Netgear XCM8810 Chassis User Manual - Page 670

NETGEAR 8800 User Manual Routing Table The routing table in a router using RIPng contains an entry for every known destination network. Each routing table entry contains the following information: • IP address and prefix length of the destination network • Metric (hop count) to the destination network • IP address of the next hop router, if the destination is not directly connected • Interface for the next hop • Timer that tracks the amount of time since the entry was last updated • A flag that indicates if the entry is a new one since the last update • The source of the route, for example, static, RIPng, OSPFv3, etc. The router exchanges an update message with each neighbor every 30 seconds (default value), or when there is a change to the overall routed topology (also called triggered updates). If a router does not receive an update message from its neighbor within the route timeout period (180 seconds by default), the router assumes the connection between it and its neighbor is no longer available. Split Horizon Split horizon is a scheme for avoiding problems caused by including routes in updates sent to the router from which the route was learned. Split horizon omits routes learned from a neighbor in updates sent to that neighbor. Poison Reverse Like split horizon, poison reverse is a scheme for eliminating the possibility of loops in the routed topology. In this case, a router advertises a route over the same interface that supplied the route, but the route uses a hop count of 16, which defines that router as unreachable. Triggered Updates Triggered updates occur whenever a router changes the metric for a route. The router is required to send an update message immediately, even if it is not yet time for a regular update message to be sent. This generally results in faster convergence, but may also result in more RIPng-related traffic. Route Advertisement of VLANs Virtual LANs (VLANs) that are configured with an IP address but are configured to not route IP or are not configured to run RIP, do not have their subnets advertised by RIP. RIP advertises only those VLANs that are configured with an IP address, are configured to route IP, and run RIP. 670 | Chapter 23. RIPng