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Configure the BGP identifier range for a Cloud Router

Each Cloud Router has a BGP identifier, also known as a router ID. The BGP identifier is unique to each Cloud Router in your Virtual Private Cloud (VPC) network as required by RFC 6286. A BGP identifier is a 4-octet unsigned integer, represented as a valid IPv4 address.

You can assign an explicit BGP identifier range to your Cloud Router. If you do, your Cloud Router is assigned a stable BGP identifier from the assigned range.

An explicit BGP identifier range is required for IPv6 BGP. If you add an IPv6 interface to a Cloud Router that doesn't already have a BGP identifier range assigned, a random range from the IPv4 link-local address space is assigned to it.

A Cloud Router without an explicit BGP identifier range is assigned a BGP identifier corresponding to the lexicographically-last IPv4 address among its IPv4 interfaces.

BGP identifier changes and BGP session restarts

Unless you've configured an explicit BGP identifier range, Cloud Router might change the automatically generated router ID in the following circumstances:

Before you begin

gcloud

If you want to use the command-line examples in this guide, do the following:

  1. Install or update to the latest version of the Google Cloud CLI.
  2. Set a default region and zone.

API

If you want to use the API examples in this guide, set up API access.

Assign a BGP identifier range to Cloud Router

This section describes how to assign an explicit BGP identifier range to a Cloud Router.

Console

  • In the Google Cloud console, go to the Create a Cloud Router page.

    Go to Create a Cloud Router

    • Specify the Cloud Router's details:

  • Optional: To specify custom advertised routes, go to the Advertised routes section. For more information, see Advertised routes.
    1. To specify custom Routes, select Create custom routes.
    2. Choose whether to advertise the subnets visible to the Cloud Router. Enabling this option mimics the Cloud Router's default behavior.
    3. To add an advertised route, select Add a custom route, and then configure it.
  • To save your settings and create a Cloud Router, click Create. Your new Cloud Router appears on the Cloud Router listing page. To view its details and to configure a BGP session, select it.

    • gcloud

    To assign an explicit BGP identifier range when you create the Cloud Router, use the --bgp-identifier-range flag.

    gcloud compute routers create ROUTER_NAME \
    --bgp-identifier-range=BGP_IDENTIFIER_RANGE

    Replace BGP_IDENTIFIER_RANGE with a link-local IPv4 range from 169.254.0.0/16 with a subnet mask prefix length of at most /30. The IPv4 address range must not overlap either of the following:

    API

    Use the routers.insert method:

        POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/routers/ROUTER_NAME
    {
      "bgp": {
         "asn": "ASN_NUMBER",
         "keepaliveInterval": KEEPALIVE_INTERVAL,
         "identifierRange": BGP_IDENTIFIER_RANGE
      },
      "name": "ROUTER_NAME",
      "network": "NETWORK"
     }

    Replace BGP_IDENTIFIER_RANGE with a link-local IPv4 range from 169.254.0.0/16 with a subnet mask prefix length of at most /30. The range must not overlap with any existing IPv4 Cloud Router interface or a BGP identifier range of a Cloud Router in the same region.

    Modify the BGP identifier range

    This section describes how to modify an existing explicit BGP identifier range on a Cloud Router.

    gcloud

    To change the explicit BGP identifier range, run the following command.

    gcloud compute routers update ROUTER_NAME \
    --bgp-identifier-range=BGP_IDENTIFIER_RANGE

    Replace BGP_IDENTIFIER_RANGE with a link-local IPv4 range from 169.254.0.0/16 with a subnet mask prefix length of at most /30.

    The IPv4 address range must not overlap either of the following:

    • The IPv4 address range used by another BGP session on this Cloud Router.

    • Any custom BGP identifier range used by another Cloud Router in the same VPC network and region.

    API

    Use the routers.patch method to update the bgp.identifierRange field:

        PATCH https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/routers/ROUTER_NAME
    {
      "bgp": {
        "identifierRange": BGP_IDENTIFIER_RANGE
     }
   }

    Replace BGP_IDENTIFIER_RANGE with a link-local IPv4 range from 169.254.0.0/16 with a subnet mask prefix length of at most /30. The IPv4 address range must not overlap either of the following:

    • The IPv4 address range used by another BGP session on this Cloud Router.

    • Any custom BGP identifier range used by another Cloud Router in the same VPC network and region.

    What's next