Dell N3200-ON Networking N-Series Switches User Guide version 6.8.0 - Page 1360

5 Prefer the route with the lower MED. By default, MEDs are compared for routes from any AS, but a configuration option limits comparison of MEDs to the same AS. A route with no MED is considered to have a MED of 0. 6 Prefer an eBGP route to an iBGP route 7 Prefer the route with the lower IGP cost to the BGP NEXT HOP 8 Prefer the route learned from the peer with the lower router ID 9 Prefer the route learned from the peer with the lower peer IP address Limiting Phase 2 CPU Usage In a network with a large number of prefixes, phase 2 of the decision process can consume a significant amount of time. If the BGP hold timers are configured to be shorter than the duration of the decision process, the timers can expire causing a loss of adjacency. If the decision process runs frequently, it may consume significant CPU resources, starving other processes. Two mechanisms mitigate these potential issues. First, a hold timer prevents phase 2 from running too often. The hold time is explained in more detail in the next paragraph. Second, phase 2 is limited to running no more than approximately one second without yielding to other tasks. When an event triggers phase 2, a short delay (usually 100 ms) is imposed before the decision process runs. This delay allows other RIB changes to complete before computing new routes. When the trigger occurs, if the decision process was previously run within the hold time, the next decision process is scheduled to run after the hold time expires. The initial hold time is one second. Each time one or more new triggers occur while the hold timer is running, the hold timer is doubled, up to a maximum of 4 seconds. When the hold timer expires without BGP receiving a new phase 2 trigger, the hold time is reset to the minimum hold time. Path Attributes Dell Networking supports all path attributes described in RFC 4271. Dell Networking BGP sets the ORIGIN path attribute to IGP for routes originated through the network command and to INCOMPLETE for routes originated through route redistribution. Dell Networking BGP never sets the ORIGIN path attribute to EGP. 1360 BGP