Merge pull request #32052 from TimLovellSmith/patch-2

Update required outbound IP connectivity for DNS on Port 53

Author: Jak-MS

articles/azure-cache-for-redis/cache-how-to-premium-vnet.md

@@ -109,14 +109,17 @@ There are seven outbound port requirements.
 | Port(s) | Direction | Transport Protocol | Purpose | Local IP | Remote IP |
 | --- | --- | --- | --- | --- | --- |
 | 80, 443 |Outbound |TCP |Redis dependencies on Azure Storage/PKI (Internet) | (Redis subnet) |* |
-| 53 |Outbound |TCP/UDP |Redis dependencies on DNS (Internet/VNet) | (Redis subnet) |* |
+| 53 |Outbound |TCP/UDP |Redis dependencies on DNS (Internet/VNet) | (Redis subnet) | 168.63.129.16 and 169.254.169.254 <sup>1</sup> and any custom DNS server for the subnet <sup>3</sup> |
 | 8443 |Outbound |TCP |Internal communications for Redis | (Redis subnet) | (Redis subnet) |
 | 10221-10231 |Outbound |TCP |Internal communications for Redis | (Redis subnet) | (Redis subnet) |
 | 20226 |Outbound |TCP |Internal communications for Redis | (Redis subnet) |(Redis subnet) |
 | 13000-13999 |Outbound |TCP |Internal communications for Redis | (Redis subnet) |(Redis subnet) |
 | 15000-15999 |Outbound |TCP |Internal communications for Redis | (Redis subnet) |(Redis subnet) |
 | 6379-6380 |Outbound |TCP |Internal communications for Redis | (Redis subnet) |(Redis subnet) |
 
+<sup>1</sup> These IP addresses owned by Microsoft are used to address the Host VM which serves Azure DNS.
+
+<sup>3</sup> Not needed for subnets with no custom DNS server, or newer redis caches that ignore custom DNS.
 
 #### Inbound port requirements