Configure BGP for Azure ExpressRoute

Before you begin, ensure you have completed the steps outlined in Add an Azure ExpressRoute Connection to a Cloud Router.

Gather information from the PacketFabric portal

You will be asked to provide the following information:

  • Cloud Router ASN: This is the ASN you set for the PacketFabric Cloud Router. You can find this on the Cloud Router details page.

  • Private peering VLAN ID: You can find this on the BGP Settings page for the connection.

    To view the BGP Settings, click Configure BGP after the Cloud Router connection finishes provisioning:

    Screenshot of the Configure button in the PacketFabric portal

Set up private peering

From the Azure portal, refresh the ExpressRoute circuit overview page. The provider status should update to the Provisioned status:

screenshot of the expressroute circuit provider status

Click Azure private to configure a private connection to your Azure VNet.

screenshot of azure peering

Select Enable peering and then complete the following fields:

  • Row

    • Field
    • Description
  • Row

    • Peer ASN

    • Enter the ASN you set for your PacketFabric Cloud Router.

      Note that ASNs from 65515 to 65520 are reserved for Microsoft’s internal use.

  • Row

    • IPv4 Primary subnet
    • This is a /30 subnet for your primary link. It can be a public or private IP address range, but it cannot be a range that is already being used in your Azure VNet.
  • Row

    • IPv4 Secondary subnet
    • This is another /30 subnet. It follows the same rules as the primary subnet, but is used with your secondary link.
  • Row

    • VLAN ID
    • This is the Private peering VLAN ID found on the PacketFabric BGP Settings page for the connection.
  • Row

    • Shared key
    • An optional MD5 hash. This must be present on both sides of the tunnel and is limited to 25 characters. Special characters are not supported.

For example:

screenshot of azure peering filled out

For more information, see the following Microsoft articles:

NOTE: At this time, Cloud Router does not support the Microsoft public peering option.

Add BGP information to the Cloud Router connection

  1. After completing the steps above, return to the Cloud Routers page in the PacketFabric portal.

  2. Click the Cloud Router to expand its connections.

  3. Click Configure BGP.

    Screenshot of the Configure button in the PacketFabric portal

Complete the following fields:

BGP Settings
  • Header row
    • Field
    • Description
  • Row 1
    • ASN
    • This is the Microsoft ExpressRoute ASN (12076) and cannot be edited.
  • Row 1
    • Primary peering VLAN ID
    • This is the VLAN ID assigned to the connection. You must provide this to Microsoft when configuring peering (see above). It cannot be edited.
  • Row 1
    • IPv4 primary subnet
    • Enter the same value you provided in the IPv4 Primary subnet field when configuring peering in the Azure portal (see above).
  • Row 1
    • IPv4 secondary subnet
    • Enter the same value you provided in the IPv4 Secondary subnet field when configuring peering in the Azure portal (see above).
  • Row 1
    • Shared key (Optional)
    • Enter the Shared key value you provided when configuring peering in the Azure portal (see above).
  • Row 1
    • Allow longer prefixes

    • This applies to the allowed incoming and outgoing prefixes that you list below.

      For example, say you list 172.16.2.0/24 as an allowed incoming prefix. You have three other cloud connections with the following outgoing prefixes:

      Connection A: 172.16.2.0/24
      Connection B: 172.16.0.0/16
      Connection C: 172.16.2.128/25

      If you do not select this option, only routes from Connection A are allowed.

      If you select this option, the routes from Connection A and Connection C are allowed.

NOTE ON SUBNETS:

PacketFabric programmatically selects one of the provided subnets to use.

The router peer IP addresses are automatically assigned from this subnet. The first usable IP is allocated to the PacketFabric Cloud Router, and the second is allocated to the Microsoft edge router.

For example, if you enter 192.168.100.128/30, the PacketFabric Cloud Router peer IP address is 192.168.100.129 and the Microsoft peer is 192.168.100.130.

NAT settings

This option appears if you selected a NAT-capable on-ramp.

Prefixes to NAT
The prefixes from the cloud that you want to associate with the NAT pool.
NAT Pool Prefixes
All prefixes that are NATed on this connection will be translated to the pool prefix address.
If this connection uses a public IP address, then this field is autofilled with the PacketFabric router prefix with /32.
If this connection uses a private IP address, then manually enter a /32 prefix that is different than the router peer IPs you entered above.
Allowed prefixes to cloud

This is a list of addresses that you want to allow into your Azure VNet. These can be addresses from other cloud environments or from a different Azure VNet.

If you are using NAT, this is pre-populated with the PacketFabric router peer IP.

  • Row
    • Field
    • Description
  • Row
    • ASN prepend

    • Number of additional times to add the ASN to the BGP path, resulting in a higher path length.

      Routes with higher path length (a higher ASN prepend value) have a lower priority.

  • Row
    • MED

    • The multi-exit discriminator (MED) value.

      When the same route is advertised in multiple locations, those with a lower MED are preferred by the peer AS.

  • Row
    • Prefix/Mask
    • Enter an allowed IP address range in CIDR format. You can add up to 1000 prefixes.
Allowed prefixes from cloud

This is a list of addresses from within the Azure environment that you want to advertise to other clouds. This can include the VPC internal space and any routes you have created.

  • Row
    • Field
    • Description
  • Row
    • Local preference
    • When the same route is received in multiple locations, those with a higher local preference value are preferred by the PacketFabric Cloud Router.
  • Row
    • Prefix/Mask
    • Enter an allowed IP address range in CIDR format. You can add up to 1000 prefixes.

Create a virtual network gateway for ExpressRoute

Before you continue, consider whether you want to utilize Azure’s zone-redundant gateways. For more information, see see High Availability and Redundancy in ExpressRoute Connections.

  1. Use the search bar at the top of the Azure portal to find and select Virtual network gateways.

    screenshot of azure portal search

  2. Click Add.

    screenshot of azure portal add action

  3. Under Basics, complete the following fields:

    • Header row
      • Field
      • Description
    • Row 1
      • Subscription
      • Select the subscription associated with your virtual network.
    • Row 2
      • Resource group
      • The resource group is autopopulated based on the virtual network you select.
    • Row 2
      • Name
      • Provide a meaningful name for the gateway.
    • Row 2
      • Region
      • Select the region associated with your virtual network.
    • Row 2
      • Gateway type
      • Select ExpressRoute.
    • Row 2
      • SKU

      • Select one of the following:

        • Standard/ErGw1AZ: 1,000 Megabits/second
        • High Performance/ErGw2AZ: 2,000 Megabits/second
        • Ultra Performance/ErGw3AZ: 10,000 Megabits/second

        The SKUs that begin with ErGw indicate that the gateway is in a zone-redundant region.

        If you are planning to implement FastPath, you must select the Ultra Performance gateway.

        For more information about the differences between SKUs, see Estimated performances by gateway SKU.

    • Row 2
      • Virtual network
      • Select the virtual network to which you are connecting.
    • Row 2
  4. Click Next to add tags (optional).

  5. Click Next and then Create.

IMPORTANT: Ensure you have already set up peering before linking your virtual network gateway. Otherwise, you will get an error when you provision the connection.
  1. In the Azure portal, go to the overview page for your ExpressRoute circuit.

  2. From the menu on the left, select Connections.

    screenshot of expressroute menu

  3. Click Add.

  4. Provide a meaningful name and then click Next.

  5. Under Settings, complete the following fields:

    • Header row
      • Field
      • Description
    • Row 1
      • Virtual network gateway
      • Select the gateway leading to the appropriate virtual network.
    • Row 2
    • Row 2
      • Routing weight

      • The routing weight is relevant when both of the following conditions are met:

        • A virtual network is connected to multiple circuits,

          AND

        • Those circuits are advertising the same network prefixes.

        In that situation, traffic is sent to the ExpressRoute circuit with the highest routing weight. You can enter a value between 0 and 32000.

  6. Click Next to add tags (optional).

  7. Click Next and then Create.