Static Routed IP Network Design

Updated: April 30, 2010

Applies To: Windows Server 2008, Windows Server 2008 R2

A static routed IP environment is best suited to a small, single-path, static IP network:

  • A small internetwork is defined as 2 to 10 subnets.

  • Single-path means that there is only one path for packets to travel between any two endpoints on the internetwork.

  • Static means that the topology of the internetwork does not change over time.

Candidates for a static routed environment include:

  • A small business.

  • A home office IP internetwork.

  • A branch office with a single subnet.

    Rather than running a routing protocol across a typically low-bandwidth WAN link, a single default route at the branch office router ensures that all traffic not destined for a computer on the branch office network is routed to the main office.

The disadvantages of static routing are:

  • No fault tolerance. If a router or link fails, static routers cannot sense the fault and inform other routers of the fault.

    noteNote
    While this can be a concern in large corporate internetworks, a small office (with two routers and three networks based on LAN links) typically does not fail often enough to justify deploying a multipath topology and a routing protocol.

  • Administrative overhead. If a new subnet is added or removed from the internetwork, routes to the new subnet must be manually added or removed. If a new router is added, it must be properly configured for the routes of the internetwork.

Consider the following design issues before you implement static routing.

To simplify configuration, you can configure peripheral routers with a default route that points to the neighboring router. A peripheral router is a router attached to multiple networks, only one of which has a neighboring router.

We recommend that you do not configure two neighboring routers with default routes that are pointing to each other. A default route passes all traffic that is not on a directly connected network to the configured router. Two routers that have default routes pointing to each other can produce a routing loop that makes destinations unreachable.

You can implement static routing across demand-dial links in one of two ways:

  • Default route

    You can configure a default route on the branch office router that uses the demand-dial interface. The advantage of a default route is that a single route only needs to be added once. The disadvantage of a default route is that any traffic —including traffic for unreachable destinations — that is not on the branch office network causes the branch office router to call the main office.

  • Auto-static routes

    Auto-static routes are static routes that are automatically added to the routing table for a router after routes are requested across a demand-dial connection by using the RIP-for-IP routing protocol. The advantage of auto-static routes is that unreachable destinations do not cause the router to call the main office. The disadvantage of auto-static routes is that they must be periodically updated to reflect the networks that are reachable at the main office. If a new network is added to the main office and the branch office has not performed an auto-static update, all destinations on the new main office network are unreachable from the branch office.

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