disabled
Inbound access list is not set
Hardware idb is FastEthernet0/0/0
Fast switching type 1, interface type 18
IP Distributed CEF switching enabled
Fast flags 0x0. ifindex 1(1)
Slot 0 Slot unit 0 VC −1
Hardware transmit queue ptr 0x48001A00 (0x48001A00)
Transmit limit accumulator 0x48001A02 (0x48001A02)
IP MTU 1500
a.
Use the show ip interface command to display the enabled Cisco IOS switching methods.
router#show ip interface fastethernet 1/0/0.1
FastEthernet1/0/0.1 is up, line protocol is up
IP fast switching is enabled
IP fast switching on the same interface is enabled
IP Flow switching is disabled
IP CEF switching is enabled
b.
2.