BROCADE IP PRIMER

Chapter 8: Virtual Local Area Network (VLAN)Isn't that much prettier? And it took so much less time to do! But what aboutLayer 3 VLANs? We've got you covered. A VLAN group may have a virtual interfaceas well. Because it's a group, instead of a “ve,” we use a “group-ve”:BR-Switch#conf tBR-Switch(config)#vlan-group 1 vlan 30 to 100BR-Switch(config-vlan-group-1)#tagged e 1/1 to 1/4BR-Switch(config-vlan-group-1)#group-router-interfaceBR-Switch(config-vlan-group-1)#interface group-ve 1BR-Switch(config-vif-1)#ip address 172.18.1.1/24This virtual interface, with its IP address, will be available to VLANs 30 through100. What if some of the VLANs use different subnets? No problem. Assign thegroup-ve with multiple IP addresses:BR-Switch(config)#interface group-ve 1BR-Switch(config-vif-1)#ip address 172.18.1.1/24BR-Switch(config-vif-1)#ip address 172.22.2.1/24Here again, the router rule applies. A single interface cannot have two IPaddresses in the same subnet.Summary• A VLAN subdivides a LAN; it breaks up a broadcast domain into smallerbroadcast domains• IEEE 802.1q Frame Tagging allows a single interface to participate inmore than one VLAN• An IEEE 802.1q-tagged frame inserts a 4-byte header into the existingframe• The VLAN Identifier field is a 12-bit field inside the 802.1q-tagged header;it identifies the VLAN this particular frame belongs to; being 12-bits, theVLAN ID can be any number from 1 to 4,095• A single interface cannot be an untagged member of more than one VLAN• A single interface may be a tagged member of many VLANs• With dual-port mode, a single interface may be an untagged member ofone VLAN, and a tagged member of many VLANs• A Layer 3 VLAN allows for a router interface (or “virtual ethernet” interface)to belong to a VLAN, allowing the switch to route data into and out ofthe VLAN• A VLAN Group allows you to configure a VLAN once, but apply that configurationto many VLANs• All members of a VLAN Group will have identically-defined tagged ports188 Brocade IP Primer