Default network numbering

172.30.42.X range

CeroWrt is a test platform, and as such we wanted it to co-exist within existing networks as best as possible, without conflicting with an existing network, and to not require NAT in order to function inside that network. NAT skews some test results horribly.

Since there is no public IP address space left, 10.X.X.X networks are being increasingly used as backbone networks, and 192.168.X is most likely a number you are already using on your existing network, we chose the 172.16.0.0/12 range to play in. The default address for the router is 172.30.42.1.

It is ironic that this is the last piece of 'free' IP address space left. See also BANA.

If you find this IP hard to remember or type, DNS is enabled by default for a virtual subdomain of home.lan. You should be able to get to it via gw.home.lan if you get dhcp from the router and you can, of course, change this to a REAL subdomain of your own otherwise vanity web site name, if you want!

Changing the default ip address ranges is difficult to do via the web interface and we suggest you stick with it for a while until you understand the reasoning, firewall, routing, and naming rules. If you really must, read Changing_your_cerowrt_ip_addresses.

If you are running CeroWrt inside your network, and not as your default gw, configure your default gw to statically assign an ip address, and route your subnet to the CeroWrt router, and turn off NAT.

/27 subnet

The 'standard of 192.168.0.1' with a /24 netmask of 255.255.255.0 for a home network is obsolete. EVERY piece of gear comes up on that. Yes, it's simple, but:

  1. bridging together GigE (1000Mbit) with wireless (1Mbit for multicast) - doesn't work. One wired user can wipe out the entire wireless network with traffic. Once you concede this point... multiple networks are the only choice.
  2. Nobody has 255 machines on one network.
  3. CIDR has been a standard since 1992.
  4. We wanted to add more flexibility and security into a home or small business LAN
  5. A practical upper limit for wireless is about 30 devices per radio.

So we chose a different approach. Since /27 (255.255.255.224) netmasks result in 30 usable IP addresses, we broke the network into 8 equivalent pieces, laid out as follows:

IPv4 address Interface Description
Public IP ge00 Gateway Ethernet to Internet
1-30 se00 Secure Ethernet for wired devices
33-62 No interface
65-94 sw00 Secure Wireless (2.4 Ghz)
97-126 sw10 Secure Wireless (5.x Ghz)
129-158 gw00 Guest Wireless (2.4 Ghz)
161-190 gw10 Guest Wireless (5.x Ghz)
193-222 Mesh
225-254 DMZ

In practice you will hardly notice this setup on a new LAN, in fact, we expect overall performance to be 'smoother', especially if you migrate your newer devices to 5.x GHz and leave the 2.4GHz to legacy stuff like bluetooth and microwave ovens.

Integrating it with an existing LAN is a bit more difficult. Multicast (dns, service discovery, Windows filesharing, etc) is an issue - however it can be solved with regular DNS, a multicast responder, and a Samba WINS server. These are installed by default.

We want to make the integration problems easier to solve, out of the box, over time, and we hope you will see enormous performance benefits by leaving things split apart.

In the meantime, we'd love to know what current services don't work when split across multiple subnetworks like this.

See also

Default naming scheme
Changing IP, DNS, and SSID
Automated Configuration of CeroWrt