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CSS-Networking Update virtual-networks-udr-overview.md #127980

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6 changes: 5 additions & 1 deletion articles/virtual-network/virtual-networks-udr-overview.md
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Expand Up @@ -34,6 +34,10 @@ Each route includes an address prefix and next hop type. Azure uses the route wi
|Default|172.16.0.0/12 |None |
|Default|192.168.0.0/16 |None |
|Default|100.64.0.0/10 |None |
|Default|157.59.0.0/16 |None |
|Default|127.0.0.0/8 |None |
|Default|104.147.0.0/16 |None |
|Default|104.146.0.0/17 |None |

The next hop types listed in the previous table represent how Azure routes traffic destined for the address prefix listed. Here are explanations for the next hop types:

Expand All @@ -44,7 +48,7 @@ The next hop types listed in the previous table represent how Azure routes traff
* **10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16**: Reserved for private use in RFC 1918.
* **100.64.0.0/10**: Reserved in RFC 6598.

If you assign any of the previous address ranges within the address space of a virtual network, Azure automatically changes the next hop type for the route from **None** to **Virtual network**. If you assign an address range to the address space of a virtual network that includes, but isn't the same as, one of the four reserved address prefixes, Azure removes the route for the prefix and adds a route for the address prefix you added, with **Virtual network** as the next hop type.
If you assign any of the previous address ranges within the address space of a virtual network, Azure automatically changes the next hop type for the route from **None** to **Virtual network**. If you assign an address range to the address space of a virtual network that includes, but isn't the same as, one of the four reserved address prefixes, Azure removes the route for the prefix and adds a route for the address prefix you added, with **Virtual network** as the next hop type. Default Route (0.0.0.0/0) with Next Hop Type = Virtual Network Gateway will cause these Default System Routes with Next Hop Type = None to be removed. 
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Copilot AI Dec 4, 2025

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The reference to 'four reserved address prefixes' is now inaccurate since eight default routes with next hop type 'None' are now documented (the original four RFC ranges plus the four newly added routes). This reference should be updated to accurately reflect the total number of reserved address prefixes or be rephrased to avoid a specific count.

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If you assign any of the previous address ranges within the address space of a virtual network, Azure automatically changes the next hop type for the route from **None** to **Virtual network**. If you assign an address range to the address space of a virtual network that includes, but isn't the same as, one of the four reserved address prefixes, Azure removes the route for the prefix and adds a route for the address prefix you added, with **Virtual network** as the next hop type. Default Route (0.0.0.0/0) with Next Hop Type = Virtual Network Gateway will cause these Default System Routes with Next Hop Type = None to be removed. 
If you assign any of the previous address ranges within the address space of a virtual network, Azure automatically changes the next hop type for the route from **None** to **Virtual network**. If you assign an address range to the address space of a virtual network that includes, but isn't the same as, one of the reserved address prefixes listed above, Azure removes the route for the prefix and adds a route for the address prefix you added, with **Virtual network** as the next hop type. Default Route (0.0.0.0/0) with Next Hop Type = Virtual Network Gateway will cause these Default System Routes with Next Hop Type = None to be removed. 

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### Optional default routes

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