SCCo ARES/RACES Intranet Addressing

SCCo ARES/RACES Network Addresses

The following network address ranges are reserved for the SCCo ARES/RACES Data Network. If you are using private IP address space within your local network, be sure to use addresses other than the ones below.

SCCo ARES/RACES Core Network

10.240.0.0/12 (mask 255.240.0.0) (10.240.0.0 through 10.255.255.255): Used for the SCCo ARES/RACES core network, including the servers that you will use (packet, email, DNS, etc.). The SCCo ARES/RACES network team has management control of all devices in this range.
44.4.50.0/26 (mask 255.255.255.192) (44.4.50.0 through 44.4.50.63): Used for SCCo AMPRnet connectivity. The SCCo ARES/RACES network team has management control of all devices in this range.

Access and Subscriber Networks

10.232.0.0/13 (mask 255.248.0.0) (10.232.0.0 through 10.239.255.255): Used for handoff networks between the SCCo ARES/RACES network and subscribers. Subscribers have management control of devices in this range. You can easily identify other SCCo ARES/RACES network subscribers (such as users from other cities) by these source addresses. This lets you configure your firewall to either allow or deny users from other subscriber sites from accessing servers on your network.

Subscriber Networks

Each subscriber will have exclusive use of a /24 IP address space (254 addresses, mask 255.255.255.0) from the “Access and Subcriber Networks” range of addresses listed above. For purposes of this documentation, we’ll refer to the address space as a.b.c.0/24 (network a.b.c.0, mask 255.255.255.0).

Within the subscriber’s address space, the last /28 subnet, a.b.c.240/28 (mask 255.255.255.240), will be used for a handoff subnet. The address assignments are as follows:

a.b.c.240: Network number (no hosts allowed)
a.b.c.241: Subscriber’s gateway/firewall
a.b.c.242–247: Subscriber hosts — statically assigned addresses
a.b.c.248–251: Subscriber hosts — dynamically assigned by DHCP
a.b.c.252–253: Reserved for SCCo ARES/RACES testing/diagnostics
a.b.c.254: SCCo ARES/RACES gateway
a.b.c.255: Broadcast address (no hosts allowed)

This arrangement has several advantages:

Consistent addressing for gateways. When a disaster strikes and documentation is hard to reach, consistent, simple rules are easier to follow.
Six static addresses for appliances, servers, or source/destination NATing
Four dynamically assigned addresses makes it easy to hook up a few devices for initial connectivity or testing/diagnostics
Although inadvisable for security reasions, the six static addresses and four dynamic addresses can be used for simple configurations where the subscriber has no other firewall or networks to attach.

The remaining 239 addresses (a.b.c.1–239) in the /24 address space are available for use by the subscriber for further subnetting.

The SCCo ARES/RACES network will drop all inbound traffic from subscribers if the source address is not within the subscriber’s assigned address space. This is commonly called “network ingress filtering” and is used to prevent IP address spoofing. It is documented in RFC 2827, BCP 38. This means that subscribers with larger networks that use addresses other than their assigned /24 address space will need to NAT (Network Address Translation) their other addresses into one or more addresses in their assigned /24 address range. The /24 address space provides plenty of space for NATing.

Subscriber Host Configuration

Subscribers are strongly encouraged to install their own firewall between their network and the SCCo ARES/RACES network. While we endevour to maintain high security within the SCCo ARES/RACES network, configuration mistakes and software bugs can occur. And new types of threats will always emerge in the future. Subcribers should take charge of their own security by installing and managing their own firewall.

That said, subscribers that choose to place hosts directly on the handoff subnet can either configure them statically or use DHCP provided by the SCCo ARES/RACES gateway.

Static Configuration

IP Address: Choose a unique address in the a.b.c.242–247 range.
Network Mask: 255.255.255.240
Default Gateway (if no other network attached): Destination: 0.0.0.0/0
Next Hop Gateway: a.b.c.254
Metric: 1
DNS Servers: As specified by SCCo ARES/RACES network team

DHCP Configuration

IP Address: Automatically assigned in the a.b.c.248–251 range.
Network Mask: Automatically assigned to 255.255.255.240.
Default Gateway: Automatically assigned to a.b.c.254.
DNS Servers: Automatically assigned