VLAN Questions

Jun 17, 2010 4 Replies

I am setting up VLANs for each floor plus one for the servers. All the servers will be connected to a separate switch, which is connected to a 4507 that will will do all the routing.


  1. Should the server switch ports be configured as access or trunk?
  2. Whatever VLANs are carried by a trunk, do those VLANs need to be configured on the switches on both sides of the trunk? For example, none of the floor switches are directly connected to the server switch. Do the floor switches need to be configured with the server VLAN?

I am setting up VLANs for each floor plus one for the servers. All the servers will be connected to a separate switch, which is connected to a 4507 that will will do all the routing.

  1. Should the server switch ports be configured as access or trunk?
  2. Whatever VLANs are carried by a trunk, do those VLANs need to be configured on the switches on both sides of the trunk? For example, none of the floor switches are directly connected to the server switch. Do the floor switches need to be configured with the server VLAN?

They should be all access ports. Trunk ports usually are for switch to switch connections. Of course, there are exceptions, or even common use in some environments (ESX comes to mind), but in general this is how things go.

Yes, all switches as part of that layer-2 network need to be configured with all the VLANs that exist. If you have 3 switches in a row, the middle switch will need all the VLANs in use to trunk through, even if no access ports for those VLANs exist on it.

So if two switches are connected by a router and switch1 has access ports on VLAN 101 and switch2 has access ports on VLAN 102, both VLANs end at the router? This makes sense if the rule is "VLANs do not span different layer-2 networks". Is this true?

it is a design issue - but often the entire reason for going "through" a router is to limit layer 2 traffic.

golden rule with VLANs is they should only go where they need to.

many campus network issues come down to sprawling uncontrolled vlan structures

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