VLAN 1 is not used for management. All ports in Catalyst switches default to VLAN 1, and any
devices connected to non−configured ports will be in VLAN 1. This may cause potential issues for
the management of switches, as explained above.
•
A Layer 3 (L3) (routed) port is used to connect to the default gateway port. In this diagram, a Cisco
7200VXR router could be easily replaced by a firewall that connects to the Internet gateway router.
•
A routing protocol is not run between the stack of Catalyst 3750s and the Internet gateway router.
Instead, a static default route is configured on the 3750. This setup is preferred if there is only one
route to the Internet. Make sure to configure static routes (preferably summarized) on the gateway
router (7200VXR) for subnets that can be reached by the Catalyst 3750s. This step is very important
since routing protocols are not being used.
•
If you need additional bandwidth for the uplink ports, you can configure EtherChannel. Configuring
EtherChannel also provides link redundancy in case of a link failure.
•
Configurations
This document uses the configurations shown below.
Catalyst 3750• Catalyst 2950• Catalyst 2948G•
As you can see below, although there are two Catalyst 3750 switches stacked together, they are configured
just as if they had only one switch. Both switches have twenty−four 10/100/1000 interfaces and in the
configuration they show up as gigabit Ethernet 1/0/1 up to gigabit 1/0/24 for the first switch, and gigabit 2/0/1
up to gigabit 2/0/24 for the second one. So looking at the configuration, it appears as if there is just one switch
with two modules that each have 24 ports.
Extending this exercise to 3, 4, 5, and so on, switches in a stack would appear similar, but for each switch that
is added to the stack, it shows up in the configuration as if one module is added to the switch.
Cat3750 (Cisco Catalyst 3750G−24T)
C3750G−24T#show run
Building configuration...
Current configuration : 2744 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password−encryption
!
hostname C3750G−24T
!
!
ip subnet−zero
ip routing
!
no ip domain−lookup
!
spanning−tree mode pvst
no spanning−tree optimize bpdu transmission
spanning−tree extend system−id
!
!
!
interface GigabitEthernet1/0/1
Cisco − Configuring Inter−VLAN Routing with Catalyst 3750 Series Switches in a Stacked Configuration