This section does not deal with how to segment the LAN, and it barely touches on the reasons to useswitches, bridges, or VLANs to segment your network. This section is here to verify your knowledge of the advantages of segmenting your LAN and the differences between switches and bridges.

Note The Cisco objectives list for this objective actually lists it as three separate objectives. However, for simplicity’s sake, we’ve combined these into two objectives, this one and the following.

Critical Information

As mentioned earlier, there are many reasons to segment your network, including excessive broadcasts on the network and heavy data traffic. You can use a router, you can use a switch, you can use VLANs, you can hook up two PCs and use Microsoft Windows Multihoming, you can use a bridge, you can use a multiplayer switch. All these are devices or methods for segmenting your network.

Switches and bridges both work at the Data Link layer and filter the network by hardware addresses.Layer 2 switching is considered hardware-based bridging because it uses specialized hardware called an application-specific integrated circuit (ASIC). ASICs speed can be up to gigabit with very low latency.

When a frame is received on a layer 2 device interface and the destination hardware address is unknown to the device, it will forward the frame to all connected segments. If the unknown device answers this forwarding of the frame, then the switch updates the filter table on the location of that device. However, the source address of the transmitting frame may be a broadcast address. The switch will forward all broadcasts or unknown unicasts out every interface, with the exception of the interface of arrival, by default. All devices that the broadcast is forwarded to are considered to be in the same broadcast domain.

Switches and bridges do not break up broadcast domains, and instead forward all broadcasts.

Another benefit of LAN switching over hub implementations is that one device on every segment plugged into a switch can transmit at the same time, because each segment is its own collision domain. Hubs allow only one device per network to communicate at a time.

Tip Switches cannot translate between different media types on the same segment.

Exam Essential

Know the differences between switches and bridges. Bridges create only one network, and all the devices attached to a bridge are in that network. Switches, which use VLANs, can assign each port to an individual network or VLAN.

Key Term and Concept

transparent bridging The bridging scheme used in Ethernet networks to pass frames one hop at a time. This type of bridging uses MAC addresses and is considered transparent because the source node does not know it has been bridged. The destination frames are sent directly to the end node.

Related posts:

1. Benefits of Network Segmentation With Routers
2. Advantages of LAN Segmentation
3. Network Congestion Problem in Ethernet Networks
4. Virtual LANs
5. Layered Model Exam Points
6. Spanning Tree Protocol
7. Full and Half-Duplex Ethernet Operation
8. Function of the MAC Address
9. Virtual LANs Exams Points
10. Commands to Configure Frame Relay LMIs, Maps, and Subinterfaces