VLAN and Subnet

[Leonlei]

I have a quesiton about the relationship between and Subnet. Assuming there are two VLANs 20 and 30 have been configured on a L3 switch, vlan 20 is 192.168.1.0/24 and vlan 20 is 172.16.1.0/24. If I move a server(172.16.1.100) from vlan 20 to 30 without changing IP address, is there any way to keep the communication between the clints in vlan 20 and this server? How does routing work?

[m.stricker]

If you move a machine into vlan 20 without changing the IP address, no host in either VLAN will be able to communicate with it. Every host in a vlan must have the same subnetid for communication to occur, and each vlan must have a unique Subnet Id or for routing to work properly.

Routing between VLAN's is a big subject. Search for "Router-on-a-stick" or "Inter-VLAN routing" on the Cisco Web site.

[almetcousins]

If a host of vlan 20 try to comunicate with your server the request will go to the rsm of your switch (since is in different subnet) the rsm then will send the request to vlan 30 and nobody will answer because your server is no longer in vlan 30. The only thing i can think of is creating a subnet for your server in the 172.16.1.100 range, assign and ip in the vlan 30 interface and change the default gateway of your server to that ip. But the easier and cleaner way is to just change IP :)

Regards