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-mel beckman
Understanding AWS Bring Your Own IP (BYOIP) and AS Path Prepending
AWS BYOIP allows you to use your own public IPv4 addresses with AWS services
like EC2, Global Accelerator, and Elastic IP Addresses (EIPs). This is
particularly useful if you want to maintain brand consistency, simplify
migration, or improve IP address reputation.
BYOIP Process on AWS
1. Prerequisites:
* Your IP address range must be registered with a Regional Internet
Registry (RIR) like ARIN, RIPE, or APNIC.
* The address range should be registered to a business or institutional
entity.
* You need to provide proof of ownership and authorize Amazon to
advertise the address range.
* The addresses should have a clean history (not associated with
malicious activity).
* You must stop advertising the IP address range from other locations
before advertising it through AWS.
2. Authorization and Provisioning:
* Create a ROA: Create a Route Origin Authorization (ROA) object with
your RIR to authorize Amazon's ASNs (16509 and 14618) to advertise your IP
range.
* Generate an X.509 Certificate: Create a self-signed X.509 certificate
and add it to your RIR's RDAP record to link the IP range to your AWS account.
* Create a Signed Message: Create a signed authorization message that
includes your AWS account ID, IP address range, and an expiration date.
* Provision with AWS CLI: Use the AWS CLI to provision the IP address
range within a specific AWS region.
* Wait for Provisioning: AWS will verify the IP range and approve the
provisioning request.
3. Advertising and Allocation:
* Advertise the Range: Use the AWS CLI to advertise the IP address range
through AWS.
* Create Elastic IP Addresses: Allocate Elastic IP addresses from the
provisioned IP address pool and associate them with your AWS resources.
Using AS Path Prepending
AS path prepending is a technique used in BGP (Border Gateway Protocol) to
influence the inbound traffic routing to your network. It involves adding your
own Autonomous System Number (ASN) multiple times to the AS path in BGP
advertisements. This makes the path appear longer and less preferred to other
BGP speakers, causing them to choose alternative routes.
How to Use AS Path Prepending with AWS BYOIP:
1. Bring your ASN to IPAM: You can now bring your own ASN to IPAM and
associate it with your BYOIP CIDR.
2. Associate with BYOIP CIDR: After provisioning your ASN, associate it with
the BYOIP CIDR that you brought to AWS.
3. Advertise with your ASN: When advertising the BYOIP CIDR, choose the ASN
you brought to IPAM.
Note: While AS path prepending can be useful for influencing traffic flow,
using excessive prepending can have negative consequences, including suboptimal
routing and increased risk of route hijacking. It is generally recommended to
use BGP communities for traffic engineering when possible.
On Jun 23, 2025, at 2:43 AM, Hank Nussbacher via NANOG <[email protected]>
wrote:
Can someone explain to me how to BYOIP into AWS and use AS prepends?
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