Description

This article explains how to configure route aggregation and export the aggregated routes to the BGP neighbors.

Symptoms

Consider the following scenario in which you have four subnets:

  • 10.10.4.0/24
  • 10.10.5.0/24
  • 10.10.6.0/24
  • 10.10.7.0/24

The four subnets are connected to four interfaces and a fifth interface is connected to an ISP, to which we advertise the routes to the other 4 subnets. We may want to aggregate this routing information into a single route, as this reduces the amount of information the BGP has to share with its neighbors.

Solution

Configure a policy statement to specify the routes that have to be aggregated

root# set policy-options policy-statement aggregate-route from protocol direct
root# set policy-options policy-statement aggregate-route from route-filter 10.10.4.0/22 orlonger
root# set policy-options policy-statement aggregate-route then accept

[edit policy-options]
root# show
policy-statement aggregate-route {
    from {
        protocol direct;
        route-filter 10.10.4.0/22 orlonger;
    }
    then accept;
}

Aggregate the specified routes

root# set routing-options aggregate route 10.10.4.0/22 policy aggregate-route

[edit routing-options]
root# show
aggregate {
    route 10.10.4.0/22 policy aggregate-route;
}

Configure a policy statement to specify the routes that have to be exported

root# set policy-options policy-statement export-route from protocol aggregate
root# set policy-options policy-statement export-route from route-filter 10.10.4.0/22 exact
root# set policy-options policy-statement export-route then accept

[edit policy-options]
root# show
policy-statement export-route {
    from {
        protocol aggregate;
        route-filter 10.10.4.0/22 exact;
    }
    then accept;
}

Apply the policy statement in the BGP configuration

[edit protocols bgp]
root# set group session-to-AS65505 type external
root# set group session-to-AS65505 peer-as 65505
root# set group session-to-AS65505 neighbor 11.11.11.1

[edit protocols]
root# show
bgp {
    group session-to-AS65505 {
        type external;
        export export–route;
        peer-as 65505;
        neighbor 11.11.11.1;
    }
}

Modification History

2019-09-07: Removed references to J Series devices.