Cisco Catalyst WS-X3001 Installation And Configuration Manual page 29

VLAN Trunks
A trunk is a physical link between two Catalyst switches, or between Catalyst switches and routers,
that carries the traffic of multiple VLANs. Trunks allow you to extend VLANs from one Catalyst
switch to another. Users usually connect switches to each other and to routers using high-speed
interfaces, such as Fast Ethernet, FDDI, and ATM.
The Catalyst series switch provides a means of multiplexing VLANs between switches and routers
by using ISL on Fast Ethernet or LAN emulation on ATM protocols:
You can use any combination of these trunk technologies to form enterprise-wide VLANs. You can
choose between low-cost copper and long-distance fiber connections for your trunks. An ISL trunk
is like a continuation of the switching backbone. It provides a means for the Catalyst to multiplex
VLANs between switches and routers.
Figure 20 and Figure 21 are examples of a Fast Ethernet ISL configuration.
Figure 20
Customer Support
Figure 21
Fast Ethernet ISL Configuration Example
VLAN 1
Catalyst
Engineering
VLAN 2
Manufacturing
VLAN 3
Switched VLAN
Fast Ethernet ISL Configuration Example
Trunk Trunk
Catalyst
switch
Catalyst
switch
VLAN1 VLAN3
VLAN2
Catalyst Matrix and Expansion Module Installation and Configuration Guide
Catalyst
1200 1200
FDDI
Enterprise FDDI
Catalyst
switch
Trunk Trunk
Catalyst
Catalyst
switch
VLAN2
VLAN1
ISL Functional Overview and Specifications
Customer Support
VLAN 1
Engineering
VLAN
2
VLAN 2
Manufacturing
VLAN 3
Switched VLAN
switch
VLAN3
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