Yesterday I got a new computer as my homeserver, a HP Proliant Microserver. Installed Arch Linux on it, with kernel version 3.2.12.

After installing iptables (1.4.12.2 - the current version afaik) and changing the net.ipv4.ip_forward key to 1, and enabling forwarding in the iptables configuration file (and rebooting), the system cannot use any of its network itnerfaces. Ping fails with

    Ping: sendmsg: operation not permitted

If I remove iptables completely, networking is okay, but I need to share the Internet connection to the local network.

eth0 - wan NIC integrated on the motherboard (no idea of vendor, probably HP). eth1 - lan NIC in a pci-express slot (Intel Gigabit CT Desktop http://www.intel.com/content/www/us/en/network-adapters/gigabit-network-adapters/gigabit-ct-desktop-adapter.html)

Since it works without iptables(server can access the internet, and I can login with ssh from the internal network), I assume it has something to do with iptables. I do not have much experience with iptables, so I used these as reference (separate from each other of course...):

wiki.archlinux.org/index.php/Simple_stateful_firewall#Setting_up_a_NAT_gateway

revsys.com/writings/quicktips/nat.html

howtoforge.com/nat_iptables

On my previous server, I used the revsys guide to set up nat, worked like a charm.

Anyone experienced anything like this before? What am I doing wrong?

Thanks, estol