Switch, Route, or ?

[wrwiii122]

I have 20 3550's in a loop throughout a 50 mile span. They are looped by the GBICs using fiber. Right now there are 4 Vlans all isolated from each other. At this point I need to put cameras in each of these locations which is going to add alot of bandwidth. My question is, do I add another VLAN and let all the traffic go over it with 150 IPs or do I move to L3? If I move to L3 does the 3550 route between VLANS or by IP subnet? Also can I keep the original 4 VLANS out of the routing loop so that they can still be isolated.

Thanks in advance

[lgijssel]

When we discuss routing, this is generally ip routing. When the term vlan routing is used it means that we route the ip ranges (L3) that were assigned to vlans (L2). The L2-L3 connection is made through configuring vlan interfaces on your L3switch/router.

In general I am not particularly fond of vlans that span multiple locations in a MAN or WAN because this means spanning tree is always involved. It is a better approach to keep the vlans local and use ip routing to connect sites.

For your network I would always use layer3 switching (= routing) for this reason. If you do not want a vlan to be routed, you can simply omit creating the corresponding vlan interface. This will effectively disconnect the vlan from the layer3 processing.

Regards,

Leo

[wrwiii122]

The reason I have to do it like this is because I need to have 4 isolated networks that can be accessed at all locations. Is there another way? The only reason I wasn't worried about STP is because it is a gigabit connection.

[lgijssel]

The line speed does not relieve the symptoms that you get when STP becomes instable. Isolated networks can in many cases be set-up as a set of ip subnets that are interconnected through ip routing. If your app requires L2 connectivity over the MAN you should consider dumping it (at least in my opinion)

Regards,

Leo