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Using Multiple Autonomous Systems Numbers (ASNs) with Vultr

Last Updated: Tue, Jul 13, 2021
Networking

Introduction

With Vultr's BGP feature, you can bring your own Autonomous System Number (ASN), or Vultr can assign you a private ASN. You can use either type of ASN to peer with Vultr Cloud servers or Bare Metal servers. This guide describes how Vultr modifies the AS_PATH in different BGP routing scenarios.

About the ASNs in this Guide

Here is a reference list of the example ASNs used in this guide.

  • AS64515 is Vultr's private ASN used when peering with our VPS servers.
  • AS20473 is Vultr's public ASN, and is also used when peering with our Bare Metal servers.
  • AS65534 is an example private ASN assigned to a customer by Vultr.
  • AS64500, AS64501, and AS64502 are example public ASNs for documentation.

For the rest of this guide, private ASNs are shown in bold for clarity.

Peering Using a Public ASN

Some customers need to advertise different prefixes with different public ASNs. To do this, they usually peer using their own public ASN and then prepend the other ASNs to the AS_PATH. For example, if a customer has AS64500, and secondaries AS64501 and AS64502, the advertised prefixes to Vultr's core network could include the following AS_PATHs:

  • 64500
  • 64500_64501
  • 64500_64502
  • 64500_64501_64502

When Vultr advertises the prefix to our transit providers, we prepend our public ASN, 20473. Working from the previous example, the corresponding AS_PATHs shown on the public internet look like this:

  • 20473_64500
  • 20473_64500_64501
  • 20473_64500_64502
  • 20473_64500_64501_64502

Because the customer is peering with Vultr using AS64500, it will always appear before AS64501 and AS64502 in the path.

About Private ASNs

Customers who use a private ASN cannot prepend other ASNs.

More Information

For more information about using BGP at Vultr, see the following resources:

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