Configure BGP and BFD to accelerate route convergence - Express Connect

Scenario example

The following scenario is used as an example. An enterprise has a data center in Hangzhou and creates a VPC in the China (Hangzhou) region. The enterprise wants to use an Express Connect circuit to connect a customer-premises equipment (CPE) device to a VBR and use Cloud Enterprise Network (CEN) to enable communication between the data center and the VPC. To accelerate route convergence, the enterprise wants to configure BGP and BFD on the router in the data center and the VBR. This improves network availability.

Prerequisites

The data center is connected to Alibaba Cloud by using an Express Connect circuit. For more information, see Connect a data center to ECS by using an Express Connect circuit.
A BGP connection is established between the data center and the VPC. The BGP peer is in the Established state. For more information, see Configure BGP.

Step 1: Configure BFD on the VBR

Log on to the Express Connect console.
In the top navigation bar, select the region where you want to create a VBR. Then, in the left-side navigation pane, click Virtual Border Routers (VBRs).
On the Virtual Border Routers (VBRs) page, find the VBR whose configuration you want to modify and click Modify in the Actions column.
In the Edit VBR panel, configure the parameters and click OK.
In this example, Submission Interval is set to 1000 milliseconds, Reception Interval is set to 1000 milliseconds, and Detection Time Multiplier is set to 3. These are the default values.
Enable BFD
1. On the Virtual Border Routers (VBRs) page, find the VBR that you want to manage and click its ID.
2. On the BGP Peers tab, find the BGP peer that you want to manage and click Edit in the Actions column.
3. In the Modify BGP Peer panel, select Enable BFD, configure BFD Hop Count, and then click OK.
  BFD Hop Count specifies the maximum number of hops between the source and destination. You can specify this parameter based on the network topology. Valid values: 1 to 255.
  Important
  If you use BFD in a multi-cloud environment or a fiber-optic direct connection network without any bridge device, you need to change the default BFD hop count from 255 to 1.

Step 2: Configure BFD between the CE router and the VBR

Note

In this example, an H3C-6820 device is used. The configuration may vary based on devices. For more information, contact the service provider of your CPE device.

Log on to the CPE device and run the following command to configure BFD:
```
System-view
Bgp <Autonomous System Number (ASN) of the CPE device>
Peer <IP address of the VBR on the Alibaba Cloud side> bfd
```
Note
In this example, 10.101.1.2 is used as the IP address of the VBR.

To verify the BFD configurations, run the display bfd session verbose command.

The following information is returned. Session State: Up indicates that a BGP connection is established between the CPE device and the VBR and that BFD is enabled.

<CPE> display bfd session verbose
Total Session Num: 1 Up Session Num: 1 Init Mode: Active
IPv4 Session Working Under Ctrl Mode:
Local Discr: 513 Remote Discr: 513
Source IP: 10.101.1.1 Destination IP: 10.101.1.2
Session State: Up
Interface: N/A
Min Tx Inter: 500ms Act Tx Inter: 500ms
Min Rx Inter: 500ms Detect Inter: 2500ms
Rx Count: 135 Tx Count: 135
Connect Type: Indirect Running Up for: 00:00:58
Hold Time: 2457ms Auth mode: None
Detect Mode: Async Slot: 0
Protocol: BGP
Version:1
Diag Info: No Diagnostic

If multiple connections over Express Connect circuits are established between the data center and the VPC, repeat the preceding operations.

FAQ

Can I configure BFD on one VBR to accelerate route convergence when two VBRs are attached to a CEN instance?
Yes, you can configure BFD on one VBR to accelerate route convergence when two VBRs are attached to a CEN instance.
If BFD detects failures on one of two VBRs attached to a CEN instance, can the other VBR immediately take over?
Yes, the other VBR can immediately take over only if the two VBRs are added to a failover group. For more information, see Configure a failover group.