Dell MX9116n EMC SmartFabric OS10 User Guide - Page 517

When you configure the non-deterministic-med command, paths are compared in the order they arrive. OS10 follows this method to select different best paths from a set of paths, depending on the order they were received from the neighbors-MED may or may not get compared between the adjacent paths. By default, the bestpath as-path multipath-relax command is disabled. This prevents BGP from load-balancing a learned route across two or more EBGP peers. To enable load-balancing across different EBGP peers, enter the bestpath as-path multipath-relax command. If you configure the bgp bestpath as-path ignore command and the bestpath as-path multipath-relax command simultaneously, an error message displays-only enable one command at a time. More path support More path (Add-Path) reduces convergence times by advertising multiple paths to its peers for the same address prefix without replacing existing paths with new ones. By default, a BGP speaker advertises only the best path to its peers for a given address prefix. If the best path becomes unavailable, the BGP speaker withdraws its path from its local router information base (RIB) and recalculates a new best path. This situation requires both IGP and BGP convergence and is a lengthy process. BGP add-path also helps switch over to the next new best path when the current best path is unavailable. The Add-Path capability to advertise more paths is supported only on IBGP peers-it is not supported on EBGP peers or BGP peer groups. Ignore router ID calculations Avoid unnecessary BGP best path transitions between external paths under certain conditions. The bestpath router-id ignore command reduces network disruption that is caused by routing and forwarding plane changes and allows for faster convergence. Advertise cost As the default process for redistributed routes, OS10 supports IGP cost as MED. Both autosummarization and synchronization are disabled by default. BGPv4 and BGPv6 support • Deterministic MED, default • A path with a missing MED is treated as worst path and assigned an 0xffffffff MED value. • Delayed configuration at system boot-OS10 reads the entire configuration file BEFORE sending messages to start BGP peer sessions. 4-Byte AS numbers OS10 supports 4-byte AS number configurations by default. The 4-byte support is advertised as a new BGP capability - 4-BYTE-AS, in the OPEN message. A BGP speaker that advertises 4-Byte-AS capability to a peer, and receives the same from that peer must encode AS numbers as 4-octet entities in all messages. Layer 3 517