04-29-2008
Opening TCP ports
I'm not sure if this is the right place for this post, but I'd be grateful if somebody could please help me. I'm trying to open ports 999, 1982 and 1983 but am not having much luck. I used
iptables -A INPUT -i eth0 -p tcp --sport 999 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --sport 1982 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --sport 1983 -m state --state NEW,ESTABLISHED -j ACCEPT
to open the ports but haven't been successful. I was told to make sure that your server TCP ports: 999, 1982, 1983 are fully open inbound and outbound and that destination IP address for those ports is 72.232.181.106.
I've been trying for ages to get these ports open, but haven't had any luck.
This is the first time I've ever used a dedicated server and I am very new to all of this so I in advance for lack of knowledge
Thanks
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LEARN ABOUT FREEBSD
blackhole
BLACKHOLE(4) BSD Kernel Interfaces Manual BLACKHOLE(4)
NAME
blackhole -- a sysctl(8) MIB for manipulating behaviour in respect of refused TCP or UDP connection attempts
SYNOPSIS
sysctl net.inet.tcp.blackhole[=[0 | 1 | 2]]
sysctl net.inet.udp.blackhole[=[0 | 1]]
DESCRIPTION
The blackhole sysctl(8) MIB is used to control system behaviour when connection requests are received on TCP or UDP ports where there is no
socket listening.
Normal behaviour, when a TCP SYN segment is received on a port where there is no socket accepting connections, is for the system to return a
RST segment, and drop the connection. The connecting system will see this as a ``Connection refused''. By setting the TCP blackhole MIB to
a numeric value of one, the incoming SYN segment is merely dropped, and no RST is sent, making the system appear as a blackhole. By setting
the MIB value to two, any segment arriving on a closed port is dropped without returning a RST. This provides some degree of protection
against stealth port scans.
In the UDP instance, enabling blackhole behaviour turns off the sending of an ICMP port unreachable message in response to a UDP datagram
which arrives on a port where there is no socket listening. It must be noted that this behaviour will prevent remote systems from running
traceroute(8) to a system.
The blackhole behaviour is useful to slow down anyone who is port scanning a system, attempting to detect vulnerable services on a system.
It could potentially also slow down someone who is attempting a denial of service attack.
WARNING
The TCP and UDP blackhole features should not be regarded as a replacement for firewall solutions. Better security would consist of the
blackhole sysctl(8) MIB used in conjunction with one of the available firewall packages.
This mechanism is not a substitute for securing a system. It should be used together with other security mechanisms.
SEE ALSO
ip(4), tcp(4), udp(4), ipf(8), ipfw(8), pfctl(8), sysctl(8)
HISTORY
The TCP and UDP blackhole MIBs first appeared in FreeBSD 4.0.
AUTHORS
Geoffrey M. Rehmet
BSD
January 1, 2007 BSD