What does local preference mean?
The LOCAL_PREF (local preference) is the first attribute a Cisco router looks at to determine which route towards a certain destination is the “best” one and deserves a spot in the router’s routing table.
Is local preference advertised?
When an autonomous system (AS) has multiple routes to another AS, the local preference indicates the degree of preference for one BGP route over the other BGP routes. The LOCAL_PREF path attribute is always advertised to IBGP peers and to neighboring confederations. It is never advertised to external BGP (EBGP) peers.
How does BGP detect local preferences?
BGP attribute local preference is the second BGP attribute and it can be used to choose the exit path for an autonomous system. Here are the details: Local preference is the second BGP attribute. You can use local preference to choose the outbound external BGP path.
Is BGP a layer 3 protocol?
For the most part, routing is a layer-3 function, but, as you pointed out, BGP uses a layer-4 protocol to communicate with other BGP speakers in order to do what is normally considered a layer-3 function. Many network protocols fall into a gray area, or are considered in one layer while using another layer.
What you should know about BGP’s local_Pref?
The BGP local preference attribute is the second BGP attribute and is used to choose the exit path for an autonomous system . The local preference has to be set inbound on routes being received to influence the outbound routing behaviour. A higher local preference is preferred and the default is 100. The BGP Local Preference attribute or local-pref is used to influence the outbound routing decision of a router running BGP.
What is the default route preference for BGP?
By default, the routing software assigns a preference of 170 to routes that originated from BGP. Of all the routing protocols, BGP has the highest default preference value, which means that routes learned by BGP are the least likely to become the active route.
What is local preference?
Local Preference is one of the ways to alter the path taken by one AS to reach another AS. The difference between Local Preference and Weight is that Weight is just locally signifant in the router while Local Preference is what I call “Local AS significant”.
What is the BGP path selection process?
BGP path selection process BGP routers use Cisco’s best path algorithm to determine the best route to an AS, which is then stored for future reference. To determine the best path to an AS, the algorithm compares each valid path with all other paths in a routing table according to the following criteria: