IPX Routing

IPX Routing Tables

The IPX routing table is maintained by the RIP for IPX routing protocol. An entry in an IPX routing table contains the following fields:

Network Number The IPX Network Number that is matched to the destination network number in a packet's IPX header.

Forwarding MAC Address The destination MAC address of the IPX packet when it is forwarded to the next hop. For directly attached networks, the Forwarding MAC Address field is blank.

Tick Count The number of ticks it takes to reach the destination network where one tick is approximately 1/18 of a second. This estimate is based on ongoing RIP requests and replies and is determined by the transmission speed of network segments. LAN links are typically one tick, and WAN links, such as a T1 link, are usually six or seven ticks. The tick count is an estimated, not precise, measurement of delay.

Hop Count The number of routers that must be crossed to reach the IPX network number.

Interface (or Port) The interface (or network interface card) that is used when forwarding IPX traffic using this route. The router has one interface installed for each attached network segment.

Figure 5.6 shows the structure of the IPX routing table.

Enlarge figure

Figure 5.6 IPX Routing Table

If there are multiple routes to an IPX network number, IPX routers use the following process to select a route:

Select the route with the lowest number of ticks.
If there are multiple routes with the lowest number of ticks, select the route with the lowest number of hops.
If there are multiple routes with the lowest number of ticks and the lowest number of hops, the router is free to choose among the set of routes with the lowest number of ticks and the lowest number of hops.