Tuesday, December 16, 2008

My network layout

For those interested, this is how I lay out my network.

The center of the network is the gateway/router box. It's got three network interfaces on it. eth0 connects to the wired LAN, network Off the gateway is an 8-port switch that handles the computer room, with a run out to the living room and a 5-port switch for the game console and my laptop when I'm out on the couch or I've run a cable outside to sit on the walkway. It's all 100-megabit Ethernet, I'm planning on upgrading to gigabit at some point. Outgoing connections/flows from this network are relatively unrestricted. The only blocks are for DNS, it's only permitted to the gateway box.

eth1 on the gateway connects to a 5-port switch where the wireless access points are attached on network This network is considered untrusted, forwarding from it to other networks isn't permitted at the router so machines on it can only talk to each other or the router. In addition the router blocks incoming traffic on that interface except for DHCP and IPSec. This limits what a rogue machine on that network can do. The access points don't have WEP/WPA enabled, but they do do MAC filtering. When I upgrade to a faster AP I may enable WPA using authentication just to annoy the kiddies. The primary use for this network is to carry the IPSec VPN traffic on the network. This network is considered trusted, and has the same outbound restrictions as the wired LAN segment. Forwarding between the wired LAN and VPN segments is unrestricted and un-NATed.

eth2 on the gateway is connected to the cable modem and gets it's address via DHCP from Cox. Traffic from the wired LAN and VPN going out this interface is NATed. Incoming new connections are generally blocked, with specific holes opened for connection to services on the gateway machine (ssh, Apache on a high port, the DHCP client). The outside world is considered untrusted. Outgoing traffic has a few restrictions to prevent un-NATed addresses from escaping.

Most security is based on limited physical access to the hard-wired network. The wireless network that can be reached from outside the apartment is treated the same as any network I don't control. Laptops on it should be firewalled as if operating on a hostile network, and use IPSec to make a VPN connection to the rest of my network. This avoids my having to rely on hardware I don't completely control for security.

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