Chapter 10


What is microsegmentation?


Answer: Microsegmentation is the capability of treating a small number of hosts, or nodes, as a single physical segment or collision domain. Microsegmentation can be accomplished with a switch, because a switch treats each port as its own segment.


What are the three basic components of a switched network?


Answer: A switched network is composed of three basic components: physical switching platforms, a common software infrastructure, and network management tools.


What is a flat network?


Answer: A flat network is one Layer 2 network segment. It is a network in which all attached devices can reach each other without going through any intermediary hardware devices, such as a router. A VLAN is an example a flat network.


Name the most significant problem inherent in a flat network?


Answer: A flat network is a single broadcast domain, and because every host on the network must process every frame it receives, each host must process each broadcast frame it receives to determine whether it is the intended recipient. In a larger network with numerous broadcasts, this results in wasted processor time on each host, and contention for network bandwidth, because while the broadcasts are using the network, no one else can.


What are some of the features available to you in a VLAN implementation?


Answer: VLANs provide you a means to extend a LAN beyond its local geography. VLANs also enable you to group users together based on function, such as creating a virtual LAN for different departments within an organization, regardless of their physical proximity to each other.


What are some of the issues you need to address in a mixed-media environment, such as mixing Token Ring and Ethernet LANs?


Answer: Two factors need to be addressed in a mixed-media environment. The first factor is the minimum and maximum frame size each media is capable of supporting, and determining the lowest common denominator for each medium used. The second factor that needs to be considered regarding mixed-media networks is that switches must use a translation function to switch between different media, and this translation function can result in problems such as converting the MAC address among the different media.


What are some general principles of network design?


Answer: Some general network design principles are as follows:

- Examine your network for single points of failure, implementing redundant hardware or links when necessary.

- Characterize the applications that are using your network and the protocol traffic these applications create.

- Analyze the bandwidth usage on your network, ensuring there is enough available bandwidth for all network users.

- Build your network using a hierarchical or modular model, so that as your network grows, you can add the necessary parts, rather than undertaking major redesign effort.


What are some principles of switched LAN design?


Answer: Switched LAN design principles include the following:

- Contain broadcast radiation containment.

- Ensure your VLANs are moving network traffic in an efficient manner, minimizing hops between source and destination network segments.

- Ensure you have enough available bandwidth to support routing functionality in your network.

- Ensure you have placed administrative boundaries in the appropriate place(s) within the network.


What are some of the network services offered by routers that are not available with switches alone?


Answer: Routers provide broadcast and multicast control and segmentation in the network by filtering messages from being forwarded to any other network. Routers also provide the following functions: media transition, such as between Token Ring and Ethernet; transition between the different media types of each network; determination of where traffic goes based on the network (OSI Layer 3) address, not the MAC (OSI Layer 2) address.


What is the difference between ARP and RARP?


Answer: Reverse Address Resolution Protocol (RARP) allows a physical machine in a local-area network to request its IP address from a gateway server's Address Resolution Protocol (ARP) table or cache. (RARP is confined to a broadcast domain, as opposed to Bootstrap Protocol [BOOTP], which can cross routers.)


Is there a "one size fits all" concept for network design?


Answer: No. Network designs are unique based on several factors and, as such, there is no "one size fits all" network design.