Question of the Week 8

A network associate at NetworksHeaven needs to configure the switches and router given in the figure so that the hosts in VLAN3 and VLAN4 can communicate with eachother. Which two ethernet segments would need to be configured as trunk links?

1) A 2) B 3) C 4) D 5) E 6) F 7) G


 Answer to the Question

D and G Firstly, we should remember the following:
  •     A VLAN =  A Subnet =  A Broadcast domain
  •     Number of ports on a switch = Number of Segments = Number of Collision domains.

There are multiple segments shown in this diagram since each port of a switch is a segment.

1)  The segment between two switches should be a trunk so that it may carry traffic for multiple VLANs. VLAN trunks provide a way for one phyciscal interface to transport multiple VLANs.

2) The segment between SW-AC2 and ROUTER must be trunk so that two different VLANs can communicate using "Router on a stick" concept. VLAN 4 and VLAN 3 are two different subnets. If we want to allows communication between two different subnets (VLANs), we need a Layer 3 device (either a Router or MultiLayer Switch). Since the Switch is a Layer 2 switch, we use Router to allow communication between two different VLANs by configuring sub-interfaces on Router. The concept is well explained in this video found on youtube.