Configuration Examples

This chapter provides real-world examples of Layer 3 switching configurations.

Note The IP, IPX, and network addresses in these examples are generic addresses, so you must replace them with the actual addresses for your network.

Example of a Catalyst 2948G-L3 with ISL and VLAN

This example configuration for a Catalyst 2948G-L3 focuses on Inter-Switch Link (ISL) and virtual LANs (VLANs), integrated routing and bridging (IRB) using a bridge group virtual interface (BVI), Fast EtherChannel (FEC), and Gigabit Etherchannel (GEC). The Cisco proprietary ISL allows any Fast Ethernet port to be configured as a trunk. This example also includes multicast routing.

version 12.0
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname cat2948G-L3
!
no logging console
enable secret 5 $1$1$1$1$1$1$1$1$1$
enable password changme
!
sdm size ipx-bvi-network 256 
sdm size ip-adjacency 1056 
sdm size ipx-node 1024 
sdm size ip-prefix 8000 
sdm size ipx-network 2048 
sdm size ip-mcast 2000 
sdm size udp-flooding 512 
sdm size l2-switching 5000 
sdm autolearn
ip subnet-zero
no ip domain-lookup
ip multicast-routing
ipx routing 0050.3e7b.c800
bridge irb
!
!
!
interface Port-channel1
 ip address 1.200.0.1 255.255.0.0
 no ip redirects
 no ip unreachables
 no ip directed-broadcast
 ipx network 1200 encapsulation ARPA
 hold-queue 300 in
!
interface FastEthernet1
 no ip address
 no ip directed-broadcast
!
interface FastEthernet1.100
 encapsulation isl 100
 ip address 1.1.0.1 255.255.0.0
 no ip redirects
 no ip directed-broadcast
 ip pim dense-mode
 ipx network 1001 encapsulation ARPA
!
interface FastEthernet2
 no ip address
 no ip redirects
 no ip directed-broadcast
!
interface FastEthernet2.200
 encapsulation isl 200
 ip address 1.2.0.1 255.255.0.0
 no ip redirects
 no ip directed-broadcast
 ip pim dense-mode
 ipx network 1002 encapsulation ARPA
!
interface FastEthernet3
 no ip address
 no ip directed-broadcast
!
interface FastEthernet4
 no ip address
 no ip directed-broadcast
 bridge-group 10
!
interface FastEthernet5
 no ip address
 no ip redirects
 no ip unreachables
 no ip directed-broadcast
 bridge-group 10
!
interface FastEthernet6
 no ip address
 no ip directed-broadcast
 bridge-group 10
!
interface FastEthernet7
 no ip address
 no ip directed-broadcast
 bridge-group 10
!
interface FastEthernet8
 no ip address
 no ip directed-broadcast
 shutdown
!
<information deleted>

interface FastEthernet47
 no ip address
 no ip directed-broadcast
 shutdown
!
interface FastEthernet48
 ip address 24.0.4.4 255.0.0.0
 no ip directed-broadcast
 shutdown
 duplex full
 speed 10
!
interface GigabitEthernet49
 no ip address
 no ip directed-broadcast
 channel-group 1
!
interface GigabitEthernet50
 no ip address
 no ip directed-broadcast
 channel-group 1
!
interface BVI10
 ip address 1.3.0.1 255.255.0.0
 no ip directed-broadcast
 no ip route-cache cef
 ipx network 1003 encapsulation ARPA
!
router eigrp 100
 network 1.0.0.0
!
ip classless
!
!
bridge 10 protocol ieee
 bridge 10 route ip
 bridge 10 route ipx
!
line con 0
 exec-timeout 0 0
 transport input none
line aux 0
line vty 0 4
 password changme
 login
!
 
end

Example of a Catalyst 2948G-L3 with HSRP

This example configuration for a Catalyst 2948G-L3 switch router focuses on the Hot Standby Router Protocol (HSRP), which provides high network availability. HSRP makes network topology changes transparent to the host. The active router is monitored by other standby routers, and as soon as an active router becomes unavailable, the standby router takes its place.

Helper addresses facilitate connectivity by forwarding certain broadcasts to a target server. In this example, an IP Helper address identifies the Dynamic Host Configuration Protocol (DHCP) server IP address. This configuration also includes configuration for IP multicast, Distance Vector Multicast Routing Protocol (DVMRP), tunneling, and Protocol Independent Multicast (PIM) in sparse mode.

version 12.0
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname cat2948g-2
!
no logging console
enable secret 5 $1$1$1$1$1$1$1$1$1$1$1$
enable password changeme
!
sdm size ipx-bvi-network 256 
sdm size ip-adjacency 1056 
sdm size ipx-node 1024 
sdm size ip-prefix 8000 
sdm size ipx-network 2048 
sdm size ip-mcast 2000 
sdm size udp-flooding 512 
sdm size l2-switching 5000 
sdm autolearn
ip subnet-zero
no ip domain-lookup
ipx routing 0050.3e7b.c800
!
!
!
interface FastEthernet1
ip address 172.69.95.197 255.255.255.192
no ip directed-broadcast
!
interface FastEthernet1
description Bldg 1 Network A
ip address 172.69.93.1 255.255.255.192
ip helper-address 172.69.2.74
ip helper-address 172.69.2.123
ip helper-address 172.69.30.31
ip helper-address 172.69.2.121
ip helper-address 172.71.84.140
ip helper-address 172.69.67.35
no ip redirects
no ip directed-broadcast
ip pim sparse-mode
standby priority 200
standby preempt
standby ip 172.69.93.6
!
interface FastEthernet2
ip address 172.69.90.1 255.255.255.0
 ip helper-address 172.69.2.74
 ip helper-address 172.69.2.123
 ip helper-address 172.69.30.31
 ip helper-address 172.69.2.121
 ip helper-address 172.71.84.140
 ip helper-address 172.69.67.35
 no ip redirects
 no ip directed-broadcast
 ip pim sparse-mode
 standby priority 200
 standby preempt
 standby ip 172.69.90.6
!
interface FastEthernet3
ip address 172.69.91.1 255.255.255.0
ip helper-address 172.69.2.74
ip helper-address 172.69.2.123
ip helper-address 172.69.30.31
ip helper-address 172.69.2.121
ip helper-address 172.71.84.140
ip helper-address 172.69.67.35
no ip redirects
no ip directed-broadcast
ip pim sparse-mode
standby priority 200
standby preempt
standby ip 172.69.91.6
!
interface FastEthernet4
description Building 2 Network A
ip address 172.69.88.1 255.255.255.192
ip helper-address 172.69.2.74
ip helper-address 172.69.2.123
ip helper-address 172.69.30.31
ip helper-address 172.69.2.121
ip helper-address 172.71.84.140
ip helper-address 172.69.67.35
no ip redirects
no ip directed-broadcast
ip pim sparse-mode
standby priority 200
standby preempt
standby ip 172.69.88.6
!
interface FastEthernet5
description Building 3 Network A
ip address 172.69.89.1 255.255.255.192
ip helper-address 172.69.2.74
ip helper-address 172.69.2.123
ip helper-address 172.69.30.31
ip helper-address 172.69.2.121
ip helper-address 172.71.84.140
ip helper-address 172.69.67.35
no ip redirects
no ip directed-broadcast
ip pim sparse-mode
standby priority 200
standby preempt
standby ip 172.69.89.6
!
interface FastEthernet6
no ip address
no ip directed-broadcast
!
<information deleted>
 
 
interface FastEthernet47
 no ip address
 no ip directed-broadcast
 shutdown
!
interface FastEthernet48
 ip address 24.0.4.4 255.0.0.0
 no ip directed-broadcast
 shutdown
 duplex full
 speed 10
!
interface GigabitEthernet49
 no ip address
 no ip directed-broadcast
 shutdown
!
interface GigabitEthernet50
 no ip address
 no ip directed-broadcast
 shutdown
!
!
router eigrp 109
network 172.69.0.0
no auto-summary
!
 
ip pim accept-rp auto-rp
ip pim accept-rp 172.69.10.13
logging 172.69.43.19
snmp-server community 8540 RO 98
snmp-server community Cisco RW 99
snmp-server host 172.69.43.19 traps public
tacacs-server host 172.69.2.210
tacacs-server host 172.69.35.87
tacacs-server timeout 15
!
line con 0
password 7 071B245F5A
transport input none
line aux 0
password 7 071B245F5A
line vty 0
exec-timeout 0 0
login authentication admin
line vty 1
exec-timeout 0 0
login authentication admin
length 57
line vty 2 4
exec-timeout 0 0
login authentication admin
!
 
end

Example of a Catalyst 2948G-L3 with Bridging

This example configuration for the Catalyst 2948G-L3 shows the 48 Fast Ethernet and 2 Gigabit Ethernet ports as part of one bridge group.

version 12.0
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname cat2948G-L3
!
no logging console
enable secret 5 $1$1$1$1$1$1$1$1$1$
enable password changme
!
sdm size ipx-bvi-network 256 
sdm size ip-adjacency 1056 
sdm size ipx-node 1024 
sdm size ip-prefix 8000 
sdm size ipx-network 2048 
sdm size ip-mcast 2000 
sdm size udp-flooding 512 
sdm size l2-switching 5000 
sdm autolearn
!
!
interface FastEthernet1
 no ip address
 no ip directed-broadcast
 bridge-group 1
!
interface FastEthernet2
 no ip address
 no ip directed-broadcast
 bridge-group 1
!
interface FastEthernet3
 no ip address
 no ip directed-broadcast
 bridge-group 1
!
<information deleted>

interface GigabitEthernet49
 no ip address
 no ip directed-broadcast
 bridge-group 1
!
interface GigabitEthernet50
 no ip address
 no ip directed-broadcast
 bridge-group 1
!
no ip routing
 
bridge 1 protocol ieee
 
!
 
line con 0
 exec-timeout 0 0
 transport input none
line aux 0
line vty 0 4
 password changme
 login
!
end

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