A lot more documentation.

docs/add_canned_isp.md

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+# `add_canned_isp` Command
+
+## Name
+
+`add_canned_isp`
+
+## Synopsis
+
+```
+add_canned_isp ${interface} ${custom_name} ${isp_name}
+```
+
+## Description
+
+Adds and configures an upstream ISP's connection interface.  This attempts to
+provision the connection as dual stack, both IPv4 and IPv6.  Interfaces that
+are external cannot also be internal.  ISP interfaces will be added to the
+`external` interface group, for ease of reference in `pf.conf` firewall rules.
+
+The specified `${interface}` will be provisioned for ISP uplink, according to
+the specified `${isp_name}` configuration rules.
+
+The `${custom_name}` parameter provides a user-defined name for a specific ISP
+link, which can be used with the `isp=...` options of [`add_net`](add_net.md) and
+related scripts.  It can be the same as `${isp_name}` but it does not have to be.
+
+The `${isp_name}` references ISP "hints" files in `${rc_router_dir}/hints` and
+`${rc_router_conf_dir}/hints`.  The latter of which can be populated with
+user-defined ISP hints.
+
+ISPs are always configured as `dhcp` for IPv4.  For custom static provisioning,
+other methods of provisioning these interfaces can be used.
+
+## See Also
+
+ - [`add_net`](add_net.md)
+ - [`add_vlan`](add_vlan.md)
+ - [`clone_interface`](clone_interface.md)