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In this article, you learn how to add, modify, and remove advertised gateway prefixes on a hub virtual network. Advertised gateway prefixes let you specify summarized CIDR prefixes that Azure hybrid gateways advertise to on-premises networks instead of advertising all individual virtual network and spoke CIDRs.
For more information about this feature, see Advertised gateway prefixes overview.
Prerequisites
An Azure account with an active subscription. Create one.
A hub virtual network with a gateway subnet. See Create a virtual network.
An ExpressRoute gateway or VPN gateway deployed in the hub virtual network. See Create a VPN gateway or Create an ExpressRoute gateway.
One or more peered spoke virtual networks (to observe the summarization behavior).
Add advertised gateway prefixes
Use the following steps to add summarized gateway prefixes to your hub virtual network.
Sign in to the Azure portal.
In the search box at the top of the portal, enter Virtual networks. Select Virtual networks from the search results.
Select your hub virtual network (the virtual network containing your gateway subnet).
In Settings, select Address space.
In the Advertised gateway prefixes section, select + Add prefix.
Enter the summarized CIDR prefix that covers the address spaces you want to advertise. For example, enter 10.0.0.0/16 to summarize multiple /24 spoke networks.
To add more prefixes, repeat the previous step for each IPv4 or IPv6 CIDR prefix.
Select Save.
Note
For dual-stack (IPv4 + IPv6) virtual networks, add both IPv4 and IPv6 summarized prefixes explicitly.
Modify advertised gateway prefixes
Use the following steps to modify existing advertised gateway prefixes.
Sign in to the Azure portal.
In the search box at the top of the portal, enter Virtual networks. Select Virtual networks from the search results.
Select your hub virtual network.
In Settings, select Address space.
In the Advertised gateway prefixes section, modify the CIDR prefix values as needed.
Select Save.
Remove advertised gateway prefixes
Use the following steps to remove advertised gateway prefixes and revert to the default advertisement behavior.
Sign in to the Azure portal.
In the search box at the top of the portal, enter Virtual networks. Select Virtual networks from the search results.
Select your hub virtual network.
In Settings, select Address space.
In the Advertised gateway prefixes section, select the delete icon next to the prefix you want to remove.
Repeat for each prefix you want to remove.
Select Save.
Note
When all advertised gateway prefixes are removed, gateways revert to the default behavior of advertising all hub and peered spoke virtual network address spaces individually.
Verify configuration
Use the following steps to verify that your summarized prefixes are configured correctly.
Sign in to the Azure portal.
In the search box at the top of the portal, enter Virtual networks. Select Virtual networks from the search results.
Select your hub virtual network.
In Settings, select Address space.
Verify that the summarized prefixes appear in the Advertised gateway prefixes section.