Network Segmentation

Why Segment A Network?

  • Keeps local traffic local: Breaking up a network into smaller segments reduces congestion on the network by reducing the overall traffic loads.
  • Increases the bandwidth available to each user: Bandwidth is a shared entity, but each segment and its users have full use of the bandwidth available. For example, if there are 100 users on a 100 Mbps segment, each user has an average of 1Mbps of available bandwidth. If this same segment were further segmented into 10 segments with 10 users on each segment, however, then every user would have an average of 10 Mbps of available bandwidth.
  • Fewer collisions: In general, traffic tends to stay within a segment, and less traffic is router beyond the segment to contect for access to the backbone.
  • Reduces Ethernet distance limitations: There are inherent distance limitations on an Ehternet network. When a network is segmented with a router (and only a router; not a bridge, and not a switch), the beginning point from which the maximum distance for the cabling is determined is re-established.

    • Here are some things to consider before you segment a LAN with a router:

  • A router can segment a LAN that includes different media types. For example, a LAN may have both Cat 5 and Thinnet (coaxial) cable connecting to fiber optic cabling.
  • A router can interconnect LANs that are using different protocols, provided they are all routable.
  • A router does increase latency by adding the delay caused by the router examining each packet entirely before sending it on.
  • A router can also provide more than one active link or route to a destination. On a larger LAN, this can provide route diversity and redundancy, which are always good things.

    • The Specific Benefits of Segmenting With a Router:

  • Reduced size of braodcast domains: Routers block broadcasts unless specifically instructed to forward them.
  • Smaller networks: Routers create smaller networks, as opposed to dividing a large network into smaller pieces of itself.
  • Flexible addresing: Routers segment a network by using logical, rather than physical, addresses. For example, a bridge uses the MAC or physical address to make its addressing desicions, whereas the router uses the logical or IP address.
  • Better Administration: A system administrator has more management tools available when using a router, thanks to the increased memory in a router and its ability to make routing decisions based on a multitude of factors.



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