VLAN INTERVIEW QUESTIONS

1. Will broadcast traffic on one VLAN reach another VLAN

No. VLANs are used to segregate broadcast traffic.

2. Which is the vendor neutral standard used for VLAN Tagging

802.1q

3. Which field in a TCP/IP header does vlan tagging occur.

It occurs in the data link layer. VLAN tag information is inserted in the frame header.

4. Which VLAN protocol can be used for connecting between Cisco switches.

ISL.


5. Where is native vlan used ?

It is used when a specific vlan traffic need not be sent over a trunk port which carries multiple vlans.

6. Is a router required for communicating between vlans ?

Yes it is required. VLAN’s logically create different networks. Inter vlan routing , is performed using routers for communication between VLAN’s.

7. Do all switches support vlans ?

Switches are of two types , which are manageable and unmanageable. VLAN’s are supported only on manageable switch.

8. How do switches understand mac-addresses of systems belonging to different VLANS ?

Using VLAN mac-address table.


9. A switch support has to carry traffic for multiple vlans. How type of port configuration would you perform

The port has to be configured as trunk port.

10. Can two vlans be assigned with two subnets from the same major network.

Vlans are used for segregating networks. So two subnets irrespective of whether they are from the same of different major networks can be used with two vlans

11. In an 802.1q encapsulated ethernet frame, which field contains the value of the upper layer protocol

802.1q frames are used for carrying vlan tagged frames. The 802.1q header is inserted in the ethernet frame. The ethernet frame contains a field called type value which would indicate the type of upper layer protocol like IP, IPX etc.

12.On a layer 2 switch, port 1 is a member of vlan 2 and port 2 is a member of vlan 3. Two computers, PC1 and PC2 are connected to the ports. The IP addresses of the computers are 192.168.1.2 /24 and 192.168.1.3/24. Both the computers belong to the same network address of 192.168.1.0/24. If PC1 pings PC2, would a response be received.

A response would not be received. Although both the computers belong to the same network address of 192.168.1.0/24, there are connected to ports on the switch which are members of different vlans. For communication between vlans, a router is required.