Friday, March 25, 2011



- Dividing a Physical Interface intoSubinterfaces
- Routing Between VLANs
- Inter-VLAN routing using a router on a stick utilizes an externalrouter to pass traffic between VLANs.
- A router on a stick is configured with a subinterface for eachVLAN and 802.1Q trunk encapsulation


Redundancy in a hierarchical network:

As businesses become increasingly dependent on thenetwork, the availability of the network infrastructurebecomes a critical business concern.
- Redundancy is the solution for achieving the necessaryavailability.
- Layer 2 redundancy improves the availability of thenetwork by implementing alternate network paths byadding equipment and cabling.



1. The VLAN Management Challenge
- As the number of switches increases on a small- or medium-sized business network, the overalladministration required to manage VLANs and trunksbecomes a challenge.

2. Small Network VLAN Management
- The figure shows a network manager adding a newVLAN, VLAN30.
- The network manager needs to update the threetrunks to allow VLANs 10, 20, 30, and 99.
- Recall that a common error is forgetting to updatethe allowed list of VLANs on trunks.

3. Larger Network VLAN Management
- After you have manually updated this network a fewtimes, you may want to know if there is a way for theswitches to learn what the VLANs and trunks are so thatyou do not have to manually configure them.
- VLAN trunking protocol (VTP).


A VLAN allows a network administrator to create groupsof logically networked devicesthat act as if they are ontheir own independent network, even if theyshare acommon infrastructure with other VLANs.

- Using VLANs, you canlogically segment switchednetworks based onfunctions,departments, or project teams. - A VLAN is a logicallyseparate IP subnetwork.


Thursday, March 24, 2011


Segmentation allows network congestion to significantly reduced within each segment. 

- LAN Segmentation with Bridges.
- LAN Segmentation with Routers.