Multilayer Switching - Router Alley

Multilayer Switching vs. Router on a Stick
MultiLayer Switching v1.11 – Aaron Balchunas
The configuration of router-on-a-stick was demonstrated earlier in this
section. Unfortunately, there are inherent disadvantages to router-on-a-stick:
• There may be insufficient bandwidth for each VLAN, as all routed
traffic will need to share the same router interface.
• There will be an increased load on the router processor, to support the
ISL or DOT1Q encapsulation taking place.
A more efficient (though often more expensive) alternative is to use a
multilayer switch.
Configuration of inter-VLAN routing on a multilayer switch is simple. First,
create the required VLANs:
Switch(config)# vlan 101
Switch(config-vlan)# name VLAN101
Switch(config)# vlan 102
Switch(config-vlan)# name VLAN102
Then, routing must be globally enabled on the multilayer switch:
Switch(config)# ip routing
Next, each VLAN SVI is assigned an IP address:
Switch(config)# interface vlan 101
Switch(config-if)# ip address 192.168.1.1 255.255.0.0
Switch(config-if)# no shut
Switch(config)# interface vlan 102
Switch(config-if)# ip address 10.1.1.1 255.255.0.0
Switch(config-if)# no shut
These IP addresses will serve as the default gateways for the clients on each
VLAN. By adding an IP address to a VLAN, those networks will be added
to the routing table as directly connected routes, allowing routing to occur.
* * *
All original material copyright © 2009 by Aaron Balchunas (aaron@routeralley.com),
unless otherwise noted. All other material copyright © of their respective owners.
This material may be copied and used freely, but may not be altered or sold without the expressed written
consent of the owner of the above copyright. Updated material may be found at http://www.routeralley.com.
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