# `add_net` Command

## Name

`add_net`

## Synopsis

```
add_net ${card} ${vlan} ${group} [{no_ula|isp=abc|no_isp}...]
```

## Description

Adds an internal network segment with the specified vlan on the specified
card.  The created vlan-adaptor is put into the specified group.  It is setup
for both IPv4 and (where the ISP provides for it) IPv6.

If `${vlan}` is 0, then no tagged VLAN interfaces will be created; however,
the subnet address computations will still be performed as-if the vlan
were created.  This means that `xy0` will use `0` or `00` for its subnet
computations in IPv4 and IPv6 respectively.  If you don't intend to use
VLANs for subnets, just use VLAN ID 0 when declaring networks.

The IPv4 network will be a `/24` under `${v4_net_xy0}` if `${card}` is
`xy0`, for example.  If `${v4_net_xy0}` is not set, then `${v4_net}` is
used by default.  The 3rd octet will be `$(( ${vlan}/10 + ${vlan}%10 ))`.  For
example, if `${vlan}` is `102` and `${v4_net}` is `172.18`, then the configured
v4 network will be `172.18.12.0/24` and the router will hold address
`172.18.12.1`.  By default, IPv4 network DHCP configuration is enabled and
the range `.100` to `.200` will be used as a dynamic allocation pool.

The IPv6 network will make `$(( ${vlan}/10 + ${vlan}%10 ))` into hex digits
to be appended to the ISP's IPv6 prefix.  This makes it compatible with the
most common case of `/56` for most ISPs.  If `no_ula` is specified in the
optional arguments, then a ULA for this network segment will not be created.
Otherwise, the `${rc_router_network_name}` variable will be hashed and an
ISP-like prefix of `/48` will be created to which the SLA for the specified
network will be appended.  The `${rc_router_ula_prefix_size}` can be set to
`56` to specify a ULA prefix length of 56.  (No other lengths are supported
at this time.)

The `isp=...` flag can be used to assign the specified subnet to be part
of the `IA_PD` list for the specified ISP.  The `no_isp` flag can be used to
skip provisioning the specified network with any ISP's DHCPv6 `IA_PD` request.

This calls [`add_v4_net`](add_v4_net.md) and [`add_v6_net`](add_v6_net.md) and
passes all of its arguments.

## Subnet Calculation

(It is strongly recommended that the 10s digit and 1000s digit of the VLAN ID be
kept as `0`, as those digits are reserved for future improvements.  While this
limits the system to 100 vlans, it provides 1:1 visual alignment between IPv4,
IPv6, and VLAN ID.  Each can be visually compared to the others.)

|VLAN|IPv4 (3rd octet)|IPv6 suffix (hex)|Example IPv4   |Example IPv6           |
|---:|---------------:|----------------:|--------------:|----------------------:|
|   0| 0              |  0              |192.168.0.0/24 |2001:db8:abcd:ef00::/64|
|   7| 7              |  7              |192.168.7.0/24 |2001:db8:abcd:ef07::/64|
| 101|11              | 11              |192.168.11.0/24|2001:db8:abcd:ef11::/64|
| 205|25              | 25              |192.168.25.0/24|2001:db8:abcd:ef25::/64|
| 900|90              | 90              |192.168.90.0/24|2001:db8:abcd:ef90::/64|

## Options

 - `no_ula` - Do not create a Unique Local Address for this network (on the IPv6
   side).
 - `isp=${NAME}` - Attach this network to a specified ISP's configuration
 - `no_isp` - This network should not be associated with any ISP (declines to
   add network to DHCPv6 PD, among other things).

## Examples

#### Basic home LAN
`add_net abc2 100 main`

#### Guest network with no ULA
`add_net xy2 102 guest no_ula`

#### IoT network with no ULA and no ISP prefix delegation
`add_net xy2 103 iot no_ula no_isp`

#### Management network on a different ISP PD
`add_net xy2 402 mgmt isp=fios_1`

## See Also

 - [`add_v4_net`](add_v4_net.md)
 - [`add_v6_net`](add_v6_net.md)
 - [`add_vlan`](add_vlan.md)
 - [`add_rtadv`](add_rtadv.md)