BGP Communities
Enabling Customers to Take Control of Their Traffic Flows
- AFN's IP transit network offers a range of BGP Community options to help control the scope of announcements and path selection.
Notes & Disclaimer
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- Example 1: the RTBH community could be applied to all routes and drop all traffic entering the AFN network causing loss of connectivity for your network.
- Example 2: the “Do Not Advertise” community is advertised to all but one of AFN’s peers and that one peer has an outage potentially causing an outage for your network.
- These communities and tools are subject to change without notice.
- These are provided on a best effort basis and not subject to product-specific SLAs.
Prepends and Do Not Announce
- IP Transit customers can use predefined communities to prepend or deny announcements to specific AFN peers. Communities modify route advertisements at exit points of the AFN network.
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When multiple communities are used, they will be applied in priority order. The order of priority, from highest to lowest:
- Do Not Announce
- 4 prepends
- 3 prepends
- 2 prepends
- 1 prepend
- Only the highest-priority action will be applied.
- Informational communities are added to received routes from all AFN peers. These communities can be used to verify the source of a received route.
- X is the number of prepends (x = 1, 2, 3, 4) or do NOT announce (x = 9).
- Example 1: To add 3 prepends to your advertisements to Arelion in Nashville, you would tag your advertisements to AFN with 40463:1023.
- Example 2: To troubleshoot potential network issues with AFN’s peers, you could temporarily tag the route in question with a “Do No Advertise” community to your AFN peering.
Remote Triggered Blackhole Community
- Example: If IP 1.2.3.4 was experiencing a DDoS attack that was affecting your network’s throughput limits, then either a manual route update or a DDoS response tool could create a route for 1.2.3.4/32 with community 40463:666 and advertise it to the AFN peering. This will cause the AFN network to discard all traffic destined to that IP before it enters your network.
- Warning: using the RTBH community will drop all AFN traffic to the affected IP/IPs.
Local Preference Actions
- Customers also have the option to change the default local preference setting within AS40463 (AFN IP Transit Network).
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BGP Graceful Shutdown
- AFN accepts and honors the BGP Graceful Shutdown community. The purpose of this is to reduce the amount of traffic lost when BGP sessions are to be shut down, for example, during planned work. When announced by a customer, AFN will set local-preference to 10, which will ensure the use of alternative paths, if they exist.