VMS Help TCPIP Services, Routing  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Routing allows traffic from your local network to reach its
    destination elsewhere on the internet. All hosts and gateways
    on a network use routing protocols to exchange and store routing
    information. Routing is simply the act of forwarding datagrams
    based on information stored in a routing table.

    The Compaq TCP/IP Services for OpenVMS product provides two types
    of routing:

    o  Static

       Because static routing requires manual configuration, it is
       most useful when the number of gateways is limited and where
       routes do not change frequently.

    o  Dynamic

       Dynamic routing tables use information received by means of
       routing protocol updates; when routes change, the routing
       protocol provides information on the changes. Routing daemons
       implement a routing policy, that is, the set of rules that
       decide which routes go in to the routing table. A routing
       daemon writes routing messages to a routing socket causing the
       kernel to add a new route, delete an existing route, or modify
       an existing route.

       The kernel also generates routing messages that can be read by
       any routing socket when events occur that may be of interest
       to the process, for example, the interface has gone down or a
       redirect has been received.

       Compaq TCP/IP Services for OpenVMS implements two routing
       daemons: the Routing Daemon (ROUTED) and the Gateway Routing
       Daemon (GATED).

1 - ROUTED

    ROUTED supports the Routing Information Protocol (RIP) Use
    TCPIP$CONFIG to enable ROUTED.

2 - GATED

    GATED supports interior and exterior gateway protocols. It
    obtains information from several routing protocols and selects
    the best routes based on that information.

    Before enabling GATED, you must configure the GATED protocols
    by editing the file TCPIP$GATED.CONF. Use TCPIP$CONFIG to enable
    dynamic routing.

 2.1 - GATED Protocols

    You can configure GATED to use one or more of the following
    protocols:

    Protocol               RFC        Description

    Routing Information    RFC        RIP is a commonly used interior
    Protocol (RIP)         1058,      protocol that selects the route
    Versions 1 and 2       RFC 1388   with the lowest metric (hop
                                      count) as the best route.

    Open Shortest Path     RFC 1583   Another interior routing
    First (OSPF) Version              protocol, OSPF is a link-state
    2                                 protocol (shortest path first)
                                      and better suited than RIP for
                                      use in complex networks with
                                      many routers.

    Exterior Gateway       RFC 904    EGP exchanges reachability
    Protocol (EGP)                    information between autonomous
                                      systems. An autonomous system
                                      is usually defined as a set
                                      of routers under a single
                                      administration, using an
                                      interior gateway protocol and
                                      common metric to route packets.
                                      Autonomous systems use exterior
                                      routing protocols to route
                                      packets to other autonomous
                                      systems.

    Border Gateway         RFCs       Like EGP, BGP exchanges
    Protocol (BGP)         1163,      reachability information
                           1267,      between autonomous systems
                           1654       but supports nonhierarchical
                                      topologies. BGP uses path
                                      attributes to provide more
                                      information about each route.
                                      Path attributes can include,
                                      for example, administrative
                                      preferences based on political,
                                      organizational, or security
                                      considerations.

    Router Discovery       RFC 1256   This protocol is used to inform
                                      hosts of the availability of
                                      hosts it can send packets to
                                      and to supplement a statically
                                      configured default router.