 VLAN Configuring SVIs 200, which does not exist on our switch, will still result in the SVI being created. We can even assign an IP address to the interface, and enable it with the no shutdown command: Cat-3550(config)# interface Vlan200 1w5d: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan200, changed state to down Cat-3550(config-if)# ip address 10.200.0.1 255.255.255.0 Cat-3550(config-if)# no shut The interface will initially be down/down because there is no VLAN at layer two to support it. The hardware type is EtherSVI, indicating that this is a logical SVI: Cat-3550# sho int vlan 200 Vlan200 is down, line protocol is down Hardware is EtherSVI, address is 000f.8f5c.5a00 (bia 000f.8f5c.5a00) Internet address is 10.200.0.1/24 MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set ARP type: ARPA, ARP Timeout 04:00:00 Last input never, output never, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes): Total output drops: 0 Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts (o IP multicast) 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 packets output, 0 bytes, 0 underruns 0 output errors, 0 interface resets 0 output buffer failures, 0 output buffers swapped out Once we add VLAN 200 to the switch, the interface comes up: Cat-3550(config)# vlan 200 Cat-3550(config)# 1w5d: %LINEPROT0-5-UPDOWN: Line protocol on Interface Vlan200, changed state to up Cat-3550# sho ip int brie I include Vlan200 Vlan200 10.200.0.1 YES manual up We have not assigned any ports to this VLAN, but the SVI for the VLAN is up and operating at layer three. We can even ping the new interface: Cat-3550# ping 10.200.0.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.200.0.1, timeout is 2 second