Summary routing

The route command

With the route command you can add routes to the Windows 2000 machine's routing table.  By default this table contains the following routes :

The 127.0.0.0 row contains the loopback information. The 224.0.0.0 row is used for internet broadcasting. The 255.255.255.255 is called the limited broadcast address.

The metric column contains the number of routers that must be passed + 1 to reach the destination. If there are two routes the to the same destination, the route with the lowest metric is chosen. If the metric is the same, the route with the most restrictive subnetmask is chosen.

You can use the route command to add a static route :

Route add network destination  mask  netmask gateway metric metric if interface. Use the -p option if the route should be persistant.

You can use Route print to view the current routes.

If you want to add a internet router in the routing table, use the following command structure :

Route add 0.0.0.0 mask 0.0.0.0 ip address internet gateway

The 0.0.0.0 entry will handle all addresses that cannot be handled by the other entries in the routing table. This entry is called the default route.

Protocols

RIP

Routing Information Protocol. This protocol broadcasts routing information to neighboring routers when a change in the network layout is made. At a specific periods (by default every 30 seconds) RIP sends all routing information to neighboring routers. RIP is a distance vector routing protocol which means that the route used is based on the number of hops that must be passed. It is designed for small- and medium sized networks.
Windows 2000 support RIP version 1 and version 2. The main differences between RIP version 1 and RIP version 2 are :

The main disadvantage of RIP is that it supports up to 15 hops, if more hops need to be taken the destination is reported unreachable. RIP also gives a higher chance of routing loops. When RIP advertises non-RIP-learned routers at a distance of 2 hops, even if the network is directly connected. RIP uses UPD port 520, the TTL for a RIP route is 3 minutes. If no update is receive after 3 minutes, the metric is increased to 16.

When customizing RIP you can e.g. modify the following entries :

OSPF

Open Shortest Path is a link-state routing protocol. In a link-state routing protocol, each router maintains a database of router advertisements called Link State Advertisements (LSAs). The LSA's within an autonomous system consist of a router, its attached networks, and their metrics.
The routers within an autonomous system distribute their LSA' s to their neighboring routers which store all information in a link state database (LSDB). These databases are synchronized between all neighboring routers so that each router has the same LSDB.
You can create various areas within a network. These areas will each have their own LSDB and there own area ID. If a router is within two or more areas, it keep LSDB's for each of these areas. Routers on the border of an area, connected to two or more areas, are called Area Border Routers (OBR). They advertise networks within the area to neighboring areas.
Each OSPF network has a backbone area with the area ID of 0.0.0.0. This backbone area acts as a hub for inter-area transit traffic and the distribution of routing information between areas. Inter-area traffic is routed to the backbone, then routed to the destination area, and finally routed to the destination host within the destination area. Routers on the backbone also advertise the summarized routes within their areas to the other routers on the backbone. Therefore, each router in an area has a routing table that reflects the routes available within its area and the routes corresponding to the summary advertisements of the ABR's of the other areas in the autonomous system.

OSPF uses the addresses 224.0.0.5 and 224.0.0.6 to send link update information.

The main advantages of OSPF are :

Router discovery

Windows 2000 has a new feature to automatically detect default gateways. The mechanism is called router discovery and provides more flexibility than fixed default gateways offered via DHCP or fixed addresses. Windows 2000 support router discovery as a host and as a router. Router discovery uses two types of packets :

Windows 2000 and NT 4.0 SP5 and later include host support router discovery. To activate the host function, you need to add two subkeys to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Adaptername\Parameters\Tcpip Registry key. Add the PerformRouterDiscovery subkey with a REG_DWORD value of 1, and add the SolicitationAddressBcast subkey with a REG_DWORD value of 0 (for multicast router solicitation) or 1 (for broadcast).

If you have an RRAS server participating in the discovery process as an "advertiser," you must set up RRAS by selecting IP ROUTING, then GENERAL, then choose the interface you would like to enable. From the GENERAL tab, select ENABLE ROUTER DISCOVERY ADVERTISEMENTS.

Router discovery is described in RFC 1256.

Multicast Routing

Windows 2000 Server supports a limited form of multicast routing by using a multicast proxy. This proxy can be used to provide multicast functionality for remote access users or a single LAN network connected to the Internet. One or more interfaces acts like a multicast router, while the other interface that has direct access to a true multicast router, forwards multicast traffic on behalf of the local clients.

Tools

Netsh

Netsh is a command-line and scripting tool.  You can use the RAS, Routing and Interface parts to configure and monitor RRAS.

Network monitor

Network monitor can be used to monitor network traffic at a computer's interface.

Rassrvmon

A resource kit utility to monitor details of the RRAS server.

Traceenable

A resource kit utility to trace RRAS internal components.

Windows XP/.Net improvements

More information

Microsoft support articles

Links

Last update : 5 December 2001