Categories Archives: Networking

PHP IPv4 and IPv6 Network and Subnet Calculator

Just threw together a quick and dirty PHP-based subnet calculator. What sets this one apart from others is that it works with both IPv4 and IPv6 inputs and has subnet splitting capability. Use the first field to enter a network to get details about. The format is CIDR notation ‘1.2.3.4/22’. Use the second field to […]

Adding alias IP subnet to an interface or VLAN

In the PFsense docs it tells you to use the ‘alias’ option in the web interface… but this won’t work for routed (non-NAT) interfaces that require more than 1 subnet attached to them. To overcome this, I utilized this article: http://doc.pfsense.org/multiple-subnets-one-interface-pfsense.pdf In summary: Log into the webGUI, and click Diagnostics -> Backup/Restore. Click the “Download […]

hostapd init script for Redhat/CentOS

Hostapd is a software daemon that turns a Linux box into a full blown wireless access point, but it doesn’t come with an init script to automatically start it when the machine boots up. It seems each Linux distribution that supports hostapd does their own thing, so I went ahead and created this little init […]

Sysctl and ip_conntrack_max optimization

On a busy webserver, you have to be very careful that you don’t run out of connection tracking buckets. Check how many you have set as your max: /sbin/sysctl net.ipv4.ip_conntrack_max Check how many you’re using: wc -l /proc/net/ip_conntrack A good maximum setting for most web servers with at least 2Gb RAM is 65536. Change the […]