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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:
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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. |
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.
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.
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Tips To find the MAC address for a device, use the show interfaces command. |
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.
The following general configuration instructions apply to all interfaces. Begin in global configuration mode. To configure an interface, follow these steps:
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#
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.
| 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
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 | 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
Displays the status and global parameters of the Gigabit Ethernet interface. Displays the status and global parameters of the Fast Ethernet interface.
Command
Purpose
show interface gigabitethernet
interface_number
show interface fastethernet
interface_number
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#
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.

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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. |
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:

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)# | |||
Step 2 | SLB-Switch(config-subif)# encapsulation isl vlan-id | |||
Step 3 | SLB-Switch(config-subif)# bridge-group bridge-group | Assigns the subinterface a bridge group number.
| ||
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 1.1SLB-Switch(config-subif)#encap isl 50SLB-Switch(config-subif)#bridge-group 1SLB-Switch(config-subif)#interface fastethernet 0SLB-Switch(config-if)#bridge-group 1SLB-Switch(config-if)#exitSLB-Switch(config)#bridge 1 protocol ieeeSLB-Switch(config)#interface fastethernet 1.2SLB-Switch(config-subif)#encap isl 100SLB-Switch(config-subif)#bridge-group 2SLB-Switch(config-subif)#interface fastethernet 3SLB-Switch(config-subif)#bridge-group 2SLB-Switch(config-subif)#exitSLB-Switch(config)#bridge 2 protocol ieeeSLB-Switch(config)#exitSLB-Switch#copy system:running-config nvram:startup-config
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.
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:

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 | |||
Step 2 | SLB-Switch(config-subif)# encap dot1q vlan-id native | |||
Step 3 | SLB-Switch(config-subif)# bridge-group bridge-group | Assigns the subinterface a bridge group number.
| ||
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 2.1SLB-Switch(config-subif)#encap dot1q 1 nativeSLB-Switch(config-subif)#bridge-group 1SLB-Switch(config-subif)#interface fastethernet 1SLB-Switch(config-if)#bridge-group 1SLB-Switch(config-if)#exitSLB-Switch(config)#bridge 1 protocol ieeeSLB-Switch(config)#interface fastethernet 2.2SLB-Switch(config-subif)#encap dot1q 100SLB-Switch(config-subif)#bridge-group 2SLB-Switch(config-subif)#interface fastethernet 3SLB-Switch(config-subif)#bridge-group 2SLB-Switch(config-subif)#exitSLB-Switch(config)#bridge 2 protocol ieeeSLB-Switch(config)#exitSLB-Switch#copy system:running-config nvram:startup-config
Command | Purpose |
|---|---|
show vlan vlan-id |
|
clear vlan vlan-id |
|
debug vlan packet |
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To configure encapsulation over the EtherChannel, see the "About Encapsulation over EtherChannel" section.
! ip subnet-zero no ip domain-lookup ip name-server 171.69.2.132 ip name-server 198.92.30.32 bridge irb ! interface FastEthernet1no ip address no ip directed-broadcast no keepalive
! interface FastEthernet1.128ip 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 FastEthernet1.199ip 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 FastEthernet1.201ip 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 FastEthernet2no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet3no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet4no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet5no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet6no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet7no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet8no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet9ip 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 FastEthernet10no ip address no ip directed-broadcast no keepalive shutdown
! interface FastEthernet11no 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 4login
! 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
Copyright 1989-2000©Cisco Systems Inc.