12-10
Catalyst 2975 Switch Software Configuration Guide
OL-19720-02
Chapter 12 Configuring Interface Characteristics
Understanding Interface Types
Connecting Interfaces
Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs
cannot exchange data without going through a routing device.
In the configuration shown in
, when Host A in VLAN 20 sends data to Host B in VLAN 30,
the data must go from Host A to the switch, to the router, back to the switch, and then to Host B.
Figure 12-1
Connecting VLANs with Layer 2 Switches
With a standard Layer 2 switch, ports in different VLANs have to exchange information through a
router. By using the switch with routing enabled, when you configure both VLAN 20 and VLAN 30 with
an SVI to which an IP address is assigned, packets can be sent from Host A to Host B directly through
the switch with no need for an external router (
).
Figure 12-2
Connecting VLANs with a Layer 3 Switch
Host A
Switch
Cisco router
VLAN 20
Host B
VLAN 30
46647
Host A
SVI 1
172.20.128.1
172.20.129.1
SVI 2
Layer 3 switch
with routing enabled
VLAN 20
Host B
VLAN 30
101350