FAQ for the 'Iptables' Category
Viewing 21-30 of 30 FAQ -- Howto Secure portmap service using iptables and TCP Wrappers under Linux
Q. How do I secure the portmap service? I am using Debian Linux.
A. According to wikipedia, “Portmap is server software running under Unix-like systems that converts RPC program numbers into DARPA protocol port numbers. Its design objective was to minimize the number of ports in use, but this never happened as it never had wide [...] - Linux passive ftp not working problem and solution
Q. My passive ftp is not working, what can do to fix this problem?
A. Make sure firewall is not blocking your FTP session. If ports are open make sure IPtables is allowing passive ftp. To solve this problem add ip_conntrack_ftp module. Type the following command to load this module:
# modprobe ip_conntrack_ftp
Add this module [...] - Linux disable or remove the iptables firewall
Q. How do I disable the iptables firewall in Fedora Core Linux?
A. Iptables is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel.
If you are using RHEL (Redhat), Fedora core or Cent os just type following commands to disable the iptables firewall:
# service iptables save
# [...] - Linux Null route an attackers ip
Q. How do I null route an attakers IP under Red Hat Enterprise Linux? I would like to block unwanted traffic from a particular source.
A. A null route is a network route that goes nowhere. When a network packet is received by Linux (or UNIX or any other network device) operating system, it needs to [...] - Linux configure Network Address Translation or NAT
Q. How do I configure Linux as a router to perform Network Address Translation (NAT) using iptables? I am using Cent OS.
A. NAT, also known as network masquerading, native address translation or IP-masquerading involves re-writing the source and/or destination addresses of IP packets as they pass through a router or firewall. Most systems using NAT [...] - Iptables is not sending LOG to syslog file
Q. I am running SSH/MySQL/Webserver and setup iptables based firewall. But my logs are send to console rather than the system log files. How do make sure that iptables LOG target messages are send to /var/log/messages file?
A. IPTABLES LOG module turns on kernel logging of matching packets. When this option is set for a [...] - How do I save iptables rules or settings?
Q. I am using GUI tool to setup rules for my home computer connected to ADSL (DSL/Cable) network. However after reboot my rules are not there. Is there any way I can save and load them again.
A. You need to use iptables-save command which is used to dump the contents of an IP Table [...] - Iptables open ftp port 21
Use iptables administration tool for IPv4 packet filtering and NAT under Linux to open tcp port 21 (FTP). Following rule-set assumes that your eth0 network interface directly connected to internet. It has public ip (202.54.1.20). FTP use both port 21 and 20 (port 21 for the command port and port 20 for the data). So [...]
- How do I block an IP on my Linux server?
In order to block an IP on your Linux server you need to use iptables firewall. First you need to log into shell as root user. To block IP address you need to type iptables command as follows:
iptables -A INPUT -s IP-ADDRESS -j DROP
Replace IP-ADDRESS with actual IP address. For example if you wish to [...] - Restrict ssh access using Iptable
Q. How do I stop or restrict access to my OpenSSH (SSHD) server using Linux iptables based firewall?
A. Linux iptables firewall can be use to block or restrict access to ssh server. Iptables command is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. However, you [...]
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