Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.8.00 - Page 830

26 Configuring a switch to allow routes with its own AS number NOTE If the filter is referred to by a route map's match statement, the filter is applied in the order in which the filter is listed in the match statement. The permit | deny parameter indicates the action the router takes if the filter match is true. • If you specify permit, the router permits the route into the BGP4 table if the filter match is true. • If you specify deny, the router denies the route from entering the BGP4 table if the filter match is true. The : parameter indicates a specific community number to filter. Use this parameter to filter for a private (administrator-defined) community. You can enter up to 20 community numbers with the same command. If you want to filter for the well-known communities "LOCAL_AS", "NO_EXPORT" or "NO_ADVERTISE", use the corresponding keyword (described below). The internet keyword checks for routes that do not have the community attribute. Routes without a specific community are considered by default to be members of the largest community, the Internet. The local-as keyword checks for routes with the well-known community "LOCAL_AS". This community applies only to confederations. The device advertises the route only within the sub-AS. For information about confederations, refer to "Configuring confederations" on page 762. The no-advertise keyword filters for routes with the well-known community "NO_ADVERTISE". A route in this community should not be advertised to any BGP4 neighbors. The no-export keyword filters for routes with the well-known community "NO_EXPORT". A route in this community should not be advertised to any BGP4 neighbors outside the local AS. If the router is a member of a confederation, the device advertises the route only within the confederation. For information about confederations, refer to "Configuring confederations" on page 762. Configuring a switch to allow routes with its own AS number BGP rejects routes that contain its own AS number within its AS_PATH attribute to prevent routing loops. In an VPN hub and spoke topology this can stop legitimate routes from being accepted. In this release, the allowas-in command eliminates this problem by allowing you to set a parameter that disables the AS_PATH check function for routes learned from a specified location. To configure a switch to disable the AS_PATH check function for routes sent to it by its BGP neighbor for a maximum limit of 3 occurrences of the route, enter the following command at the BGP configuration level. BigIron RX(config-bgp-ipv4u)# neighbor 33.33.36.2 allowas-in 3 Syntax: neighbor allowas-in The variable is the IP address of the neighbor. The asn_limit value prevents loops by limiting the number of occurrences that the AS number will be accepted in routes that are received from the specified switch. The maximum limit is 10. 754 BigIron RX Series Configuration Guide 53-1002253-01