Cisco APIC Getting Started Guide, Release 6.2(x)

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Change the external routable subnet

Updated: January 12, 2026

Overview

Learn how to modify the external routable subnet configuration in your network by following a step-by-step procedure to deactivate, delete, and reconfigure subnets using the Fabric Setup Policy panel, ensuring accurate IP address allocation and verification through APIC and spine switch CLI commands.

If you need to make changes to the information in subnets or TEP table after you've configured them, follow these steps to change the external routable subnet.

Note

You cannot change an external routable subnet configuration using multiple subnets.

Follow these steps to change the external routable subnet:

Procedure

1.

Navigate to the area where you originally configured the external routable subnet.

  1. On the menu bar, click Fabric > Inventory .

  2. In the Navigation pane, click Pod Fabric Setup Policy .

  3. On the Fabric Setup Policy panel, double-click the pod where you originally configured the external routable subnet.

    The Fabric Setup Policy for a POD page for this pod appears.

  4. Locate the information for the subnets or TEP table, depending on the release of your APIC software:

    • For releases prior to 4.2(3), locate the Routable Subnets table.

    • For 4.2(3) only, locate the External Subnets table.

    • For 4.2(4) and later, locate the External TEP table.
2.

Locate the external routable subnet that you want to delete in the table and determine if the state of that subnet is set to active or inactive .

If the state is set to active , change the state to inactive :

  1. Double-click on the entry in the subnets or TEP table for the existing external routable subnet that you want to delete.

  2. Change the state for the subnet to inactive , then click Update .
3.

Delete the existing external routable subnet.

  1. Click on the entry in the subnets or TEP table for the existing external routable subnet that you want to delete.

  2. Click the trashcan icon at the top of the table, then click Yes in the pop-up confirmation window to delete the external routable subnet.
4.

Wait for at least 30 seconds, then configure a new external routable subnet.

  1. Click + in the subnets or TEP table to configure a new external routable subnet.

  2. Enter the IP address and Reserve Address, if necessary, and set the state to active or inactive .

    • The IP address is the subnet prefix that you wish to configure as the routeable IP space.

    • The Reserve Address is a count of addresses within the subnet that must not be allocated dynamically to the spine switches and remote leaf switches. The count always begins with the first IP in the subnet and increments sequentially. If you wish to allocate the Unicast TEP from this pool, then it must be reserved.

  3. Click Update to add the new external routable subnet to the subnets or TEP table.

  4. On the Fabric Setup Policy panel, click Submit .
5.

Verify that the new routable IP address is configured correctly.

Log into the APIC controller through the CLI and enter the following command:


                  apic1# 
                  avread | grep routableAddress

Output similar to the following should appear:

routableAddress   14.3.0.228              14.3.0.229              14.3.1.228
6.

Check the NAT entries created on the spine switch.

Log into the spine switch through the CLI and enter the following command:


                  spine1# 
                  show nattable

Output similar to the following should appear:


                  -----NAT TABLE---------
                  Private Ip  Routable Ip
                  ----------  -----------
                  10.0.0.2    14.3.0.229 
                  10.0.0.1    14.3.0.228 
                  10.0.0.3    14.3.1.228