1 IP subent for 2 VLANs? Possible?

Question

Hi Sir,
I have a few questions on Vlan and IP subnet.
Q1. Can I have one subnet used on 2 Vlans? From my understanding, it is recommended to have one IP subnet used for one VLAN.
Q2. If I can use 1 IP subnet which has a prefix of /23 for 2 VLANs, then under what circumstances that we have to use this approach?
Q3.How can I use 1 IP subnet for 2 VLANs? Any sample of configuration guide?
Thank you.
Regards,
Delon

Answer 1

Delon,
basically what you are going to do to make this work is take a L3 switch and build the two vlans you want (will refer to them as X and Y) in the SUP
Example:
console (enable) set vlan x name x state active
vlan x created
console (enable) set vlan y name y state active
vlan y created
Now you are going to get into the layer 3 portion of the L3 device, whatever that may be, and assuming you are using 1 class C subnet for your IP space, your command structure would look something like this
(# = whatever IP structure you want to use)
router#(config) int vlan x
router#(config-int) ip add #.#.#.1 255.255.255.128
router#(config-int) no shut
router#(config-int) int vlan y
router#(config-int) ip add #.#.#.129 255.255.255.128
router#(config-int) no shut
again, this is a very basic configuration! Depending on the piece of equipment you are trying to configure this on... you should do some research on intervlan routing. 9 times out of 10 depending on the equipment, you will find step by step procedures more taylored to your needs