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Advanced Concepts

Introduction​

This page presents the advanced BGP routing features available on the Cloud Temple Internet infrastructure.

BGP Communities​

Cloud Temple offers a variety of BGP communities to control the path selection used by your traffic.

What is a BGP Community?​

BGP communities are optional attributes that can be attached to BGP routes to mark, filter, or influence routing.

Actions on Local Preference​

The following BGP communities allow you to modify the local preference of your prefixes, thereby influencing the path selection toward the machine announcing the prefix within AS33930.

You can adjust the local preference of a prefix within the Cloud Temple Internet backbone in AS 33930 by using the following communities:

BGP CommunityPriorityLocal Preference
33930:40010Low priority10
DefaultCloud Temple Backbone (default)100
33930:40150Medium priority150
33930:40200High priority200
33930:40250Maximum priority250

Note: The higher the local preference value, the more preferred the path is in BGP routing decisions. By default, without a specific community, your prefixes use the standard local preference of 100.

Configuration​

To apply a BGP community to your announcements:

  1. Define a policy that tags the prefix with the community
  2. Apply this policy to the BGP session with Cloud Temple route servers

Example configuration (bird)​

# Define a policy that tags the prefix with the community
filter p_bkb_rs_001_export {
    if net ~ [203.0.113.0/32]
    then {
        bgp_community.add((33930, 40250));
        accept;
    }
    if net ~ [203.0.113.1/32]
    then {
        accept;
    }
    else reject;
}

# Apply this policy to the BGP session with Cloud Temple route servers
protocol bgp p_bkb_rs_001 {
        local 100.64.3.226 as 65551;
        neighbor 100.64.0.1 as 33930;
        multihop;
        keepalive time 10;
        hold time 30;
        ipv4 {
                export filter p_bkb_rs_001_export;
        };
}

The prefix 203.0.113.0/32 will be advertised with a local preference of 250, and the prefix 203.0.113.1/32 will be advertised with a local preference of 100 (default) within AS33930.