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Configuring the router involves some planning and decision-making along the way. You must know the details of the network where you are placing the router, the type of connectivity you want, and the configuration details of the peers to which you are connecting the router. For example, deciding whether you need to bridge rather than route a protocol over a specific interface depends on the type of network to which you are attaching the router.
Deciding the characteristics of each protocol you are routing (or bridging) over a LAN or WAN interface is based on the topology and existing characteristics of the network. For every protocol you configure to run over a LAN or WAN link, you must determine which routing protocol to use, whether to tunnel packets, whether you need or want to configure static routes, and which type of filtering to use.
This section discusses the basic concepts you must know to make the right decisions when configuring the network protocols you want to route using Novell Internet Access Server 4.1. Each network protocol you want to support must be bound and must run over a configured link.
This topic contains the following sections:
NetWare IPX and TCP/IP configurations offer options for setting the routing protocols. There are two general types of routing protocols available: distance vector and link state . Your choice of routing protocols is determined largely by which routing protocols are currently used in your network. For example, in older networks, such as NetWare 2, there might be several routers that can support only distance vector routing.
If your network contains routers that support both link state and distance vector routing, your router will need to support both. In networks that have only newer routers, it is best to configure the routers to use only link state routing protocols. In networks with older routers, you can gradually update your routers and migrate to the exclusive use of link state routing protocols.
Table 1 shows the distance vector and link state protocols that are supported by Novell Internet Access Server 4.1.
Table 1. Distance Vector and Link State Protocols
The source route bridge enables you to use your router to link token ring networks and create an extended network. Source route bridging allows end stations to discover routes dynamically and determine which one to use when sending data to any particular destination.
Novell Internet Access Server 4.1 supports concurrent routing and bridging of all major protocols, including IPX, TCP/IP, and AppleTalk, and bridges unroutable protocols, such as the IBM* NetBIOS and SNA protocols. However, because you cannot bridge and route the same protocol on the same interface, the software provides a mechanism for automatically disabling bridging for the protocols that are being routed.
NetWare Link/PPP on-demand links are WAN circuits that become active only when there is traffic on the link. Standard network protocols generally expect each WAN circuit to provide permanent connections to all remote systems. The reason is that the network protocols rely on periodic communication with remote systems to exchange routing information dynamically and, in the case of IPX, to receive service advertising updates. These periodic exchanges identify the network routes and services that are known on each remote LAN accessed over the WAN connections.
Because on-demand connections do not exchange routing or service information, both ends of the link must have enough information to be able to call each other. Because no routing traffic crosses an on-demand link, you must configure remote routes manually on the local router as static routes . This way, the connection can remain inactive until data needs to cross it.
Static routes are configured at the network protocol level, such as IPX or AppleTalk. They let the protocol know the WAN call destination to use to reach that route, as well as information about the remote router, such as IP address, number of hops, and so on.
For example, if an IP router needs to reach a remote destination, it sends packets to the local IP router that advertises the routes, and assumes the packets can reach their destination. The local router then stores the packets and, using the static route information, uses the appropriate WAN call destination to establish a connection to the remote router. After the local router completes the call and negotiates on-demand service, it forwards the stored packets to the remote router, which then forwards them to their destination.
In TCP/IP and IPX, static routes are not limited to on-demand WAN calls; you can also use them for permanent WAN calls and connections. You use a static route for a permanent WAN connection if you want to eliminate routing protocol traffic over the connection, making more bandwidth available for data, or to have a backup route for dynamic routes. You can also use static routes to limit user access to one portion of the network, or to gain access to isolated areas of the network. You can also use routed on-demand links for IPX.
Novell Internet Access Server 4.1 provides the IPRELAY and IPTUNNEL drivers for tunneling IPX packets through IP internetworks, and provides the AppleTalk Update-based Routing Protocol (AURP) to tunnel AppleTalk packets through IP internetworks.
IPRELAY is configured as a WAN board driver that simulates a collection of point-to-point Permanent Virtual Connections (PVCs) between routers. IPRELAY uses the User Datagram Protocol (UDP) encapsulation to send IPX packets through an IP internetwork to a remote IPRELAY peer. The remote IPRELAY peer then strips the UDP encapsulation and sends the IPX packet through an IPX network to its destination.
Similarly, AURP encapsulates AppleTalk packets to send them through an IP internetwork to a remote AURP peer. The remote AURP peer then strips the encapsulation and sends the packet through the AppleTalk network to its destination.
The IPTUNNEL driver enables IPX to use a TCP/IP network to communicate with other IPX nodes. The IPTUNNEL driver models the IP internetwork as a single IPX LAN. To IPX, IPTUNNEL performs the same functions as a typical NetWare LAN driver. The TCP/IP network operates as if it were a hardware network, passing packets among the IPX nodes connected to it.
Novell Internet Access Server 4.1 supports filtering to control the service and route information that is accepted or advertised by a router. Filters are useful when you want to limit specific types of traffic to certain parts of your network and when you want to provide a certain level of security. The Filter Configuration utility (FILTCFG) enables you to configure the filters for IPX, IP, AppleTalk, and the source route bridge, to selectively discard packets sent or received by a router. The following types of filters are supported:
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