• 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 apermit or deny filter in a configured prefix list.• After a route matches a filter, the filter’s action is applied. No additional filters are applied to the route.Implementation InformationIn Dell Networking OS, prefix lists are used in processing routes for routing protocols (for example, routerinformation protocol [RIP], open shortest path first [OSPF], and border gateway protocol [BGP]).NOTE: It is important to know which protocol your system supports prior to implementing prefix-lists.Configuration Task List for Prefix ListsTo configure a prefix list, use commands in PREFIX LIST, ROUTER RIP, ROUTER OSPF, and ROUTER BGPmodes.Create the prefix list in PREFIX LIST mode and assign that list to commands in ROUTER RIP, ROUTEROSPF and ROUTER BGP modes.The following list includes the configuration tasks for prefix lists, as described in the following sections.• Configuring a prefix list• Use a prefix list for route redistributionFor a complete listing of all commands related to prefix lists, refer to the Dell Networking OS CommandLine Interface Reference Guide.Creating a Prefix ListTo create a prefix list, use the following commands.1. Create a prefix list and assign it a unique name.You are in PREFIX LIST mode.CONFIGURATION modeip prefix-list prefix-name2. Create a prefix list with a sequence number and a deny or permit action.CONFIG-NPREFIXL modeseq sequence-number {deny | permit} ip-prefix [ge min-prefix-length] [lemax-prefix-length]The optional parameters are:• ge min-prefix-length: the minimum prefix length to match (from 0 to 32).• le max-prefix-length: the maximum prefix length to match (from 0 to 32).Example of Assigning Sequence Numbers to FiltersIf you want to forward all routes that do not match the prefix list criteria, configure a prefix list filter topermit all routes (permit 0.0.0.0/0 le 32). The “permit all” filter must be the last filter in your prefixlist. To permit the default route only, enter permit 0.0.0.0/0.Access Control Lists (ACLs) 117
