Catalyst 6500 Series Software Configuration Guide, 8.7
Configuring aCEF
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Table Of Contents

Configuring aCEF

Understanding How aCEF Works

aCEF Configuration Guidelines and Restrictions

Configuring aCEF

Configuring Non-Switch Flows

Configuring Aging Parameters

show commands

show mls accelerated-cef aging

show mls accelerated-cef entries

show mls accelerated-cef non-switched-flows

show mls accelerated-cef summary


Configuring aCEF

This chapter describes how to configure Accelerated Cisco Express Forwarding (aCEF) which requires the following hardware components:

•Supervisor Engine 720 with the integrated 720Gbps switch fabric

•Supported switching modules:

–48-port 10/100/1000BASE-TX (WS-X6748-GE-TX)

–24-port 1000BASEX (WS-X6724-SFP)

–48 port-1000BASEX (WS-X6748-SFP)

–4-port 10-Gigabit Ethernet (WS-X6704-10GE)

Note For complete information on the syntax and usage information for the supervisor engine commands that are used in this chapter, refer to the Catalyst 6500 Series Command Reference publication.

This chapter consists of these sections:

•Understanding How aCEF Works

•aCEF Configuration Guidelines and Restrictions

•Configuring aCEF

Understanding How aCEF Works

The aCEF-supported switching modules utilize cache-based forwarding to reduce lookup overhead on the supervisor engine PFC3. The cache-based forwarding significantly improves forwarding performance.

aCEF Configuration Guidelines and Restrictions

This section describes the guidelines and restrictions for configuring aCEF:

•With aCEF-supported switching modules, there are only two switching modes:

–Truncated mode (at least one nonfabric-enabled module is installed)

–Compact mode (no nonfabric-enabled modules are installed)

•Remote (console) access to aCEF-supported switching modules from the supervisor engine is not supported.

•The only MLS flow mask supported is full flow. Full flow is the most-specific flow mask. A full flow entry includes the destination/source IP address, destination/source Layer 4 port number, protocol type, and Layer 2 header.

Configuring aCEF

All the show and set commands can be entered at the module level, module/port level, or at the system (global) level. A command entered at the system level is applied to all installed aCEF-supported switching modules. However, because multiple ports on a module are controlled by one ASIC, granularity down to an individual port is not supported. If you use the module/port level to change the configuration of a single port on a module, all the module ports get the configuration change.

The module/port level configuration takes precedence over the module level configuration, and the module level configuration takes precedence over the system level configuration.

These sections describe how to configure aCEF:

•Configuring Non-Switch Flows

•Configuring Aging Parameters

•show commands

Configuring Non-Switch Flows

The non-switch-flow configuration option can be used to designate IP version 4 flows that you do not want to be switched (cached) by the aCEF-supported switching modules. You use the no-switch-flow option to designate flows that are not making efficient usage of the cache. Use the any keyword to ignore certain parameters. The command syntax is as follows: 

Console> (enable) set mls accelerated-cef 3 non-switch-flow ?

  ipv4                       IPv4 flows

Console> (enable) set mls accelerated-cef 3 non-switch-flow ipv4 ?

  <vlan>                     VLAN number

  any                        Any Vlan

Console> (enable) set mls accelerated-cef 3 non-switch-flow ipv4 any ?

  <ip/mask>                  Source IP/Mask

  any                        Any source IP/Mask

Console> (enable) set mls accelerated-cef 3 non-switch-flow ipv4 1 ? 

  <ip/mask>                  Source IP/Mask

  any                        Any source IP/Mask

Console> (enable) set mls accelerated-cef 3 non-switch-flow ipv4 1 any ?

  <ip/mask>                  Destination IP/Mask

  any                        Any destination IP/Mask

Console> (enable)

Configuring Aging Parameters

The state and identity of flows are maintained by the aCEF-supported switching modules cache while packet traffic is active; when traffic for a flow ceases, the entry ages out. You can configure the aging time for entries that are kept in the cache. If an entry is not used for the specified period of time, the entry ages out. Normal and aggressive aging are supported. Aggressive aging can be turned on to improve performance. The aggressive-aging monitor-time period and packet-rate thresholds can also be configured.

The command syntax is as follows: 

Console> (enable) set mls accelerated-cef aging ?

  aggressive  aggressive aging parameters to improve accelerated-cef performance

  normal      normal aging


Console> (enable) set mls accelerated-cef aging normal ?

  <1-1024>  aging time in seconds (default is 16 secs)


Console> (enable) set mls accelerated-cef aging normal 100 ?

  <cr>


Console> (enable) set mls accelerated-cef aging aggressive ?

  disable         Disable aggressive aging

  interval        Time interval to monitor accelerated CEF usage to trigger

                  aggressive aging (default is 5 secs)

  pkt-rate-range  packet rates to age out accelerated CEF entries

  threshold       Accelerated CEF utilization % to trigger aggressive aging

                  (default is 75 %)


Console> (enable) set mls accelerated-cef aging aggressive disable ?

  <cr>


Console> (enable) set mls accelerated-cef aging aggressive interval ?

  <1-100>  Time interval in secs


Console> (enable) set mls accelerated-cef aging aggressive interval 10 ?

  <cr>


Console> (enable) set mls accelerated-cef aging aggressive pkt-rate-range ?

  start-rate  Starting pkt rate - entries with lower rate will be aged out


Console> (enable) set mls accelerated-cef aging aggressive pkt-rate-range start-rate ?

  <0-1024>  Starting pkt rate per second - default is 0 pkt/sec


Console> (enable) set mls accelerated-cef aging aggressive pkt-rate-range start-rate 100 ?

  end-rate  Ending pkt rate to be used by the ager - (increments from the

            start-rate till this rate)


Console> (enable) set mls accelerated-cef aging aggressive pkt-rate-range start-rate 100 
end-rate ?

  <0-65536>  End pkt rate per second - default is 8 pkt/sec


Console> (enable) set mls accelerated-cef aging aggressive pkt-rate-range start-rate 100 
end-rate 1000 ?

  <cr>


Console> (enable) set mls accelerated-cef aging aggressive threshold ?

  <50-99>  utilization range


Console> (enable) set mls accelerated-cef aging aggressive threshold 80 ?

  <cr>

show commands

The command syntax is as follows: 

Console> (enable) show mls accelerated-cef ?

  <mod>                      Module number

  <mod/port>                 Module number and Port number(s)

  aging                      Aging summary

  entries                    Entries

  non-switched-flows         Flows that are not switched on Accelerated CEF

  summary                    Summary for the system

Console> (enable) show mls accelerated-cef 3 ?

  aging                      Aging summary

  entries                    Entries

  non-switched-flows         Flows that are not switched on Accelerated CEF

  summary                    Summary for the system

Console> (enable) show mls accelerated-cef 3/1 ?

  aging                      Aging summary

  entries                    Entries

  non-switched-flows         Flows that are not switched on Accelerated CEF

  summary                    Summary for the system

The following sections provide a sampling of the show commands:

•show mls accelerated-cef aging

•show mls accelerated-cef entries

•show mls accelerated-cef non-switched-flows

•show mls accelerated-cef summary

show mls accelerated-cef aging 

Console> (enable) show mls accelerated-cef aging


Aging summary for Module 3, Ports 1, 3, 5 ... 47

------------------------------------------------

  Aging configuration: 

    Normal aging time = 16 secs

    Aggressive aging:

      threshold usage to trigger aggressive aging = 75 %

      Accelerated CEF usage monitor interval = 10 secs

      Packet range for aggressive aging = 0 .. 8 pkts/sec

  Current aging state = Normal


Aging summary for Module 3, Ports 2, 4, 6 ... 48

------------------------------------------------

  Aging configuration: 

    Normal aging time = 16 secs

    Aggressive aging:

      threshold usage to trigger aggressive aging = 75 %

      Accelerated CEF usage monitor interval = 10 secs

      Packet range for aggressive aging = 0 .. 8 pkts/sec

  Current aging state = Normal

Console> (enable)

show mls accelerated-cef entries 

Console> (enable) show mls accelerated-cef entries ipv4 


Accelerated CEF entries for Module 3, Ports 1, 3, 5 ... 47

----------------------------------------------------------


Accelerated CEF Entry addr=64:

-------------------------------

  Flow key:

   flow_type=IPv4  module/port=3/27 source_vlan=1

   smac=00-00-00-00-00-97  dmac=00-00-00-00-00-95

   ip_src=10.7.41.101 ip_dst=10.6.41.101

   protocol=0(other) 

  Flow mask memory:

    reaffirmation_period=512 msec, reaffirmation_pkt_count=1024

    Flow Mask is Accelerated CEF full flow


Accelerated CEF Entry addr=79:

-------------------------------

  Flow key:

   flow_type=IPv4  module/port=3/27 source_vlan=1

   smac=00-00-00-00-00-97  dmac=00-00-00-00-00-95

   ip_src=10.7.41.110 ip_dst=10.6.41.110

   protocol=0(other) 

  Flow mask memory:

    reaffirmation_period=512 msec, reaffirmation_pkt_count=1024

    Flow Mask is Accelerated CEF full flow

.

.

.

Console> (enable)

show mls accelerated-cef non-switched-flows 

Console> (enable) show mls accelerated-cef 3 non-switched-flows 


Non switched flows for Module 3, Ports 1, 3, 5 ... 47

-----------------------------------------------------


Non switched flows for Module 3, Ports 2, 4, 6 ... 48

-----------------------------------------------------


Console> (enable) show mls accelerated-cef 3 non-switched-flows ipv4 


Non switched flows for Module 3, Ports 1, 3, 5 ... 47

-----------------------------------------------------

idx vlan    source IP     destination IP  protocol  src_port dst_port tcp_info

--- ---- --------------- --------------- ---------- -------- -------- --------

  1    *               *               *       icmp        *        *        0

  2    *               *               *        udp        *   domain        0

  3    *               *               *        udp        *      ntp        0

  4    *               *               *        tcp        *     smtp        0

  5    *               *               *        tcp        *        *   1(FIN)

  6    *               *               *        tcp        *        *   4(RST)

  7    1     10.7.41.128               *          *

  8    1     10.7.41.116               *          *


Non switched flows for Module 3, Ports 2, 4, 6 ... 48

-----------------------------------------------------

idx vlan    source IP     destination IP  protocol  src_port dst_port tcp_info

--- ---- --------------- --------------- ---------- -------- -------- --------

  1    *               *               *       icmp        *        *        0

  2    *               *               *        udp        *   domain        0

  3    *               *               *        udp        *      ntp        0

  4    *               *               *        tcp        *     smtp        0

  5    *               *               *        tcp        *        *   1(FIN)

  6    *               *               *        tcp        *        *   4(RST)

  7    1     10.7.41.128               *          *

  8    1     10.7.41.116               *          *

show mls accelerated-cef summary 

Console> (enable) show mls accelerated-cef summary 


Accelerated CEF Summary for Module 3, Ports 1, 3, 5 ... 47

----------------------------------------------------------

  Accelerated CEF size = 8 K

  Total number of flows = 27

     Total IPv4 flows = 27

     Total IPv6 flows = 0

     Total number of packets forwarded by Accelerated CEF = 13839862646


  IPV4 Default Flow Mask Memory : 

    reaffirmation_period=512 msec, reaffirmation_pkt_count=1024

    Flow Mask is Accelerated CEF full flow


  IPv6 Default Flow Mask Memory : 

    reaffirmation_period=512 msec, reaffirmation_pkt_count=1024

    Flow Mask is Accelerated CEF full flow


  List of default accelerated-cef non-switched ipv4 flows:

    DNS    ICMP    SMTP    NTP    TCP-FIN    TCP-RST

  List of default accelerated-cef non-switched ipv6 flows:

    TCP-FIN    TCP-RST



Accelerated CEF Summary for Module 3, Ports 2, 4, 6 ... 48

----------------------------------------------------------

  Accelerated CEF size = 8 K

  Total number of flows = 0

     Total IPv4 flows = 0

     Total IPv6 flows = 0

     Total number of packets forwarded by Accelerated CEF = 0


  IPV4 Default Flow Mask Memory : 

    reaffirmation_period=512 msec, reaffirmation_pkt_count=1024

    Flow Mask is Accelerated CEF full flow


  IPv6 Default Flow Mask Memory : 

    reaffirmation_period=512 msec, reaffirmation_pkt_count=1024

    Flow Mask is Accelerated CEF full flow


  List of default accelerated-cef non-switched ipv4 flows:

    DNS    ICMP    SMTP    NTP    TCP-FIN    TCP-RST

  List of default accelerated-cef non-switched ipv6 flows:

    TCP-FIN    TCP-RST


Console> (enable) show mls accelerated-cef summary protocol 


Protocol based summary for Module 3, Ports 1, 3, 5 ... 47

---------------------------------------------------------


 Protocol    Port    Total flows

 --------    ----    -----------

      tcp  telnet              0

      tcp     www              0

      tcp     ftp              0

      tcpftp-data              0



Protocol based summary for Module 3, Ports 2, 4, 6 ... 48

---------------------------------------------------------


 Protocol    Port    Total flows

 --------    ----    -----------

      tcp  telnet              0

      tcp     www              0

      tcp     ftp              0

      tcpftp-data              0


Console> (enable)