Information Technology Reference
In-Depth Information
Figure 2-6
dCEF Components
RP
ARP
RIB
FIB Process
Adjacency
FIB
IPC
LC
LC
FIB
FIB
FIB Process
FIB Process
Adjacency
Adjacency
There are four types of consistency checkers:
•
lc-detect
—The line card sends any addresses of packets to the RP for which it could
not forward packets. If the RP detects that it has the relevant entries, an inconsistency
has been detected, and an error message is printed. The RP sends a signal back to the
line card confirming the inconsistent prefixes.
•
scan-lc
—Line cards scan their FIB tables on a periodic basis (60 seconds by default,
but this can be configured) and send the next
n
prefixes to the RP.
n
currently is 100
but can be configured. The RP does an exact lookup. If it finds any prefixes missing,
it reports an inconsistency. Signaling to the line card happens as just described.
•
scan-rp
—This is the opposite of scan-lc, with the RP doing the scanning. This time
the line card signals any verified inconsistencies to the RP.
•
scan-rib
—RP scans the IP RIB periodically to ensure that entries are also present in
the RP FIB table. This checker also works in nondistributed CEF.
In all cases, the error messages are reported on the RP only. The consistency-check
infrastructure always keeps statistics on the detection mechanisms, as well as recording
detailed information for a number of confirmed inconsistencies (currently four). The result
of the inconsistency check can be displayed with
show ip cef inconsistency
. You can use
the following methods to clear the inconsistency:
•
If a prefix is missing from a line card, use
clear cef linecard
slot
.
•
If a prefix is missing from the RP, use
clear ip route *
.
•
To reset the consistency checkers, use
clear ip cef inconsistency
.
