Border Gateway Protocol (BGP)

COMMUNITY

A community is a group of routes that have the same routing policies applied to them. This saves time and resources. A community is defined by the COMMUNITY attribute of a BGP route.

The FortiGate unit can set the COMMUNITY attribute of a route to assign the route to predefined paths (see RFC 1997). The FortiGate unit can examine the COMMUNITY attribute of learned routes to perform local filtering and/or redistribution.

The BGP commands related to COMMUNITY include:

config router bgp

set send-community {both | disable | extended | standard}

end

 

NEXT_HOP

The NEXT_HOP attribute says what IP address the packets should be forwarded to next. Each time the route is advertised, this value is updated. The NEXT_HOP attribute is much like a gateway in static routing.

FortiGate units allow you to to change the advertising of the FortiGate unit’s IP address (instead of the neighbor’s IP address) in the NEXT_HOP information that is sent to IBGP peers. This is changed with the config neighbor, set next-hop-self command.

The BGP commands related to NEXT_HOP include:

config router bgp config neighbor

set attribute-unchanged [as-path] [med] [next-hop]

set next-hop-self {enable | disable}

end end

 

ATOMIC_AGGREGATE

The ATOMIC_AGGREGATE attribute is used when routes have been summarized. It indicates which AS and which router summarize the routes. It also tells downstream routers not to de-aggregate the route. Summarized routes are routes with similar information that have been combined, or aggregated, into one route that is easier to send in updates. When it reaches its destination, the summarized routes are split back up into the individual routes.

Your FortiGate unit doesn’t specifically set this attribute in the BGP router command, but it is used in the route map command.

The commands related to ATOMIC_AGGREGATE include:

config router route-map edit <route_map_name>

config rule

edit <route_map_rule_id>

set set-aggregator-as <id_integer>

set set-aggregator-ip <address_ipv4>

set set-atomic-aggregate {enable | disable}

end end

end

6 thoughts on “Border Gateway Protocol (BGP)

  1. piccolo

    Hi Mike,
    if i configure the following on fortigate1:
    config router bgp
    set as 65000
    set router-id 10.2.2.254
    config neighbor
    edit “10.2.2.253”
    set next-hop-self enable
    set remote-as 65000
    set send-community6 disable
    next

    config redistribute “static”
    set status enable
    end

    fortigate2 should get the default route 0.0.0.0 0.0.0.0 from fortigate1 as it is static ?

    how can i redistribute the default route(fortigate1) to fortigate2 ?

    thanks
    regards

    Reply
    1. Mike Post author

      There is a really good KB article that explains how to do this. You can find it here

      If you want to redistribute static routes you would enable the following

      config router bgp
      config redistribute static
      set status enable
      end
      end

      An example of the config would be like this

      config router prefix-list
      edit “only_dflt”
      config rule
      edit 1
      set prefix 0.0.0.0 0.0.0.0
      unset ge
      unset le
      next
      end
      next
      end

      config router route-map
      edit “only_default_route”
      config rule
      edit 1
      set match-ip-address “only_dflt”
      next
      end
      next
      end

      config router bgp
      set as 2
      config neighbor
      edit 10.142.0.110
      set remote-as 1
      set route-map-in “only_default_route”
      next
      end

      set router-id 10.142.0.205
      end

      Let me know if this helped answer your question!

      Thanks!

      Reply
  2. kamal

    config router bgp
    set as 65041
    set router-id 162.53.156.138
    config neighbor
    edit “10.104.55.1”
    set ebgp-enforce-multihop enable
    set soft-reconfiguration enable
    set remote-as 64699
    set send-community6 disable
    next
    edit “10.104.55.2”
    set ebgp-enforce-multihop enable
    set soft-reconfiguration enable
    set remote-as 64699
    set send-community6 disable
    next

    i am trying to accomplish above but i can see only one neighbour is establish and other is in ACTIVE state…

    Reply

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