Cisco Systems IC-23 User Manual
Configuring LAN Interfaces
Use the information in this chapter to configure LAN interfaces supported on Cisco routers and access
servers.
This chapter describes the processes for configuring LAN interfaces in the following sections:
• Configuring an Ethernet or Fast Ethernet Interface
• Configuring Fast EtherChannel
• Configuring a Fiber Distributed Data Interface
• Configuring a Hub Interface
• Configuring a LAN Extender Interface
• Configuring a Token Ring Interface
For examples of configuration tasks, see the “LAN Interface Configuration Examples” section.
For hardware technical descriptions and information about installing interfaces, refer to the hardware
installation and configuration publication for your product. For a complete description of the LAN
interface commands used in this chapter, refer to the “Interface Commands” chapter of the Cisco IOS
Interface Command Reference. To locate documentation of other commands that appear in this chapter,
use the command reference master index or search online.
Configuring an Ethernet or Fast Ethernet Interface
Cisco supports both 10-Mbps Ethernet and 100-Mbps Fast Ethernet.
Support for the 10-Mbps and 100-Mbps Ethernet interface is supplied on various Ethernet network
interface cards or systems.
The Fast Ethernet NP-1FE module, for example, provides the following benefits:
• VLAN routing—Virtual LAN (VLAN) support enables network managers to group users logically
rather than by physical location. The high performance of the underlying Cisco 4700, combined
with the feature-rich NP-1FE, makes it an ideal combination for a low-density, higher-performance
application such as inter-VLAN routing.
• High-speed interconnections—The Fast Ethernet interface enables network managers to implement
Fast-Ethernet routing solutions for optimal cost and performance across a wide range of
applications, including campus or enterprise backbones and data centers. It is also a low-cost way
to provide Fast-Ethernet access to traditional low-speed WAN services.
• Local area network aggregation—The Cisco 4500 or the Cisco 4700 series routers can support as
many as 12 Ethernet, 4 Token Ring, or 1 FDDI segment. ISDN interfaces are also supported.
Cisco IOS Interface Configuration Guide
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Configuring an Ethernet or Fast Ethernet Interface
With the Catalyst 3000 or Catalyst 5000 system, the Fast Ethernet processor can be used to
aggregate up to twelve 10-Mbps LANs and give them high-speed access to such Layer 3 routing
services as providing firewalls and maintaining access lists.
Cisco 7200 series routers support an I/O controller with an RJ-45 interface. You can configure the
optional Fast Ethernet port for use at 100-Mbps full-duplex or half-duplex operation (half duplex is the
default). The Fast Ethernet port is equipped with either a single MII receptacle or an MII receptacle and
an RJ-45 receptacle. To support this new feature, the media-type interface command has been modified.
The media-type interface command now supports two options:
• 100basex—Specifies an RJ-45 100BASE-X physical connection.
• mii—Specifies a media-independent interface.
Second-generation Fast Ethernet Interface Processors (FEIP2-DSW-2TX and FEIP2-DSW-2FX) are
available on Cisco 7500 series routers and on Cisco 7000 series routers with the 7000 Series Route
Switch Processor (RSP7000) and 7000 Series Chassis Interface (RSP7000CI). The FEIP2-DSW is a
dual-port, fixed-configuration interface processor that provides two 100-Mbps Fast Ethernet (FE)
interfaces. Each interface on the FEIP2-DSW supports half-duplex only for a maximum aggregate
bandwidth of 200 Mbps.
Refer to the Cisco Product Catalog for specific platform and hardware compatibility information.
Use the show interfaces, show controllers mci, and show controllers cbus EXEC commands to display
the Ethernet port numbers. These commands provide a report for each interface supported by the router
or access server.
Use the show interface fastethernet command to display interface statistics, and use the show
controller fastethernet to display the information about the Fast Ethernet controller chip. The output
shows statistics, including information about initialization block information, transmit ring, receive ring
and errors.
Configuring LAN Interfaces
For information on how to configure Fast EtherChannel, see the tasks listed in the “Configuring Fast
EtherChannel” section.
Ethernet and Fast Ethernet Interface Configuration Task List
Perform the tasks in the following sections to configure features on an Ethernet or Fast Ethernet
interface:
• Specifying an Ethernet or Fast Ethernet Interface (Required)
• Specifying an Ethernet Encapsulation Method (Optional)
• Specifying Full-Duplex Operation (Optional)
• Specifying the Media and Connector Type (Optional)
• Extending the 10BASE-T Capability (Optional)
• Configuring Fast Ethernet 100BASE-T (Optional)
• Configuring PA-12E/2FE Port Adapter (Optional)
• Configuring the 100VG-AnyLAN Port Adapter (Optional)
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Cisco IOS Interface Configuration Guide
Configuring LAN Interfaces
Specifying an Ethernet or Fast Ethernet Interface
To specify an Ethernet interface and enter interface configuration mode, use one of the following
commands in global configuration mode:
Command Purpose
interface ethernet number
interface ethernet slot/port
interface ethernet
slot/port-adapter/port
interface fastethernet number
interface fastethernet slot/port
interface fastethernet
slot/port-adapter/port
Begins interface configuration.
Begins interface configuration for the Cisco 7200 and Cisco 7500 series
routers.
Begins interface configuration for Cisco 7500 series routers.
Begins interface configuration for the Cisco 4000 series with a Fast Ethernet
NIM installed.
Specifies a Fast Ethernet interface and enters interface configuration mode on
the Cisco 7200 series routers.
Specifies a Fast Ethernet interface and enters interface configuration mode on
the Cisco 7500 series routers.
Configuring an Ethernet or Fast Ethernet Interface
Use the show interfaces fastethernet command to display the Fast Ethernet slots and ports. The Fast
Ethernet NIM and the FEIP default to half-duplex mode.
Specifying an Ethernet Encapsulation Method
Currently, there are three common Ethernet encapsulation methods:
• The standard ARPA Ethernet Version 2.0 encapsulation, which uses a 16-bit protocol type code
(the default encapsulation method)
• SAP IEEE 802.3 encapsulation, in which the type code becomes the frame length for the IEEE 802.2
LLC encapsulation (destination and source Service Access Points, and a control byte)
• The SNAP method, as specified in RFC 1042, “Standard for the Transmission of IP Datagrams Over
IEEE 802 Networks,” which allows Ethernet protocols to run on IEEE 802.2 media
The encapsulation method you use depends upon the routing protocol you are using, the type of Ethernet
media connected to the router or access server, and the routing or bridging application you configure.
Establish Ethernet encapsulation of IP packets by using one of the following commands in interface
configuration mode:
Command Purpose
encapsulation arpa
encapsulation sap
encapsulation snap
Selects ARPA Ethernet encapsulation.
Selects SAP Ethernet encapsulation.
Selects SNAP Ethernet encapsulation.
For an example of selecting Ethernet encapsulation for IP, see the “Ethernet Encapsulation Enablement
Example” section.
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Configuring an Ethernet or Fast Ethernet Interface
Specifying Full-Duplex Operation
The default is half-duplex mode on the FEIP2-DSW-2FX. To enable full-duplex mode on the
FEIP2-DSW-2FX (for a maximum aggregate bandwidth of 200 Mbps), use either of the following
commands in interface configuration mode:
Command Purpose
full-duplex
or
no half-duplex
For an example to enable full-duplex mode on Fast Ethernet, see the “Full Duplex Enablement Operation
Example” section.
Caution To prevent system problems, do not configure both FEIP2-DSW-2FX interfaces for
full-duplex operation at the same time.
Enables full-duplex on the Fast Ethernet interface of the FEIP2-DSW-2FX.
Configuring LAN Interfaces
Note The FEIP2-DSW-2TX supports half-duplex only and should not be configured for
full-duplex.
Specifying the Media and Connector Type
You can specify that the Ethernet network interface module (NIM) on the Cisco 4000 series routers use
either the default of an AUI and a 15-pin connector, or 10BASE-T and an RJ-45 connector. To do so, use
one of the following commands in interface configuration mode:
Command Purpose
media-type aui
media-type 10baset
The default media connector type is an RJ-45 or SC (fiber-optic) connector. You can specify that the
interface uses either an MII connector, or an RJ-45 or SC (fiber-optic) connector (this is the default). To
do so, use one of the following commands in interface configuration mode:
Command Purpose
media-type mii
media-type 100basex
Selects a 15-pin Ethernet connector.
Selects an RJ-45 Ethernet connector.
Selects an MII Ethernet connector.
Selects an RJ-45 Ethernet connector for the FEIP2-DSW-2TX or an SC
connector for the FEIP2-DSW-2FX.
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Note When using the I/O controller that is equipped with an MII receptacle and an RJ-45
receptacle, only one receptacle can be configured for use at a time.
Cisco IOS Interface Configuration Guide
Configuring LAN Interfaces
Extending the 10BASE-T Capability
On a Cisco 4000 series or Cisco 4500 series routers, you can extend the twisted-pair 10BASE-T capability
beyond the standard 100 meters by reducing the squelch (signal cutoff time). This feature applies only
to the LANCE controller 10BASE-T interfaces. LANCE is the AMD controller chip for the Cisco 4000
and Cisco 4500 Ethernet interface.
Note Does not apply to the Fast Ethernet interface.
To reduce squelch, use the first command in the following table in interface configuration mode. You
can later restore the squelch by using the second command.
Command Purpose
squelch reduced
squelch normal
Reduces the squelch.
Returns squelch to normal.
Configuring an Ethernet or Fast Ethernet Interface
Configuring Fast Ethernet 100BASE-T
You must configure the Fast Ethernet 100BASE-T interface on a Cisco AS5300 so that it can be
recognized as a device on the Ethernet LAN. The Fast Ethernet interface supports 10- and 100-Mbps
speeds with the 100BASE-T and 10BASE-T routers, hubs, and switches.
To configure the interface, use the following commands beginning in privileged EXEC mode:
Command Purpose
Step 1
Step 2
Step 3
Step 4
Step 5
configure terminal
interface fastethernet number
ip address address subnet-mask
speed {10 | 100 | auto}
duplex {full | half | auto}
1. The auto option automatically negotiates the speed based on the speed and the peer router, hub, or switch media.
To use the auto-negotiation capability (that is, to detect speed and duplex modes automatically), you
must set both speed and duplex to auto. Setting the speed to auto negotiates speed only, and setting
duplex to auto negotiates duplex only. Table 3 describes the access server’s performance for different
combinations of the duplex and speed command options. The specified duplex command option plus
the specified speed command option produces the resulting system action.
Enters global configuration mode.
Enters Fast Ethernet interface configuration mode.
Assigns an IP address and subnet mask to the interface.
Assigns a speed to the interface. The default is 100 Mbps.
1
For relationship between duplex and speed command options, see Table 3.
Sets up the duplex configuration on the Fast Ethernet interface. The default
is half duplex.
1
For relationship between duplex and speed command options, see Table 3.
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Configuring an Ethernet or Fast Ethernet Interface
Table 3 Relationship Between Duplex and Speed Command Options
Duplex Command Speed Command Resulting System Actions
duplex auto speed auto
duplex auto speed 100 or speed 10
duplex half
or
duplex full
duplex half speed 10
duplex full speed 10
duplex half speed 100
duplex full speed 100
speed auto
Configuring LAN Interfaces
Autonegotiates both speed and
duplex modes.
Autonegotiates both speed and
duplex modes.
Autonegotiates both speed and
duplex modes.
Forces 10 Mbps and half duplex.
Forces 10 Mbps and full duplex.
Forces 100 Mbps and half
duplex.
Forces 100 Mbps and full
duplex.
Configuring PA-12E/2FE Port Adapter
The PA-12E/2FE Ethernet switch port adapter provides Cisco 7200 series routers with up to twelve
10-Mbps and two 10/100-Mbps switched Ethernet (10BASE-T) and Fast Ethernet (100BASE-TX)
interfaces for an aggregate bandwidth of 435 Mbps, full-duplex. The PA-12E/2FE port adapter supports
the Ethernet, IEEE 802.3, and IEEE 802.3u specifications for 10-Mbps and 100-Mbps transmission over
UTP cables.
The PA-12E/2FE port adapter offloads Layer 2 switching from the host CPU by using store-and-forward
or cut-through switching technology between interfaces within the same virtual LAN (VLAN) on the
PA-12E/2FE port adapter. The PA-12E/2FE port adapter supports up to four VLANs (bridge groups).
Note The PA-12E/2FE port adapter is a dual-width port adapter, which means it occupies two
horizontally aligned port adapter slots when installed in a Cisco 7200 series router.
(Single-width port adapters occupy individual port adapter slots in a Cisco 7200 series
router.)
All interfaces on the PA-12E/2FE port adapter support autosensing and autonegotiation of the proper
transmission mode (half-duplex or full-duplex) with an attached device. The first two PA-12E/2FE
interfaces (port 0 and port 1) also support autosensing and autonegotiation of the proper connection
speed (10-Mbps or 100-Mbps) with an attached device. If an attached device does not support
autosensing and autonegotiation of the proper transmission mode, the PA-12E/2FE interfaces attached
to the device automatically enter half-duplex mode. Use the show system:running-config command to
determine if a PA-12E/2FE interface is autosensing and autonegotiating the proper transmission mode
with an attached device. Use the full-duplex and the half-duplex commands to change the transmission
mode of a PA-12E/2FE interface. After changing the transmission mode, use the show interfaces
command to verify the interface’s transmission mode.
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Cisco IOS Interface Configuration Guide
Configuring LAN Interfaces
Note If you use the full-duplex and the half-duplex commands to change the transmission mode
Note If you plan to use a PA-12E/2FE interface to boot from a network (using TFTP), ensure that
Configuring an Ethernet or Fast Ethernet Interface
of the first two PA-12E/2FE interfaces (port 0 and port 1), the transmission speed of the two
PA-12E/2FE interfaces automatically defaults to 100-Mbps. The first two PA-12E/2FE
interfaces only operate at 10-Mbps when the interfaces are autosensing and autonegotiating
the proper connection speed (10-Mbps or 100-Mbps) with an attached device.
To configure the PA-12E/2FE port adapter, perform the tasks in the following sections:
• Configuring the PA-12E/2FE Port Adapter (Required)
• Monitoring and Maintaining the PA-12E/2FE Port Adapter (Optional)
• Configuring Bridge Groups Using the 12E/2FE VLAN Configuration WebTool (Optional)
the interface is configured for a loop-free environment, an IP address is configured for the
interface’s bridge-group virtual interface, and system boot image 11.2(10)P is installed on
your router (use the show version command to view your router’s system boot image).
Then, before booting from the network server, use the bridge-group bridge-group number
spanning-disabled command to disable the Spanning-Tree Protocol configured on the
interface to keep the TFTP server from timing out and closing the session.
For detailed information about booting from a network using TFTP, loading a system image
from a network server, and configuring the Spanning-Tree Protocol on your Cisco 7200
series router, refer to the PA-12E/2FE Ethernet Switch Port Adapter book that accompanies
the hardware and to the Cisco IOS Bridging and IBM Networking Configuration Guide.
For information on other commands that can be used to configure a PA-12E/2FE port adapter, refer to
the “Interfaces Commands” chapter in the Cisco IOS Interface Command Reference. For information on
bridging, refer to the “Configuring Transparent Bridging” chapter in the Cisco IOS Bridging and IBM
Networking Configuration Guide.
For PA-12E/2FE port adapter configuration examples, see the “PA-12E/2FE Port Configuration
Examples” section.
Configuring the PA-12E/2FE Port Adapter
This section provides instructions for a basic configuration. You might also need to enter other
configuration commands depending on the requirements for your system configuration and the protocols
you plan to route on the interface. For complete descriptions of configuration commands and the
configuration options available, refer to the other configuration guides in the Cisco IOS documentation
set.
Cisco IOS Interface Configuration Guide
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Configuring an Ethernet or Fast Ethernet Interface
To configure the interfaces on the PA-12E/2FE port adapter, use the following commands in global
configuration mode:
Command Purpose
Step 1
Step 2
bridge bridge-group protocol ieee
interface fastethernet slot/port
(ports 0 and 1)
interface ethernet slot/port
(ports 2 through 13)
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
bridge-group bridge-group
cut-through [receive | transmit]
full-duplex
no shutdown
exit
copy system:running-config
nvram:startup-config
Configuring LAN Interfaces
Specifies the type of Spanning-Tree Protocol.
The PA-12E/2FE port adapter supports DEC and IEEE Spanning-Tree
Protocols; however, we recommend using the IEEE protocol when
configuring bridge groups.
Enters the interface you want to configure.
Assigns a bridge group to the interface.
(Optional) Configures the interface for cut-through switching technology.
The default is store-and-forward (that is, no cut-through).
(Optional) Configures the transmission mode for full-duplex, if an attached
device does not support autosensing or autonegotiation. The default is
half-duplex.
Restarts the interface.
Returns to configuration mode.
Repeat Steps 1 through 7 for each interface.
Saves the new configuration to memory.
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
To enable integrated routing and bridging on the bridge groups, use the following commands beginning
in global configuration mode:
Command Purpose
bridge irb
interface bvi bridge-group
ip address address mask
Enables integrated routing and bridging.
Enables a virtual interface on a bridge group.
Assigns an IP address and subnet mask to the bridge-group virtual
interface.
no shutdown
exit
Restarts the interface.
Returns to configuration mode.
Repeat Steps 1 through 5 for each bridge group.
bridge bridge-group route
protocol
exit
copy system:running-config
nvram:startup-config
Specifies the protocol for each bridge group.
Exits configuration mode.
Saves the new configuration to memory.
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Cisco IOS Interface Configuration Guide
Configuring LAN Interfaces
Monitoring and Maintaining the PA-12E/2FE Port Adapter
After configuring the new interface, you can display its status and verify other information. To display
information about the PA-12E/2FE port adapter, use the following commands in EXEC mode:
Command Purpose
show version
Displays the configuration of the system hardware, the software version,
the names and sources of configuration files, and the boot image.
show controllers
show interface fastethernet slot/port
(ports 0 and 1)
Displays all current port adapters and their interfaces
Displays the interfaces so you can verify that they have the correct slot
number and that the interface and line protocol are in the correct state.
or
show interface ethernet slot/port
(ports 2 through 13)
show bridge group
show interface ethernet slot/port irb
(ports 2 through 13)
Displays all bridge groups and their interfaces.
Displays the routed protocol so you can verify that it is configured
correctly for each interface.
Configuring an Ethernet or Fast Ethernet Interface
or
show interface fastethernet slot/port irb
(ports 0 and 1)
show protocols
Displays the protocols configured for the entire system and specific
interfaces.
show pas eswitch addresses fastethernet
slot/port
Displays the Layer 2 learned addresses for each interface.
(ports 0 and 1)
or
show pas eswitch addresses ethernet
slot/port
(ports 2 through 13)
more system:running-config
more nvram:startup-config
Displays the running configuration file.
Displays the configuration stored in NVRAM.
Configuring Bridge Groups Using the 12E/2FE VLAN Configuration WebTool
The 12E/2FE VLAN Configuration WebTool, shown in Figure 2, is a web browser-based Java applet that
displays configured interfaces and bridge groups for PA-12E/2FE port adapters installed in Cisco
routers. With the WebTool you can perform the following tasks:
• Create and delete bridge groups (also referred to as VLANs)
• Add and remove PA-12E/2FE interfaces from bridge groups
• Assign colors to bridge groups and PA-12E/2FE interfaces
• Administratively shut down (disable) and bring up (enable) PA-12E/2FE interfaces
• View the bridge-group status of each PA-12E/2FE interface
Cisco IOS Interface Configuration Guide
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Configuring an Ethernet or Fast Ethernet Interface
You can access the 12E/2FE VLAN Configuration WebTool from your router’s home page. For complete
procedures on how to use the VLAN Configuration WebTool, refer to the PA-12E/2FE Ethernet Switch
Port Adapter book that accompanies the hardware.
Figure 2 Example Home Page for a Cisco 7200 Series Router (Cisco 7206 Shown)
Configuring LAN Interfaces
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All Cisco routers running Cisco IOS Release 11.0 or later have a home page. All Cisco router home
pages are password protected. Contact your network administrator if you do not have the name or
password for your Cisco 7200 series router.
If your router has an installed PA- 12E/2FE port adapter, the 12E/2FE VLAN Configuration WebTool
shown in Figure 2 can be accessed from the router’s home page using a Java-enabled web browser.
Cisco IOS Interface Configuration Guide
Configuring LAN Interfaces
Configuring the 100VG-AnyLAN Port Adapter
The 100VG-AnyLAN port adapter (PA-100VG) is available on Cisco 7200 series routers and on
Cisco 7500 series routers.
The PA-100VG provides a single interface compatible with and specified by IEEE 802.12 to support
100 Mbps over Category 3 or Category 5 unshielded twisted-pair (UTP) cable with RJ-45 terminators.
The PA-100VG supports 802.3 Ethernet packets and can be monitored with the IEEE 802.12 Interface
MIB.
To configure the PA-100VG port adapter, use the following commands beginning in global configuration
mode:
Command Purpose
Step 1
Step 2
Step 3
interface vg-anylan
slot/port-adapter/port
(Cisco 7500)
or
interface vg-anylan slot/port
(Cisco 7200)
ip address ip-address mask
frame-type ethernet
Configuring Fast EtherChannel
Specifies a 100VG-AnyLAN interface and enters interface
configuration.
Specifies the IP address and subnet mask to the interface.
Configures the frame type. Currently, only Ethernet frames are
supported. The frame type defaults to Ethernet.
Note The port number for the 100VG-AnyLAN port adapter is always 0.
Configuring the PA-100VG interface is similar to configuring an Ethernet or Fast Ethernet interface. To
display information about the 100VG-AnyLAN port adapter, use the show interfaces vg-anylan EXEC
command.
Configuring Fast EtherChannel
The Fast EtherChannel feature allows multiple Fast Ethernet point-to-point links to be bundled into one
logical link to provide bidirectional bandwidth of up to 800 Mbps. Fast EtherChannel builds on
standards-based 802.3 full-duplex Fast Ethernet to provide fault-tolerant, high-speed links between
switches, routers, and servers. This feature can be configured between Cisco 7500 series routers and
Cisco 7000 series routers with the 7000 Series Route Switch Processor (RSP7000) and 7000 Series
Chassis Interface (RSP7000CI) or between a Cisco 7500 series router or a Cisco 7000 series router with
the RSP7000 and RSP700CI and a Catalyst 5000 switch.
Note Using the Fast EtherChannel feature on a Catalyst 5000 switch requires a hardware
upgrade. Contact your local sales representative for upgrade details.
Fast EtherChannel provides higher bidirectional bandwidth, redundancy, and load sharing. Up to four
Fast Ethernet interfaces can be bundled in a port-channel, and the router or switch can support up to four
port-channels. The Fast EtherChannel feature is capable of load balancing traffic across the Fast Ethernet
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Configuring Fast EtherChannel
links. Unicast, broadcast, and multicast traffic is distributed across the links providing higher
performance and redundant parallel paths. In the event of a link failure, traffic is redirected to remaining
links within the Fast EtherChannel without user intervention.
In this release of the Fast EtherChannel feature, IP traffic is distributed over the port-channel interface
while traffic from other routing protocols is sent over a single link. Bridged traffic is distributed based
on the Layer 3 information in the packet. If the Layer 3 information does not exist in the packet, the
traffic is sent over the first link.
Fast EtherChannel supports all features currently supported on the Fast Ethernet interface. You must
configure these features on the port-channel interface rather than on the individual Fast Ethernet
interfaces. Fast EtherChannel connections are fully compatible with Cisco IOS virtual LAN (VLAN)
and routing technologies. The Inter-Switch Link (ISL) VLAN trunking protocol can carry multiple
VLANs across a Fast EtherChannel, and routers attached to Fast EtherChannel links can provide full
multiprotocol routing with support for host standby using Host Standby Router Protocol (HSRP).
The port-channel (consisting of up to four Fast Ethernet interfaces) is treated as a single interface.
Port-channel is used in the Cisco IOS software to maintain compatibility with existing commands on the
Catalyst 5000 switch. You create the Fast EtherChannel by using the interface port-channel interface
configuration command. You can assign up to four Fast Ethernet interfaces to a port-channel by using
the channel-group interface configuration command.
Fast EtherChannel also supports the following two features:
Configuring LAN Interfaces
• Support for host standby using Host Standby Router Protocol (HSRP)
For more information about configuring HSRP, refer to the “Configuring IP Services” chapter in the
Cisco IOS IP and IP Routing Configuration Guide.
• Support for Cisco Express Forwarding (CEF) and distributed CEF (dCEF)
For more information about configuring CEF, refer to the “Cisco Express Forwarding” chapter in
the Cisco IOS Switching Services Configuration Guide.
For information on how to configure Ethernet or Fast Ethernet, see the tasks listed in the “Configuring
an Ethernet or Fast Ethernet Interface” section.
Fast EtherChannel Configuration Task List
Perform the tasks in the following sections to configure Fast EtherChannel. To configure Fast
EtherChannel, perform the following required steps:
1. Create a port-channel interface and assign an IP address.
2. Assign the Fast Ethernet interfaces (up to four) to the port-channel interface.
For information on other configuration tasks for the Fast EtherChannel, see the “Configuring an Ethernet
or Fast Ethernet Interface” section.
For information on other commands that can be used by the Fast EtherChannel, refer to the other
configuration guides in the Cisco IOS documentation set.
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Cisco IOS Interface Configuration Guide
Configuring LAN Interfaces
Configuring the Port-Channel Interface
To configure the port-channel interface, use the following commands beginning in global configuration
mode:
Command Purpose
Step 1
Step 2
Step 3
Step 4
Step 5
interface port-channel
channel-number
ip address ip-address mask
mac-address ieee-address
end
show interface port-channel
Creates the port-channel interface and enters interface configuration mode. The
channel number can be 1 to 4.
Assigns an IP address and subnet mask to the Fast EtherChannel.
If you configure ISL, you must assign the IP address to the subinterface (for
example, interface port-channel 1.1—an IP address per VLAN) and you must
specify the encapsulation with VLAN number under that subinterface (for
example, encapsulation isl 100).
(Optional) Assigns a static MAC address to the Fast EtherChannel.
If you do not assign a static MAC address on the port-channel interface, the
Cisco IOS software automatically assigns a MAC address. If you assign a static
MAC address and then later remove it, the Cisco IOS software automatically
assigns a MAC address.
(Optional) Enables other supported interface commands to execute, and exits
when they have finished.
Displays information about the port-channel interface so you can verify the
configuration.
Configuring Fast EtherChannel
Note If you want to use the Cisco Discovery Protocol (CDP), you must configure it on the
physical Ethernet, Fast Ethernet, or GigabitEthernet interface, not on the port-channel
interface.
Caution With Release 11.1(20)CC and later, Fast EtherChannel supports CEF/dCEF. We
recommend that you clear all explicit ip route-cache distributed commands from the Fast
Ethernet interfaces before enabling dCEF on the port-channel interface. Doing this gives
the port-channel interface proper control of its physical Fast Ethernet links. When you
enable CEF/dCEF globally, all interfaces that support CEF/dCEF are enabled. When
CEF/dCEF is enabled on the port-channel interface, it is automatically enabled on each of
the Fast Ethernet interfaces in the channel group. However, if you have previously disabled
CEF/dCEF on the Fast Ethernet interface, CEF/dCEF is not automatically enabled. In this
case, you must enable CEF/dCEF on the Fast Ethernet interface.
Cisco IOS Interface Configuration Guide
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Configuring Fast EtherChannel
Configuring the Fast Ethernet Interfaces
To assign the Fast Ethernet interfaces to the Fast EtherChannel, use the following commands beginning
in global configuration mode:
Command Purpose
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
interface fastethernet
slot/port-adapter/port
no ip address
channel-group channel-number
exit
end
show interface port-channel
Creates or modifies an existing Fast Ethernet interface and enters interface
configuration mode.
Disables the IP address before performing the next step, if the Fast Ethernet
interface already exists and has an IP address assigned.
Assigns the Fast Ethernet interfaces to the Fast EtherChannel. The channel
number is the same as the channel number you specified when you created the
port-channel interface.
Exits interface configuration mode. Repeat Steps 1 through 4 to add up to four
Fast Ethernet interfaces to the Fast EtherChannel.
(Optional) Enables other supported interface commands to execute, and exits
when they have finished.
Displays information about the Fast Ethernet interface so you can verify the
configuration.
Configuring LAN Interfaces
Step 1
Step 2
Step 3
Caution The port-channel interface is the routed interface. Do not enable Layer 3 addresses on the
physical Fast Ethernet interfaces. Do not assign bridge groups on the physical Fast Ethernet
interfaces because it creates loops. Also, you must disable spanning tree.
To remove a Fast Ethernet interface from a Fast EtherChannel, use the following commands beginning
in global configuration mode:
Command Purpose
interface fastethernet
slot/port-adapter/port
no channel-group
end
Specifies the Fast Ethernet interface and enters interface configuration mode.
Removes the Fast Ethernet interface from the channel group.
(Optional) Enables other supported interface commands to execute, and exits
when they have finished.
The Cisco IOS software automatically removes a Fast Ethernet interface from the Fast EtherChannel if
the interface goes down, and the software automatically adds the Fast Ethernet interface to the Fast
EtherChannel when the interface is back up.
Currently, Fast EtherChannel relies on keepalives to detect whether the line protocol is up or down.
Keepalives are enabled by default on the Fast Ethernet interfaces. If the line protocol on the interface
goes down because it did not receive a keepalive signal, the Fast EtherChannel detects that the line
protocol is down and removes the interface from the Fast EtherChannel. However, if the line protocol
remains up because keepalives are disabled on the Fast Ethernet interface, the Fast EtherChannel cannot
detect this link failure (other than a cable disconnect) and does not remove the interface from the Fast
IC-36
Cisco IOS Interface Configuration Guide
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