Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.100.0 - Page 196

Enabling Multipath By default, the software allows one path to a destination. You can enable multipath to allow up to 64 parallel paths to a destination. NOTE: Dell Networking recommends not using multipath and add path simultaneously in a route reflector. To allow more than one path, use the following command. The show ip bgp network command includes multipath information for that network. • Enable multiple parallel paths. CONFIG-ROUTER-BGP mode maximum-paths {ebgp | ibgp} number Filtering BGP Routes Filtering routes allows you to implement BGP policies. You can use either IP prefix lists, route maps, AS-PATH ACLs or IP community lists (using a route map) to control which routes the BGP neighbor or peer group accepts and advertises. Prefix lists filter routes based on route and prefix length, while AS-Path ACLs filter routes based on the ASN. Route maps can filter and set conditions, change attributes, and assign update policies. NOTE: Dell Networking OS supports up to 255 characters in a set community statement inside a route map. NOTE: You can create inbound and outbound policies. Each of the commands used for filtering has in and out parameters that you must apply. In Dell Networking OS, the order of preference varies depending on whether the attributes are applied for inbound updates or outbound updates. For inbound and outbound updates the order of preference is: • prefix lists (using the neighbor distribute-list command) • AS-PATH ACLs (using the neighbor filter-list command) • route maps (using the neighbor route-map command) Prior to filtering BGP routes, create the prefix list, AS-PATH ACL, or route map. For configuration information about prefix lists, AS-PATH ACLs, and route maps, refer to Access Control Lists (ACLs). NOTE: When you configure a new set of BGP policies, to ensure the changes are made, always reset the neighbor or peer group by using the clear ip bgp command in EXEC Privilege mode. To filter routes using prefix lists, use the following commands. 1 Create a prefix list and assign it a name. CONFIGURATION mode ip prefix-list prefix-name 2 Create multiple prefix list filters with a deny or permit action. CONFIG-PREFIX LIST mode seq sequence-number {deny | permit} {any | ip-prefix [ge | le] } • ge: minimum prefix length to be matched. • le: maximum prefix length to me matched. For information about configuring prefix lists, refer to Access Control Lists (ACLs). 3 Return to CONFIGURATION mode. 196 Border Gateway Protocol IPv4 (BGPv4)