ER BGP Default originate

From JuniperClue

Problem

Currently, it is extremely difficult to originate a default route via BGP. Using a policy-statement is overly complicated, and requires that a default route exist on the router. Even if a default route does exist, many users mark it "no-readvertise" so that it is not accidentally matched by other announcement/redistribution policies. This means that in order to advertise a default route to a specific BGP neighbor, you must have a static route capable of being readvertised, and make explicit exceptions for it in all other announcement/redistribution policies.

An example of the configuration statements necessary to support originating a default route via BGP is:

routing-options {
    static {
        route 0.0.0.0/0 discard;
    }
}
policy-options {
    policy-statement igp-redistribute {
        term exclude-default {
            from {
                route-filter 0.0.0.0/0 exact;
            }
            then reject;
        }
        ...
    }
    ...potentially other redistribution policies...
    policy-statement default-originate {
        term default {
            from {
                route-filter 0.0.0.0/0 exact;
            }
            then accept;
        }
        then next policy;
    }
}
protocols {
    bgp {
        group example {
            neighbor 1.2.3.4 {
                remote-as 1234;
                export [ bgp-originate other-export-policies ... ];
            }
        }
    }
}

Obviously, this is both complicated and more likely to result in accidental misconfigurations.

Solution

Add a specific BGP neighbor flag that injects a default route, regardless of the existence of the default route on the router. This is also the way that Cisco and most other platforms handle this problem, which reduces the Juniper learning curve for other users.

Minimal example:

protocols {
    bgp {
        group example {
            neighbor 1.2.3.4 {
                remote-as 1234;
                default-originate;
            }
        }
    }
}

Potentially more complex example:

protocols {
    bgp {
        group example {
            neighbor 1.2.3.4 {
                remote-as 1234;
                default-originate {
                    metric 50;
                    community 4321:1234;
                    other BGP parameters;
                }
            }
        }
    }
}

Another potential solution:

policy-options {
    policy-statement default-originate-params {
        then {
            metric 50;
            community 4321:1234;
            other BGP parameters;
        }
    }
}
protocols {
    bgp {
        group example {
            neighbor 1.2.3.4 {
                remote-as 1234;
                default-originate default-originate-params;
            }
        }
    }
}