Cisco 3200 Series Hardware Reference Manual page 128

Inter-VLAN Routing
Figure C-3
Dest
Dest
Token-Ring Encapsulation Flag
Inter-VLAN Routing
In a VLAN network, traffic and stations for multiple network layer subnets (VLANs) can coexist on a
single physical LAN segment. In practice, a single VLAN corresponds to a network subnet, and a VLAN
trunking capable router is required to forward traffic from a first VLAN to a second VLAN for a Layer 2
switch.
The FESMIC enables the Cisco 3200 Series router to become one of first IOS Ethernet switching routers
to deliver intelligent Layer 2 switching capability and Layer 3 inter-VLAN routing in a single box
solution, as shown in
Figure C-4
Floor 3
Floor 2
Floor 1
Cisco 3200 Series Router Hardware Reference
C-4
802.1Q Tag Format in an Ethernet Frame
Src Len/Etype Data
Src Etype Tag Len/Etype
VLAN-ID
Etype
Figure C-4
Switching Router Network Topology
Traditional Switch and Router Topology.
VLAN1 VLAN2 VLAN3
L2 Switch
L2 Switch
Router
L2 Switch
Original
FCS
Frame
Tagged
Data FCS
Frame
VLAN-ID and
TR encapsulation are
802.IQ, not 802.IP.
Switching Router Topology.
VLAN1
Switching
Router
Switching
Router
Switching
Router
Appendix C Switch Port Functionality
VLAN2 VLAN3
Floor 3
Floor 2
Floor 1
OL-5816-10