Implementation InformationIn Dell Networking OS, prefix lists are used in processing routes for routing protocols (for example, router information protocol [RIP], openshortest 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 BGP modes.Create the prefix list in PREFIX LIST mode and assign that list to commands in ROUTER RIP, ROUTER OSPF 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 Command Line 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] [le max-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 to permit all routes (permit0.0.0.0/0 le 32). The “permit all” filter must be the last filter in your prefix list. To permit the default route only, enter permit0.0.0.0/0.The following example shows how the seq command orders the filters according to the sequence number assigned. In the example, filter20 was configured before filter 15 and 12, but the show config command displays the filters in the correct order.Dell(conf-nprefixl)#seq 20 permit 0.0.0.0/0 le 32Dell(conf-nprefixl)#seq 12 deny 134.23.0.0 /16Dell(conf-nprefixl)#seq 15 deny 120.23.14.0 /8 le 16Dell(conf-nprefixl)#show config!ip prefix-list jubaseq 12 deny 134.23.0.0/16Access Control Lists (ACLs) 129
