Transit Advanced Config


The advanced configuration applies to each Aviatrix Transit Gateway. Go to Multi-Cloud Transit -> Advanced Config -> Edit Transit. Select one gateway and apply the following changes.

Local AS Number

This option changes the Aviatrix Transit Gateway ASN number before you setup Aviatrix Transit Gateway connection configurations.

BGP Manual Advertised Network List

This field is only applicable to Transit GW established by Transit Network workflow.

By default, Aviatrix Transit GW advertises individual Spoke VPC CIDRs to VGW. You can override that by manually entering the intended CIDR list to advertise to VGW.

This feature is critical to limit the total number of routes carried by VGW (maximum is 100).

To enable this option in software version prior to 4.1, click Site2Cloud on the left navigation bar, select the connection established by Step 3, click to edit. Scroll down to “Manual BGP Advertised Network List” to enable.

For software version 4.1 and later, you will click Transit Network on the left navigation bar, click the Advanced Config option and browse to the Edit Gateway tab. Select the Transit Gateway you want to enable this feature on and scroll down to the “Manual BGP Advertised Network List” and enter the summarized CIDRs that you want to advertise

To disable the option, leave the field blank and click “Change BGP Manual Spoke Advertisement”.

Connection Manual BGP Advertised Network List

Manual Advertise Routes per BGP Connection expands the existing gateway based manual advertising routes feature to apply it to each BGP connection. One use case is to have better route advertising control for each remote BGP peer.

To enable this option on software version 6.3,

  • click “MULTI-CLOUD TRANSIT” on the left navigation bar, and then click the “Advanced Config” option
  • browse to the “Edit Transit” tab, and then select the Transit Gateway
  • find the panel “Connection Manual BGP Advertised Network List”, and then select the connection name and fill the CIDRs to advertise under field “Advertised Network List”

To disable the option, leave the field blank and click the button “CHANGE”.

Connected Transit

By default, Aviatrix Spoke VPCs do not have routing established to communicate with each other via Transit. They are completely segmented.

If you would like to build a full mesh network where Spoke VPCs communicate with each other via Transit GW, you can achieve that by enabling “Connected Transit” mode. All connections are encrypted.


For a Spoke VPC/VNet in a multi-cloud transit to communicate with a Spoke VPC in TGW Orchestrator, Connected

Transit must be enabled on the Aviatrix Transit Gateway that connects both sides.

For software version 4.1 and later, you will click Transit Network on the left navigation bar, click the Advanced Config option and browse to the Edit Gateway tab. Select the Transit Gateway you want to enable the Connected Transit.

Note all Spokes should be either in HA mode or non HA mode. A mixed deployment where some Spokes have HA enabled while others don’t work in a normal environment, but does not work when a failover happens on a HA enabled Spoke.


This option is to enable Equal Cost Multi Path (ECMP) routing for the next hop. For Aviatrix Transit Gateway next hop routing decision process, refer to ActiveMesh 2.0 next hop..

Click the Slide Bar to enable BGP ECMP.


This option is to provide the flexibility on Aviatrix Transit Gateways to connect to on-prem with only one active tunnel and the other one as backup. In addition, this Active-Standby Mode supports ActiveMesh 2.0 only.

The use case is a deployment scenario where on-prem device such as firewall does not support asymmetric routing on two tunnels. When Active-Standby mode is enabled, it applies to both BGP and Static Remote Route Based External Device Connections and for each connection, only one tunnel is active in forwarding traffic at any given time.

This feature can only be applied to non HA remote device in Multi-cloud transit Step 3.

Click the Slide Bar to enable Active-Standby mode.

Multi-Tier Transit

Use the Multi-Cloud Transit Gateway option to implement a hierarchical transit gateway architecture that permits packets to traverse more than 2 Aviatrix transit gateways. In previous releases, full-mesh transit peering was required. You can now connect the two CSPs or regions through one peered connection. You must use ActiveMesh 2.0 to use multi-tier transit gateways, but full-mesh transit peering is not required.


  • You can use Multi-Cloud Transit Gateway option with or without HPE.
  • Inter and intra-region peering are both supported.
  • Inter-CSP HPE over Internet is supported between AWS and Azure.
  • AWS TGW peering is not supported.

Gateway AS Path Prepend

You can insert BGP AS_PATH on the Aviatrix Transit Gateway to customize the BGP AP_PATH field when it advertises to VGW or peer devices. For example, enter 65458, 65478 in the input field, these ASN will appear to the remote end.

This configuration applies to all BGP peers of the Aviatrix Transit Gateway.

If you don’t configure this field, Transit Gateway only advertises its own ASN.

Connection AS Path Prepend

Customize AS Path Prepend by specifying AS PATH for each BGP connection. This feature applies to any dynamic connection and Transit Gateway peering connections on a selected Aviatrix Transit Gateway.

BGP Polling Time

Aviatrix Transit Gateways report its BGP routes to the Controller periodically. By default, the periodic timer is 50 seconds. This polling time affects BGP route change convergence time.

This option changes the default polling time. The range is 10 seconds to 50 seconds.

BGP Hold Time

Use the BGP Hold Time option to manually set the BGP holding time for your Aviatrix transit gateway. The hold time specifies how long a router waits for incoming BGP messages before it assumes the neighbor is dead.

The Aviatrix transit gateway hold time is bound to the Aviatrix keep alive message time which is always 1/3 of the hold time. By default, the Hold Time is 180 seconds and the Keep Alive time is 60 seconds. The supported Hold Time range is 12 to 180 seconds. If the remote site has a shorter hold time, the shorter hold time is used for the gateway.

Refresh BGP Advertised Routes

This option reset BGP connection to the remote BGP peers.

Use this option to enable new features such as “Segmentation based BGP CIDR Advertisements” where on-prem receives BGP advertisement for networks on-prem has connection policy or in the same Security Domain.

AWS TGW Edge Segmentation

Refer to TGW Edge Segmentation for details.

TGW Edge Segmentation can be enabled at given time. Select a connection to enable or disable.

BGP Overlapping Alert Email

When Aviatrix Controller detects overlapping network CIDRs in the network, it sends out alert emails to the admins.

BGP Route Limit Alert Email

AWS VGW BGP supports up to 100 routes. When this limit is reached, VGW BGP goes down and causes outage. This email alert notifies admin when routes approach 90.