Dell Force10 S4820T S4820T Configuration Guide - Page 129

• To deny only /8 prefixes, enter deny x.x.x.x/x ge 8 le 8 • To permit routes with the mask greater than /8 but less than /12, enter permit x.x.x.x/x ge 8 le 12 • To deny routes with a mask less than /24, enter deny x.x.x.x/x le 24 • To permit routes with a mask greater than /20, enter permit x.x.x.x/x ge 20 The following rules apply to prefix lists: • A prefix list without any permit or deny filters allows all routes. • An "implicit deny" is assumed (that is, the route is dropped) for all route prefixes that do not match a permit or deny filter in a configured prefix list. • Once a route matches a filter, the filter's action is applied. No additional filters are applied to the route. Implementation Information In FTOS, prefix lists are used in processing routes for routing protocols (for example, RIP, OSPF, and BGP). Note: The S-Series platform does not support all protocols. It is important to know which protocol you are supporting prior to implementing Prefix-Lists. Configuration Task List for Prefix Lists To configure a prefix list, you must use commands in the PREFIX LIST, the ROUTER RIP, ROUTER OSPF, and ROUTER BGP modes. Basically, you create the prefix list in the PREFIX LIST mode, and assign that list to commands in the ROUTER RIP, ROUTER OSPF and ROUTER BGP modes. The following list includes the configuration tasks for prefix lists: • Configure a prefix list • Use a prefix list for route redistribution For a complete listing of all commands related to prefix lists, refer to the FTOS Command Line Interface Reference document. Configure a prefix list To configure a prefix list, use these commands in the following sequence, starting in the CONFIGURATION mode: Step Command Syntax 1 ip prefix-list prefix-name Command Mode CONFIGURATION Purpose Create a prefix list and assign it a unique name. You are in the PREFIX LIST mode. Access Control Lists (ACLs) | 129