Brocade_IP_Primer_eBook

Chapter 8: Virtual Local Area Network (VLAN)
Now, any traffic that needs to flow from 172.18.1.0/24 to 172.22.2.0/24 (and
vice versa) can travel through the router. The router has one interface
(172.18.1.1) in the Accounting VLAN, and one interface (172.22.2.1) in the
Marketing VLAN. Problem solved, right? Well, that is, until the CFO finds out
you want to spend several thousand dollars to solve the problem. Now, it
doesn't look so hot. Wouldn't it be great if you could somehow squeeze the
power of the router into your already existing switches? You can see where I'm
going with this, can't you?
What makes a VLAN a Layer 3 VLAN? Two things, really. First, you must be running
routing code (Base Layer 3 or Full Router). Second, you need to configure
a router-interface. Think of the router-interface as the physical interface on the
router we used in the previous example. This time, we'll configure it inside the
fourth floor switch (after we install routing code on it, of course).
Marketing
172.22.2.0/24
Console
49F Link 50F
1 3 5 7 9 11
13 15 17 19 21 23
25 27 29 31 33 35
37 39 41 43 45 47
Power
1F 2F 3F 4F
e1-2
e1-2
2 4 6 8 10 12
14 16 18 20 22 24
26 28 30 32 34 36
38 40 42 44 46 48
Console
49F Link 50F
1 3 5 7 9 11
13 15 17 19 21 23
25 27 29 31 33 35
37 39 41 43 45 47
Power
1F 2F 3F 4F
2 4 6 8 10 12
14 16 18 20 22 24
26 28 30 32 34 36
38 40 42 44 46 48
VLAN 20
VLAN 10
e12
5th Floor Switch
VLAN 20 VLAN 10
ve 172.22.2.1/24 ve 172.18.1.1/24
4th Floor Switch
Accounting
172.18.1.0/24
To configure the router-interfaces, we first need to declare the routerinterfaces:
BR-4thFloorSwitch#conf t
BR-4thFloorSwitch(config)#vlan 10
BR-4thFloorSwitch(config-vlan-10)#router-interface ve 10
BR-4thFloorSwitch(config-vlan-10)#vlan 20
BR-4thFloorSwitch(config-vlan-20)#router-interface ve 20
When you declare a router-interface, you use a special interface type -- ve. It
stands for virtual Ethernet. The interface you're creating doesn't physically
exist. Think of it as an interface sitting behind the VLAN, yet inside the switch.
186 Brocade IP Primer
CFO