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This chapter describes the basic interface configuration for the Layer 3 switch router to help you get your switch router up and running. For more information about the Cisco IOS commands used in this chapter, refer to the Cisco IOS Command Reference publication. This chapter includes the following sections:
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Note You are at Step 3 in the suggested process for configuring your Layer 3 switch router (see Table 2-1). You should have already initially configured your switch router before proceeding with configuring interfaces. |
A switch router's main function is to relay packets from one data link to another. To do that, the characteristics of the interfaces through which the packets are received and sent must be defined. Interface characteristics include, but are not limited to, IP address, address of the port, data encapsulation method, and media type.
Many features are enabled on a per-interface basis. Interface configuration mode contains commands that modify the interface operation, for example, of an Ethernet port. When you issue the interface command, you must specify the interface type and number.
Layer 3 interfaces have both a Media Access Control (MAC) address and an interface port ID. The router keeps track of these designators and uses them to route traffic.
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Tips To find MAC addresses for a device, use the show interfaces command. |
The interface port ID designates the physical location of the Layer 3 interface within the switch router. This is the name that you use to identify the interface when configuring it. The system software uses interface port IDs to control activity within the switch router and to display status information. Interface port IDs are not used by other devices in the network; they are specific to the individual switch router and its internal components and software.
On the Catalyst 2948G-L3, the port IDs for the 48 Fast Ethernet interfaces are Fast Ethernet 1 through 48 and the port IDs for the 2 Gigabit Ethernet interfaces are Gigabit Ethernet 49 and 50. Similarly on the Catalyst 4908G-L3, the port IDs for the 8 Gigabit Ethernet interfaces are Gigabit Ethernet 1 through 8. You can use abbreviations such as f1 through f48 to configure the 48 Fast Ethernet interfaces and g49 or g50 to configure the 2 Gigabit Ethernet interfaces on the Catalyst 2948G-L3 switch router. On the Catalyst 4908G-L3 use gi1 as the abbreviation to configure Gigabit Ethernet interface 1 instead of g1.You can use Cisco IOS show commands to display information about a specific interface, or all the interfaces, in the switch router.
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Note If you use the abbreviated form of Gigabit Ethernet to configure the Gigabit Ethernet 1 interface on the Catalyst 4908G-L3, use gi1 as the port ID instead of g1. |
The following general configuration instructions apply to all interfaces. Before you configure interfaces, be sure to have the interface network (IP or IPX) addresses and the corresponding subnet mask information. If you do not have this information, consult your network administrator.
To configure an interface, follow these steps:
Router> enable Password: Router# configure terminal Router(config)#
Step 2 Enter the interface command, followed by the interface type (for example, Fast Ethernet or
Gigabit Ethernet) and its interface port ID (see the "Interface Port ID" section).
For example, to configure a Gigabit Ethernet port, use this command:
Router(config)# interface gigabitethernet number
Step 3 Follow each interface command with the interface configuration commands required for your particular interface.
The commands you enter define the protocols and applications that will run on the interface. The commands are collected and applied to the interface command until you enter another interface command, a command that is not an interface configuration command, or you enter end to return to privileged EXEC mode.
Step 4 Check the status of the configured interface by using the EXEC show commands.
Router# show interface gigabitethernet 49 Gigabit Ethernet49 is up, line protocol is up Hardware is xpif_port, address is 0050.3e7b.e907 (bia 0050.3e7b.e907) Internet address is 11.0.0.2/8 MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) Full-duplex, 1000Mb/s, GBIC connected, Force link-up ARP type:ARPA, ARP Timeout 04:00:00 Last input 03:27:17, output never, output hang never Last clearing of "show interface" counters never Queueing strategy:fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 945 packets input, 320796 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 watchdog, 927 multicast 0 input packets with dribble condition detected 943 packets output, 319527 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
Layer 3 switch routers support Fast Ethernet and Gigabit Ethernet interfaces. This section provides some examples of configurations for both interface types.
Use the following commands to configure an IP address on either a Fast Ethernet interface or a
Gigabit Ethernet interface starting in global configuration mode:
| Command | Purpose | |
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Step 1 | Router(config)# interface type number Router(config-if)# | Enters interface configuration mode to configure either the Gigabit Ethernet interface or the Fast Ethernet interface. |
Step 2 | Router(config-if)# | Enters the IP address and IP subnet mask to be assigned to the interface. |
Step 3 | Router(config-if)# | Enables the interface. |
Step 4 | Router(config-if)# exit Router(config)# | Returns to global configuration mode. Repeat Steps 1 to 3 to configure the other interfaces on the switch router. |
Step 5 | Router(config)# end Router# | Returns to privileged EXEC mode. |
Step 6 | Router# copy running-config startup-config | Saves configuration changes to NVRAM. |
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Tips Before you configure interfaces, be sure to have the interface network (IP or IPX) addresses and the corresponding subnet mask information. If you do not have this information, consult your network administrator. |
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Note The default setting for the negotiation mode is auto for the Fast Ethernet and Gigabit Ethernet interfaces. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router(config)# interface fastethernet number Router(config-if)# | Enters interface configuration mode to configure the Fast Ethernet interface. |
Step 2 | Router(config-if)# | Configures the transmission speed for 10 or 100 Mbps. If you set the speed for auto, you enable autonegotiation on the system—the switch router matches the speed and duplex mode of the partner node. |
Step 3 | Router(config-if)# | Configures for full or half duplex. |
Step 4 | Router(config-if)# no shutdown | Enables the interface. |
Step 5 | Router(config-if)# end Router# | Returns to privileged EXEC mode. |
Step 6 | Router# | Saves your configuration changes to NVRAM. |
The following example demonstrates initially configuring a Fast Ethernet interface with an IP address and autonegotiated speed and duplex:
Router(config)# interface fastethernet 1 Router(config-if)# ip address 10.1.2.4 255.0.0.0 Router(config-if)# speed auto Router(config-if)# duplex auto Router(config-if)# end Router# copy running-config startup-config
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Note The Catalyst 4908G-L3 switch router does not have Fast Ethernet interfaces. |
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Note The default setting for the negotiation mode is auto for the Gigabit Ethernet and Fast Ethernet interfaces. The Gigabit Ethernet port always operates at 1000 Mbps in full duplex mode. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router# Router#(config-if)# | Enters interface configuration mode to configure the Gigabit Ethernet interface. |
Step 2 | Router#(config-if)# | Sets negotiation mode to auto. The Gigabit Ethernet port attempts to negotiate the link with the partner port. The partner port should have the same configuration. When you set the Gigabit Ethernet interface to no negotiation auto, the port forces the link up no matter what the partner port setting is. |
Step 3 | Router#(config-if)# | Enables the interface. |
Step 4 | Router#(config-if) Router#(config)# | Returns to global configuration mode. Repeat Steps 1 to 3 to configure the other Gigabit Ethernet interfaces. |
Step 5 | Router#(config)# end Router# | Returns to privileged EXEC mode. |
Step 6 | Router# copy running-config startup-config | Saves configuration changes to NVRAM. |
The following example demonstrates initially configuring a Gigabit Ethernet interface with autonegotiation and an IP address:
Router(config)# interface gigabitethernet 49 Router(config-if)# negotiation auto Router(config-if)# ip address 10.1.2.3 255.0.0.0 Router(config-if)# end Router# copy running-config startup-config
The following output from the show interface command displays the Fast Ethernet interface's status and global parameters and includes port speed and duplex operation.
Router# show interface fastethernet 1 FastEthernet1 is up, line protocol is up Hardware is epif_port, address is 0030.40d6.4c07 (bia 0030.40d6.4c07) Internet address is 172.20.52.10/27 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) Auto-duplex, Auto Speed, 100BaseTX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output never, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 1 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 363371 packets input, 27266668 bytes, 0 no buffer Received 492 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 watchdog, 356363 multicast 0 input packets with dribble condition detected 9559 packets output, 4617122 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 0 interface resets 0 babbles, 0 late collision, 0 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
The following output from the show interface command displays the Gigabit Ethernet interface's status and global parameters and includes port speed and duplex operation.
Router# show interface gigabitethernet 1 GigabitEthernet1 is up, line protocol is up Hardware is xpif_port, address is 0030.40d6.4d07 (bia 0030.40d6.4d07) MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set, keepalive set (10 sec) Full-duplex, 1000Mb/s, 1000Base-SX, Auto-negotiation ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:17, output never, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/475, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 234 packets input, 81432 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort watchdog, 234 multicast 0 input packets with dribble condition detected 231 packets output, 79899 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 0 interface resets babbles, 0 late collision, 0 deferred lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
Posted: Thu Sep 7 09:18:14 PDT 2000
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