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BGP 179 (Properties (Policy-based , it doesn't care the fastest but…

- - - - ensure that there is route in routing table of the neighbor :question:
      - ensure that the ip address in neighbor command is correct :question:
      - if the state goes between IDLE and ACTIVE, AS number may be misconfigured :warning:
    - - ensure that the source ip address or network of the packet is advertised in the IGP Table of neighboring router
      - ensure that the neighboring router has a correct neighbor statement to the router with active state
- - - - Changing the weight of all updates coming from a neighbor:
        =>> neighbor + ip address + weight [0-65535]
      - Changing the Weight using Route Map
        
        create route-map with match + PL or ACL command
        
        set weight
        
        apply the Route-map with the neighbor command
  - - - Origin(mandatory/well-known) :check:
        source of the route
        
        i => IGP=> for network originated from IGP Protocols with network command
        
        e => EGP=> for networks originated fro EGP(the precedessor of BGP)
        
        ? => incomplete=> for redistributed routes
      - AS_PATH is updated form router that advertises AS-Paths to eBGP Router and not updated between iBGP Routers and has two functions=> :check:
        
        Choose the best path based on the number of ASs in the route, begins with the neighboring AS and ends with route originating AS Number
        
        reconfigured with Route-Map and set as-path prepend
        
        prevent routing loops:
        When router receive AS_PATH carry its own AS number, it ignores this path, that makes it 100 % loopfree
      - Next-hop
        next IP Address to reach a destination
        
        for eBGP : the IP Address of the neighboring eBGP router that advertised the route
        
        for iBGP: it :warning: copys the next hop from from eBGP neighbor as it is, that is overridden by neighbor x.x.x.x next-hop-self command :check:
    - - Local-preference
        an attribute that advertised inside the AS only, to inform the router about the best route for exiting from the AS, it is configure on local routers and exchanged only between internal routers and is 100 by default, and higher is preferred.
        
        reconfigured by bgp default local-preference + value
      - Atomic aggregate
        informs the neighboring AS that the originating Router has aggregated or summarized the routes.
  - - - Aggregator(optional);
        informs about the BGP router ID and router who did the aggregation
      - Community(optional)
        allow routers to filter routes by tagging it with indicator community, and other router take decisions based on that tag. Routers that doesn't understand it forward it as it is.
    - - Multi-exit Discriminator(MED/Metric)
        to inform the external neighbors about best path into an AS/ lower is preferred/ is exchanged between ASs or eBGP Peers then they advertise it it iBGP Routers, but they don't advertise them to ASs
        
        it is the opposite of Local Preference.