Configuring ISL/802.1Q on an Internal Route Processor

Configuring ISL/802.1Q on an Internal Route Processor
Up until recently, the situation was that if you did not have an external router or if you had
many VLANs, you would use a Layer 3 Services Module (L3SM) to provide the layer 3 routing
for your 4000/6500 series switch.
The introduction of the Supervisor III and IV engines for the Catalyst 4000 and above changes
all this. These new Supervisor engines run IOS, and this means that they can route natively without
the need for additional hardware. Obviously, Cisco might recommend an upgrade if you are
planning much inter-VLAN routing, which is probably a good idea. The faster switching available
with these native IOS devices will certainly improve packet forwarding.
First, however, we will look at the configuration of the older design switches, which have
a native switching fabric supplemented by some sort of routing module. We will look at a
4000 series switch that has an L3SM in slot 3. Let’s first confirm the hardware configuration
of the switch:
Terry_4000> (enable) show module
Mod Slot Ports Module-Type Model Sub Status
--- ---- ----- ------------------------- ------------------- --- --------
1 1 0 Switching Supervisor WS-X4012 no ok
2 2 34 10/100/1000 Ethernet WS-X4232 no ok
3 3 Router Switch Card WS-X4232-L3 no ok
Mod Module-Name Serial-Num
--- ------------------- --------------------
1 JAE044001T8
2 JAE04271V1N
3 JAE0427155N
Mod MAC-Address(es) Hw Fw Sw
--- -------------------------------------- ------ ---------- -----------------
1 00-03-e3-7a-6b-00 to 00-03-e3-7a-6e-ff 2.1 5.4(1) 4.5(2)
2 00-02-b9-61-89-e0 to 00-02-b9-61-8a-0f 2.3
3 00-03-4a-a0-d3-ab to 00-02-4b-a0-d0-cf 1.0 12.0(7)W5( 12.0(7)
Now that we have confirmed that the switch sees the router module in port 3, we need to
access the L3SM using the session command:
Terry_4000> (enable) session 3
Trying Router...
Connected to Router.
Escape character is Q^]'.
Router>

You are now connected to the internal route processor, and you should continue to configure
the device as you would any other router. Notice in the following router output that we set the
host name and routing protocol as well:
Router>
Router>enable
Router#
Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname Terry_L3SM
Terry_L3SM(config)#router eigrp 10
Terry_L3SM (config-router)#network 172.16.0.0
As we mentioned, the route processor looks like any Cisco router, because it is running IOS.
Remember that it’s just as important to configure the routing protocols on this device as it is to
configure them on any other router. The route processor is able to handle most of the routing
protocols that a traditional router can. Be careful of large routing tables, though.