Cisco Catalyst SD-WAN Control Components and Device Management Guide, Releases 26.x and Later

PDF

Configuring automatic bandwidth detection

Updated: June 9, 2026

Want to summarize with AI?

Describes methods for configuring automatic bandwidth detection.

Configure automatic bandwidth detection using templates

Configure automatic bandwidth detection using templates.

Also see Configure automatic bandwidth detection using CLI commands.

You can configure the Cisco VPN Interface Ethernet template to cause a device to automatically detect the bandwidth for WAN interfaces in VPN0 during its day 0 onboarding. If you configure a template in this way, a Cisco IOS XE Catalyst SD-WAN device attempts to determine the bandwidth for WAN interfaces in VPN0 after completing the PnP process.

Automated bandwidth detection can provide more accurate day 0 bandwidth configuration than manual configuration because there is limited user traffic that can affect results.

A device determines the bandwidth by performing a speed test using an iPerf3 server. iPerf3 is a third-party tool that provides active measurements of bandwidth on IP networks. For more information, see the Iperf.fr website.

If a device has a connection to the internet, the device uses a public iPerf3 server for automatic bandwidth detection, unless you specify a private iPerf3 server. If a device has a connection to a private circuit and no internet connection, you must specify a private iPerf3 server for automatic bandwidth detection.

We recommend that you specify a private iPerf3 server. If a private iPerf3 server is not specified, the device pings a system defined set of public iPerf3 servers and selects for the speed test the public server with the minimum hops value or, if all servers have the same minimum hops value, the server with the minimum latency value. If the speed test fails, the device selects another public server from the list. The device continues to select other public iPerf3 servers until the speed test is successful or until it has tried all servers. Therefore, a speed test on a public iPerf3 server can use a server that is far away, resulting in a larger latency than the minimum.

The set of system defined public iPerf3 servers includes:

iperf.scottlinux.com
iperf.he.net
bouygues.iperf.fr
ping.online.net
iperf.biznetnetworks.com

Before you begin

Configure automatic bandwidth detection.

Procedure

From the Cisco SD-WAN Manager menu, choose Configuration > Templates.

Create a new Cisco VPN Interface Ethernet feature template or edit an existing one.

To create a new Cisco VPN Interface Ethernet feature template, click Feature Templates, click Add Template, select a device type, and select the Cisco VPN Interface Ethernet template.
To update an existing Cisco VPN Interface Ethernet feature template, click Feature Templates, click ... adjacent to a template, and select Edit.

For a new template, enter a name and description.

Configure bandwidth detection.


Field	Description
Auto Detect Bandwidth	When enabled, the device detects the bandwidth.
Iperf Server	To use a private iPerf3 server for automatic bandwidth detection, enter the IPv4 address of the private server. To use a public iPerf3 server for automatic bandwidth detection, leave this field blank. The private iPerf3 server should run on port 5201, which is the default iPerf3 port.

Ensure that the allow-service all command is configured for the tunnel interface.

The device writes the results of a speed test to the auto_speedtest.json file in its bootflash directory. It also displays the results in the Auto Upstream Bandwidth (bps) and Auto Downstream Bandwidth (Mbps) areas on the Monitor > Devices > Interface page of Cisco SD-WAN Manager.

If a device does not receive a response from an iPerf3 server, an error is recorded in the auto_speedtest.json file and displays on the Monitor > Devices > Interface page of Cisco SD-WAN Manager.

Configure automatic bandwidth detection using CLI commands

Configure automatic bandwidth detection using CLI commands.

Also see Configure automatic bandwidth detection using templates.

To disable auto-bandwidth-detect, use the no form of the command: no auto-bandwidth-detect .

Before you begin

Perform these steps to configure automatic bandwidth detection.

Procedure

	1.	Create a CLI add-on profile or CLI add-on template.
	2.	Use the auto-bandwidth-detect command to enable automatic bandwidth detection. `auto-bandwidth-detect iperf-server ipv4-address`
	3.	Ensure that the allow-service all command is configured for the tunnel interface.

The example includes the auto-bandwidth-detect , iperf-server , and allow-service all commands.

sdwan
 interface GigabitEthernet0/0/0
  tunnel-interface
   encapsulation gre
   allow-service all
   no allow-service bgp
   allow-service dhcp
   allow-service dns
   allow-service icmp
   allow-service sshd
   allow-service netconf
   no allow-service ntp
   no allow-service ospf
   no allow-service stun
   allow-service https
   no allow-service snmp
   no allow-service bfd
  exit
  auto-bandwidth-detect
  iperf-server 192.0.2.255
 exit
 appqoe
  no tcpopt enable
  no dreopt enable

Need help?

Open a support case

(Requires a Cisco Service Contract)

The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.