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Table of Contents

Configuring Interfaces

Configuring Interfaces

This chapter describes basic interface configuration for the Server Load Balancing (SLB) switch to help you get your SLB switch up and running. Also included are sections about virtual LANs (VLANs).

For further information about the commands used in this chapter, refer to the command reference publications in the Cisco IOS documentation set and to "Command Reference."

This chapter includes the following sections:


Note   You are at Step 5 in the suggested process for configuring your SLB switch. See the "Configuring Your SLB Switch" section. By now you have set up the hardware and are ready to proceed with configuring interfaces.

Overview of Interface Configuration

The main function of a SLB switch is to relay packets from one data link to another. To do that, you must define the characteristics of the interfaces through which the packets are received and sent. 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. When you issue the interface command, you must define the interface type and number.

The following general guidelines apply to IP physical and virtual interface configuration processes.

  A subinterface is a mechanism that allows a single physical interface to support multiple logical interfaces or networks—that is, several logical interfaces or networks can be associated with a single hardware interface. Configuring multiple virtual interfaces, or subinterfaces, on a single physical interface allows greater flexibility and connectivity on the network.

About Interface Addresses and Names

Layer 3 interfaces have both a Media Access Control (MAC) address and an interface port ID. The SLB switch keeps track of these designators and uses them to route traffic.

Media Access Control Address

The MAC address, also referred to as the hardware address, is required for every port or device that connects to a network. Other devices in the network use MAC addresses to locate specific ports in the network and to create and update routing tables and data structures.


Tips To find the MAC address for a device, use the show interfaces command.

Interface Port ID

The interface port ID designates the physical number of the SLB or Layer 3 interface. 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 SLB switch and to display status information. Interface port IDs are not used by other devices in the network; they are specific to the individual SLB switch and its internal components and software.

The Fast Ethernet interface ports are numbered from 1 through 40 and the two Gigabit Ethernet interface ports are numbered 41and 42. For example, the first Fast Ethernet interface ID is Fastethernet1 and the first gigabit Ethernet interface ID is GigabitEthernet41.

You can identify module ports by physically checking the port number on the back of the SLB switch. You can also use Cisco IOS show commands to display information about a specific interface, or all the interfaces, in the SLB switch.

General Instructions for Configuring Interfaces

The following general configuration instructions apply to all interfaces. Begin in global configuration mode. To configure an interface, follow these steps:


Step 1   Use the configure EXEC command at the privileged EXEC prompt to enter the global configuration mode.

SLB-Switch> enable

SLB-Switch# configure terminal

SLB-Switch(config)#
 

Step 2   From global configuration mode, 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 the Gigabit Ethernet port 41, use this command:

SLB-Switch(config)# interface gigabitethernet 41

 

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   Once an interface is configured, you can check its status by using the EXEC show commands.

SLB-Switch# show interfaces gigabitEthernet 41

GigabitEthernet41 is administratively down, line protocol is down
  Hardware is xpif_port, address is 0050.3e7e.f107 (bia 0050.3e7e.f107)
  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 never, 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
     0 packets input, 0 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, 0 multicast
     0 input packets with dribble condition detected
     0 packets output, 0 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
SLB-Switch#

About Layer 3 Switching Interfaces

The Catalyst 4840G SLB switch supports 40 Fast Ethernet and 2 Gigabit Ethernet interfaces. This section provides some examples of configurations for both interface types.

Initially Configuring Gigabit Ethernet Interfaces

The following steps show how to configure an IP address and autonegotiation on a Gigabit Ethernet interface starting in global configuration mode:

Command Purpose

Step 1 

SLB-Switch(config)# interface 
gigabitethernet interface_number

SLB-Switch(config-if)#

Enters Ethernet interface configuration mode to configure the Gigabit Ethernet interface.

Step 2 

SLB-Switch(config-if)# [no] negotiation 
auto

Specifies the negotiation mode.

When you set negotiation mode to auto, the Gigabit Ethernet port attempts to negotiate the link (the duplex setting) with the partner port.

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. This brings up the link with 1000 Mbps and full duplex only.

Step 3 

SLB-Switch(config-if)# ip address 
ip-address subnet-mask

Specifies the IP address and IP subnet mask to be assigned to the Gigabit Ethernet interface.

Step 4 

SLB-Switch(config-if)# exit

SLB-Switch(config)#

Returns to global configuration mode. Repeat Steps 1 to 3 to configure the second Gigabit Ethernet interface.

Step 5 

SLB-Switch(config)# end

Returns to privileged EXEC mode.

Step 6 

SLB-Switch# copy system:running-config 
nvram:startup-config

Saves your configuration changes to NVRAM.

The following example demonstrates initially configuring a Gigabit Ethernet interface with autonegotiation and an IP address:

SLB-Switch(config)# interface gigabitethernet 41

SLB-Switch(config-if)# negotiation auto

SLB-Switch(config-if)# ip address 10.1.2.3 255.0.0.0

SLB-Switch(config-if)# exit

SLB-Switch(config)# end

SLB-Switch# copy system:running-config nvram:startup-config

Initially Configuring Fast Ethernet Interfaces

Use the following procedure to assign an IP address to the Fast Ethernet 10Base-T or 100Base-T interface of your SLB switch so that it can be recognized as a device on the Ethernet LAN. The Fast Ethernet interface supports 10-Mbps and 100-Mbps speeds with Cisco 10Base-T and 100Base-T routers, hubs, switches, and SLB switches.

Command Purpose

Step 1 

SLB-Switch(config)# interface fastethernet 
interface_number

SLB-Switch(config-if)#

Enters Ethernet interface configuration mode to configure the Fast Ethernet interfaces.

Step 2 

SLB-Switch(config-if)# ip address 
ip-address subnet-mask

Specifies the IP address and IP subnet mask to be assigned to the Fast Ethernet interface.

Step 3 

SLB-Switch(config-if)# [no] speed [10 | 100 
| auto]

Configures the transmission speed for 10 or 100 Mbps, or for autonegotiation (the default). If you set the speed to auto, you enable autonegotiation, and the SLB switch matches the speed of the partner node.

Step 4 

SLB-Switch(config-if)# [no] duplex [full | 
half | auto]

Configures for full or half duplex. If you set duplex for auto, the SLB switch matches the duplex setting of the partner node.

Step 5 

SLB-Switch(config-if)# end

SLB-Switch#

Returns to privileged EXEC mode.

Step 6 

SLB-Switch# copy system:running-config 
nvram:startup-config

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:

SLB-Switch(config)# interface fastethernet 1

SLB-Switch(config-if)# ip address 10.1.2.4 255.0.0.0

SLB-Switch(config-if)# speed auto

SLB-Switch(config-if)# duplex auto

SLB-Switch(config-if)# end

SLB-Switch# copy system:running-config nvram:startup-config

Monitoring the Ethernet Interfaces

To verify the settings after you have configured Gigabit Ethernet or Ethernet 10/100 Base-T operation, use the following commands:

Command
Purpose
show interface gigabitethernet 
interface_number

Displays the status and global parameters of the Gigabit Ethernet interface.

show interface fastethernet 
interface_number

Displays the status and global parameters of the Fast Ethernet interface.

The following example shows sample output from the show interfaces gigabitethernet command:

SLB-Switch# show interfaces gigabitethernet 41

GigabitEthernet41 is down, line protocol is down
  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 1d19h, 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
     4217 packets input, 1475664 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, 4217 multicast
     0 input packets with dribble condition detected
     4397 packets output, 1465255 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
SLB-Switch#
 

The following example shows sample output from the show interface fastethernet command:

SLB-Switch# show interfaces fastEthernet 1

FastEthernet1 is up, line protocol is up
  Hardware is epif_port, address is 0050.3e7e.f007 (bia 0050.3e7e.f007)
  Internet address is 172.20.52.9/27
  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 1000 bits/sec, 2 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     1200042 packets input, 90451466 bytes, 0 no buffer
     Received 21167 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     0 watchdog, 1177312 multicast
     0 input packets with dribble condition detected
     10938 packets output, 3651546 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
SLB-Switch#

About Virtual LANs

Virtual LANs enable network managers to group users logically rather than by physical location. A virtual LAN (VLAN) is an emulation of a standard LAN that allows data transfer and communication to occur without the traditional restraints placed on the network. It can also be considered a broadcast domain set up within a switch. With VLANs, switches can support more than one subnet (or VLAN) on each switch, and give routers and switches the opportunity to support multiple subnets on a single physical link. A group of devices on a LAN are configured so that they communicate as if they were attached to the same LAN segment, when they are actually located on different segments. Layer 3 switching supports up to 255 VLANs per system.

VLANs enable efficient traffic separation and provide excellent bandwidth utilization. VLANs also alleviate scaling issues by logically segmenting the physical LAN structure into different subnetworks so that packets are switched only between ports within the same VLAN. This can be very useful for security, broadcast containment, and accounting.

Layer 3 switching software supports a port-based VLAN on a trunk port, which is a port that carries the traffic of multiple VLANs. Each frame transmitted on a trunk link is tagged as belonging to only one VLAN.

Layer 3 switching software supports VLAN frame encapsulation through the Inter-Switch Link (ISL) protocol and the 802.1Q standard.

Figure 6-1 shows a network topology where two VLANs span a Catalyst 5500 switch and Catalyst 4840G SLB switch.

Both VLANs in this topology are bridged using the Inter-Switch Link (ISL) protocol.


Figure 6-1: VLAN Spanning Devices in a Network



Note   The four adjacent ports (such as one through four, or five through eight) on the 10/100 interfaces must all use the same VLAN encapsulation; that is, either 802.1Q and native, or ISL and native.

Configuring ISL VLAN Encapsulation

ISL is a Cisco protocol for interconnecting multiple switches and maintaining VLAN information as traffic travels between switches.

The VLAN configuration example shown in Figure 6-2 depicts the following:


Figure 6-2: Example of an ISL VLAN Bridging Configuration


To configure the Layer 3 VLANs shown in Figure 6-2, perform the following steps:

Command Purpose

Step 1 

SLB-Switch(config)# interface fastethernet 
interface_number.subinterface

SLB-Switch(config-subif)#

Enters subinterface configuration mode.

Step 2 

SLB-Switch(config-subif)# encapsulation isl 
vlan-id

Specifies ISL encapsulation for the Ethernet frames sent from this subinterface with a header that maintains the specified VLAN ID between network nodes.

Step 3 

SLB-Switch(config-subif)# bridge-group 
bridge-group

Assigns the subinterface a bridge group number.


Note   When you are configuring VLAN routing, skip this step.

Step 4 

SLB-Switch(config-subif)# interface 
fastethernet interface_number

SLB-Switch(config-if)#

Enters interface configuration mode to configure the Fast Ethernet main interface.

Step 5 

SLB-Switch(config-if)# bridge-group 
bridge-group

Assigns the main interface to the bridge group.

Step 6 

SLB-Switch(config-if)# exit

SLB-Switch(config)#

Returns to global configuration mode.

Step 7 

SLB-Switch(config)# bridge bridge-group 
protocol ieee

Specifies that the bridge group will use the IEEE Ethernet Spanning-Tree Protocol.

The following example shows how to configure the interfaces for VLAN bridging with ISL encapsulation shown in Figure 6-2:

SLB-Switch(config)# interface fastethernet 1.1

SLB-Switch(config-subif)# encap isl 50

SLB-Switch(config-subif)# bridge-group 1

SLB-Switch(config-subif)# interface fastethernet 0

SLB-Switch(config-if)# bridge-group 1

SLB-Switch(config-if)# exit

SLB-Switch(config)# bridge 1 protocol ieee

SLB-Switch(config)# interface fastethernet 1.2

SLB-Switch(config-subif)# encap isl 100

SLB-Switch(config-subif)# bridge-group 2

SLB-Switch(config-subif)# interface fastethernet 3

SLB-Switch(config-subif)# bridge-group 2

SLB-Switch(config-subif)# exit

SLB-Switch(config)# bridge 2 protocol ieee

SLB-Switch(config)# exit

SLB-Switch# copy system:running-config nvram:startup-config

 

When configuring ISL with IP, you cannot configure IP addresses on a subinterface unless the VLANs are already configured (that is, you must have already entered the encapsulation isl or encapsulation dot1q command).

The maximum VLAN bridge group values are as follows:

For a complete configuration example for VLANs with ISL encapsulation, see the "Example of an SLB and Layer 3 Switch with ISL, VLAN, and BVI with GEC" section.

To monitor the VLANs once they are configured, use the commands described in the "Monitoring VLAN Operation" section.

Configuring 802.1Q VLAN Encapsulation

The IEEE 802.1Q standard provides a method for secure bridging of data across a shared backbone. IEEE 802.1Q VLAN encapsulation uses an internal, or one level, packet tagging scheme to multiplex VLANs across a single physical link, while maintaining strict adherence to the individual VLAN domains.

On an IEEE 802.1Q trunk port, all transmitted and received frames are tagged except for those on the one VLAN configured as the PVID (port VLAN identifier) or native VLAN for the port. Frames on the native VLAN are always transmitted untagged and are normally received untagged.

The VLAN configuration example shown in Figure 6-3 depicts the following:


Figure 6-3: Example of Bridging Between Native and Non-Native 802.1Q VLANs


To configure the bridging between native VLAN 1 and non-native VLAN 100 depicted in Figure 6-3, perform the following steps:

Command Purpose

Step 1 

SLB-Switch(config)# interface fastethernet 
interface_number.subinterface

Enters subinterface configuration mode.

Step 2 

SLB-Switch(config-subif)# encap dot1q 
vlan-id native

Specifies 802.1Q encapsulation for Ethernet frames sent from the subinterface with a header that maintains the specified native VLAN ID between network nodes.

Step 3 

SLB-Switch(config-subif)# bridge-group 
bridge-group

Assigns the subinterface a bridge group number.


Note   When you are configuring VLAN routing, skip this step.

Step 4 

SLB-Switch(config-subif)# interface 
fastethernet interface_number

Enters interface configuration mode to configure the Fast Ethernet main interface.

Step 5 

SLB-Switch(config-if)# bridge-group 
bridge-group

Assigns the main interface to the bridge group.

Step 6 

SLB-Switch(config-if)# exit

Returns to global configuration mode.

Step 7 

SLB-Switch(config)# bridge bridge-group 
protocol ieee

Specifies that the bridge group will use the IEEE Ethernet Spanning-Tree Protocol.

The following example shows how to configure the bridging between native and non-native 802.1Q VLANS shown in Figure 6-3:

SLB-Switch(config)# interface fastethernet 2.1

SLB-Switch(config-subif)# encap dot1q 1 native

SLB-Switch(config-subif)# bridge-group 1

SLB-Switch(config-subif)# interface fastethernet 1

SLB-Switch(config-if)# bridge-group 1

SLB-Switch(config-if)# exit

SLB-Switch(config)# bridge 1 protocol ieee

SLB-Switch(config)# interface fastethernet 2.2

SLB-Switch(config-subif)# encap dot1q 100

SLB-Switch(config-subif)# bridge-group 2

SLB-Switch(config-subif)# interface fastethernet 3

SLB-Switch(config-subif)# bridge-group 2

SLB-Switch(config-subif)# exit

SLB-Switch(config)# bridge 2 protocol ieee

SLB-Switch(config)# exit

SLB-Switch# copy system:running-config nvram:startup-config

Monitoring VLAN Operation

Once the VLANs are configured on the SLB switch, you can monitor their operation using the following commands:

Command
Purpose
show vlan vlan-id

Displays information on all configured VLANs or on a specific VLAN (by VLAN ID number).

clear vlan 
vlan-id

Clears the counters for all VLANs, when the VLAN ID is not specified.

debug vlan packet

Displays contents of the packets sent to and exiting from the route processor.

To configure encapsulation over the EtherChannel, see the "About Encapsulation over EtherChannel" section.

Example of an SLB and Layer 3 Switch with ISL, VLAN, and BVI with GEC

This example configuration focuses on both the Inter-Switch Link (ISL) and virtual LANs (VLANs), as well as integrated routing and bridging (IRB) using a bridge-group virtual interface (BVI) over Gigabit EtherChannel (GEC). The Cisco proprietary ISL allows any Fast Ethernet port to be configured as a trunk. The Spanning-Tree Protocol detects and breaks loops on all the VLANs carried across the trunk.

!
ip subnet-zero
no ip domain-lookup
ip name-server 171.69.2.132
ip name-server 198.92.30.32
bridge irb
!
interface FastEthernet1
    no ip address no ip directed-broadcast no keepalive
!
interface FastEthernet1.128
    ip address 172.68.16.10 255.255.255.0 ip helper-address 172.68.16.15 no ip redirects no ip directed-broadcast encapsulation isl 128
!
interface FastEthernet1.199
    ip address 172.68.17.15 255.255.255.0 ip helper-address 172.68.16.16 ip helper-address 172.68.16.17 ip helper-address 172.68.16.18 no ip redirects no ip directed-broadcast encapsulation isl 199
!
interface FastEthernet1.201
    ip address 172.68.18.10 255.255.255.0 ip helper-address 172.68.16.16 ip helper-address 172.68.16.17 ip helper-address 172.68.16.18 no ip redirects no ip directed-broadcast encapsulation isl 201
!
interface FastEthernet2
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet3
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet4
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet5
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet6
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet7
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet8
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet9
    ip address 172.68.19.10 255.255.255.0 ip helper-address 172.68.16.16 ip helper-address 172.68.16.17 ip helper-address 172.68.16.18 no ip redirects no ip directed-broadcast ip sdr listen no keepalive
!
interface FastEthernet10
    no ip address no ip directed-broadcast no keepalive shutdown
!
interface FastEthernet11
    no ip address no ip directed-broadcast no keepalive shutdown
!
.
(Information Deleted)
.
interface GigabitEthernet41
!
interface GigabitEthernet42
 ip address 172.68.1.1 255.255.255.0
 no ip directed-broadcast
!
interface BVI1
 ip address 171.201.1.2 255.255.255.0
 no ip directed-broadcast
 no ip route-cache cef
!
router eigrp 170
 network 171.200.0.0
 network 171.201.0.0
 network 172.68.0.0
 network 172.69.0.0
 no auto-summary
!
router bgp 180
 network 172.68.1.0
 network 172.69.1.0
 no auto-summary
!
ip classless
!
bridge 1 protocol ieee
bridge 1 route ip
!
ip http server
!
line con 0
line aux 0
line vty 0 4
    login
!
ntp clock-period 17181168
ntp update-calendar
ntp server 171.71.150.52
ntp server 171.69.4.143
ntp server 171.69.5.10
end


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Posted: Thu Sep 28 15:24:35 PDT 2000
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