Dell PowerConnect B-RX BigIron RX Series Configuration Guide v02.7.02 - Page 837

Changing the default metric used for redistribution 26 Changing the default metric used for redistribution The device can redistribute directly connected routes, static IP routes, RIP routes, ISIS routes, and OSPF routes into BGP4. By default, BGP uses zero (0) for direct connected routes and the metric (MED) value of IGP routes in the IP route table. The MED is a global parameter that specifies the cost that will be applied to all routes, if assigned, when they are redistributed into BGP4. When routes are selected, lower metric values are preferred over higher metric values. The default, the BGP4 MED value is not assigned. NOTE RIP, ISIS, and OSPF also have default metric parameters. The parameters are set independently for each protocol and have different ranges. To change the default metric to 40, enter the following command. BigIron RX(config-bgp)# default-metric 40 Syntax: default-metric The indicates the metric and can be a value from 0 - 4294967295. Changing administrative distances BigIron RX can learn about networks from various protocols, including the EBGP portion of BGP4 and IGPs such as OSPF, ISIS, and RIP. Consequently, the routes to a network may differ depending on the protocol from which the routes were learned. To select one route over another based on the source of the route information, the device can use the administrative distances assigned to the sources. The administrative distance is a protocol-independent metric that IP routers use to compare routes from different sources. The device re-advertises a learned best BGP4 route to the BigIron RX's neighbors even when the route table manager does not also select that route for installation in the IP route table. The best BGP4 route is the BGP4 path that BGP selects based on comparison of the paths' BGP4 route parameters. Refer to "How BGP4 selects a path for a route" on page 740. When selecting a route from among different sources (BGP4, OSPF, RIP, ISIS, static routes, and so on), the software compares the routes on the basis of each route's administrative distance. If the administrative distance of the paths is lower than the administrative distance of paths from other sources (such as static IP routes, RIP, or OSPF), the BGP4 paths are installed in the IP route table. Here are the default administrative distances on the device: • Directly connected - 0 (this value is not configurable) • Static - 1 is the default and applies to all static routes, including default routes. This can be assigned a different value. • EBGP - 20 • OSPF - 110 • ISIS - 115 • RIP - 120 • IBGP - 200 • Local BGP - 200 BigIron RX Series Configuration Guide 765 53-1001810-01