Troubleshooting CEF

london#debug ip cef ?

accounting Accounting events drops events

Packets dropped by CEF IP CEF table events IP CEF fragmentation IP CEF hash events IP CEF IPC events Packets seen by IP CEF IP-prefixes related IPC Packets received by IP CEF IP CEF subblock events IP CEF table changes fragmentation hash ipc packet prefix-ipc receive subblock table london#debug cef ? all assert background

All CEF events CEF assert events CEF background events

Example 6-13 debug ip cef and debug cef (Continued)

broker CEF broker events consistency-check CEF consistency checker events elog CEF enable elog points epoch CEF epoch events fib CEF fib entry events filter Configure filter hardware CEF hardware api debugging high-availability CEF high availability events

interest

CEF interest list events

interface

CEF interface events

loadinfo

CEF loadinfo events

memory

CEF memory events

non-ip

CEF non ip entry events

path

CEF path events

switching

Switching infrastructure

table

CEF table events

xdr

CEF XDR events

Example 6-14 shows the interesting command show ip cef switching statistics, which tells where packets possibly have been dropped and why.

Example 6-14 show ip cef switching statistics

london#show ip cef switching statistics

Path

Reason

Drop

Punt

Punt2Host

RP RIB

Packet destined for us

0

86654

0

RP RIB

Total

0

86654

0

RP LES

Packet destined for us

0

39003

0

RP LES

TTL expired

0

0

101049

RP LES

Total

0

39003

101049

RP RSP

Packet destined for us

0

19491

0

RP RSP

No adjacency

0

0

1

RP RSP

IP redirects

0

0

4743

RP RSP

Total

0

19491

4744

Slot 0

Packet destined for us

0

19491

0

Slot 0

No adjacency

0

0

1

Slot 0

TTL expired

0

0

3

Slot 0

IP redirects

0

0

4743

Slot 0

Total

0

19491

4747

All

Total

0

164639

110540

Example 6-15 presents an overview of the most interesting show CEF commands in Cisco IOS. Notice that the router london has three routing tables and three CEF tables: the global routing table or Default routing table and the two VRF routing tables cust-one and cust-one-ipv4. A VRF routing table is a routing table used for one virtual private network (VPN) in a network that is running MPLS VPN. See Chapter 7 for a detailed explanation on MPLS VPN.

Example 6-15 show cef Commands

london#show cef table

Global information:

MTRIE information:

TAL: node pools:

pool[C/8 bits]: 45

allocated (0 failed), 46800 bytes {3 refcount}

3 active IPv4 tables out of a maximum of 2048

VRF

Prefixes Memory Flags

Default

38 23620

cust-one

11 14680 LCS

cust-one-ipv4

11 14680 LCS

1 active IPv6 table out of a maximum of 1

VRF

Prefixes Memory Flags

Default

0 60

london#show cef table

IPv4 cust-one

Table: IPv4:cust-one (id 1)

ref count:

3

reset count:

1

flags (0x01):

LCS

smp allowed:

yes

default network:

none

route count:

11

route count (fwd):

11

route count (non-fwd)

: 0

Database epoch: 8 (11

entries at this epoch)

Subblocks:

None

london#show cef table

IPv4 Default

Table: IPv4:Default (id 0)

ref count:

17

reset count:

1

flags (0x00):

none

smp allowed:

yes

default network:

0.0.0.0/0

route count:

38

route count (fwd):

38

Example 6-15 show cef Commands route count (non-fwd): 0

Database epoch: 7 (38 entries at this epoch) Subblocks: None

The clear cef table {IPv4 | IPv6 {vrf {vrf-name I*}}} command rebuilds the CEF table. On a 12000 series router, you could use the command clear cef linecard [slot-number] [adjacency I interface I prefix I events] to resend the CEF table from the Router Processor board to the line cards, as shown in Example 6-16.

Example 6-16 clear cef Commands

london#clear

cef ?

interface

CEF interface information

linecard

CEF information related to linecard

table

CEF forwarding table

london#clear

cef table IPv4 vrf ?

*

All VRFs

Default

cust-one

cust-one-ipv4

london#clear

cef linecard ?

<0-37>

linecard slot number

Adjacency

Clear adjacency information

Interface

Clear interface related information

Prefix

Clear Cisco Express Forwarding table

events

Clear the linecard event log

<cr>

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