Im preparing to deploy about a thousand fanless machines running Debian. Each machine has 3 interfaces (eth0, eth1 and uap0). In many cases these machines will sit between a cable modem and a home router / network so I need to be transparent between eth0 and eth1. To this end I have setup dnsmasq in hopes of routing traffic and providing addresses.
DNSMASQ.CONF file is fairly simple. Mostly all I've added were the lines:
In hopes of securing the machine I'm trying to lock down any ports available on eth0. Using
nmap -v -p1-65535 <hostname> I see that ports 22, 53, 80 and 111 are answering on eth0. 22 and 80 I understand (ssh and httpd). What concerns me is port 53.
lsof -i :53 shows that dnsmasq is answering there.
Why? Do I need to add iptables entries to block this? Will it still work if I do this?