Update docs for forwarding rule ip address (#4082)

Signed-off-by: Modular Magician <[email protected]>

website/docs/r/compute_forwarding_rule.html.markdown

@@ -142,16 +142,14 @@ The following arguments are supported:
   forwarding rule. By default, if this field is empty, an ephemeral
   internal IP address will be automatically allocated from the IP range
   of the subnet or network configured for this forwarding rule.
-  An address can be specified either by a literal IP address or a URL
-  reference to an existing Address resource. The following examples are
-  all valid:
-  * 100.1.2.3
-  * https://www.googleapis.com/compute/v1/projects/project/regions/
-       region/addresses/address
-  * projects/project/regions/region/addresses/address
-  * regions/region/addresses/address
-  * global/addresses/address
-  * address
+  ~> **NOTE** The address should be specified as a literal IP address,
+  e.g. `100.1.2.3` to avoid a permanent diff, as the server returns the
+  IP address regardless of the input value.
+  The server accepts a literal IP address or a URL reference to an existing
+  Address resource. The following examples are all valid but only the first
+  will prevent a permadiff. If you are using `google_compute_address` or
+  similar, interpolate using `.address` instead of `.self_link` or similar
+  to prevent a diff on re-apply.
 
 * `ip_protocol` -
   (Optional)

website/docs/r/compute_global_forwarding_rule.html.markdown

@@ -233,24 +233,27 @@ The following arguments are supported:
   (Optional)
   The IP address that this forwarding rule is serving on behalf of.
   Addresses are restricted based on the forwarding rule's load balancing
-  scheme (external or internal) and scope (global or regional).
-  The address must be a global IP for external global forwarding rules.
-  If this field is empty, an ephemeral IPv4 address from the same scope
-  (global) is closen. Global forwarding rules supports either IPv4 or IPv6.
-  When the load balancing scheme is INTERNAL_SELF_MANAGED, this must be
-  a URL reference to an existing Address resource (internal regional
-  static IP address), with a purpose of GCE_END_POINT and addressType
-  of INTERNAL.
-  An address can be specified either by a literal IP address or a URL
-  reference to an existing Address resource. The following examples are
-  all valid:
-  * 100.1.2.3
-  * https://www.googleapis.com/compute/v1/projects/project/regions/
-       region/addresses/address
-  * projects/project/regions/region/addresses/address
-  * regions/region/addresses/address
-  * global/addresses/address
-  * address
+  scheme (EXTERNAL or INTERNAL) and scope (global or regional).
+  When the load balancing scheme is EXTERNAL, for global forwarding
+  rules, the address must be a global IP, and for regional forwarding
+  rules, the address must live in the same region as the forwarding
+  rule. If this field is empty, an ephemeral IPv4 address from the same
+  scope (global or regional) will be assigned. A regional forwarding
+  rule supports IPv4 only. A global forwarding rule supports either IPv4
+  or IPv6.
+  When the load balancing scheme is INTERNAL, this can only be an RFC
+  1918 IP address belonging to the network/subnet configured for the
+  forwarding rule. By default, if this field is empty, an ephemeral
+  internal IP address will be automatically allocated from the IP range
+  of the subnet or network configured for this forwarding rule.
+  ~> **NOTE** The address should be specified as a literal IP address,
+  e.g. `100.1.2.3` to avoid a permanent diff, as the server returns the
+  IP address regardless of the input value.
+  The server accepts a literal IP address or a URL reference to an existing
+  Address resource. The following examples are all valid but only the first
+  will prevent a permadiff. If you are using `google_compute_address` or
+  similar, interpolate using `.address` instead of `.self_link` or similar
+  to prevent a diff on re-apply.
 
 * `ip_protocol` -
   (Optional)