Sponsored Content
Top Forums UNIX for Dummies Questions & Answers iptables to block port 25 only to a certain range Post 302897064 by holyearth on Thursday 10th of April 2014 05:30:39 PM
Old 04-10-2014
iptables to block port 25 only to a certain range

I want to limit all *outbound* traffic on eth0 (or all *.*) on port 25 to a specific (allowed) range...

I.E.
192.168.1.5 (local ip) tries to connect to 1.2.3.4:25 (outside real world ip)

It can proceed because 1.2.3.0/24 is the allowed range

Now, 192.168.1.5 (local ip) tries to connect to 2.3.4.5:25 it is not allowed (drop?) because 2.3.4.5 is not part of the 1.2.3.0/24

Thanks for the help I could not find a way to do this:

This did not work:
iptables -A OUTPUT -o eth0 -p tcp -d 1.2.3.0/24 --dport 25 -m state --state NEW,ESTABLISHED -j ACCEPT


Thanks!
 

10 More Discussions You Might Find Interesting

1. IP Networking

How to know port is block..

My server is running on a port 16386, in the case when this port is blocked by some other application ( anti virus etc. ) or firewall then how do i know it's block? Is bind will return any specific error in this case. I have to know is it blocked or not? (2 Replies)
Discussion started by: Saurabh78
2 Replies

2. IP Networking

How to block a port

Hi, i faced a problem, where i have to block a port, therefore nobody used it, evenwith SO_REUSEADDR flag. How can i achive it. (4 Replies)
Discussion started by: Saurabh78
4 Replies

3. AIX

TCP/UDP port range for default AIX NFS?

May I know what is the TCP/UCP port range for any default AIX NFS? Based on rpcinfo -p, I got the following output: program vers proto port service 100000 4 udp 111 portmapper 100000 3 udp 111 portmapper 100000 2 udp 111 portmapper 100000 4 ... (4 Replies)
Discussion started by: famasutika
4 Replies

4. UNIX for Advanced & Expert Users

Ip And Port Divertion Through Iptables

Hi To All, I want to Route my web application to Mysql Database through a proxy server.so for this which approach should i use 1)iptables 2)squid if Iptables how can i make this worked .this is the ip network i'm having web application---------Proxy server-----------------Mysql Database... (0 Replies)
Discussion started by: kgrvamsi
0 Replies

5. Shell Programming and Scripting

Block local and remote port with iptables - Script BASH

Hello I'm beginner in the linux scripting and i would like to get help. I want to create a script that can block one or more Port even see all the TCP port. The ports must be blocked even when starting my machine. Of course requires a second script which will allow the ports that you want to... (0 Replies)
Discussion started by: houstaf
0 Replies

6. AIX

Allow port range using IPsec?

Hi Guys, Please could you tell me if it is possible to have a single rule/filter to allow a certain port range instead of a separate rule for each port? I'm sure it must be possible but I am unable to find the syntax. Thanks Chris (4 Replies)
Discussion started by: chrisstevens
4 Replies

7. Red Hat

Which is the effective ephemeral port range in Linux 2.6 for this set up?

In my Linux system ephemeral port range is showing different ranges as follows $ cat /proc/sys/net/ipv4/ip_local_port_range 32768 61000  cat /etc/sysctl.conf | grep net.ipv4.ip_local_port_range net.ipv4.ip_local_port_range = 9000 65500 Which will be the effective ephemeral port... (5 Replies)
Discussion started by: steephen
5 Replies

8. Red Hat

iptables help for port 80

Hi I enable the IPtables but port 80 was not working. Below is my active configuration (10 Replies)
Discussion started by: ranjancom2000
10 Replies

9. AIX

Forcing named 9 to use a fixed ephemeral port range

I'll start with I'm not an AIX expert, I inherited a lot of AIX servers to maintain. My problem is on AIX 7.1 TL4 SP4 environments. I'm running named as a DNS forwarder only to internal DNS servers. These AIX servers have a customized UDP ephemeral port range to avoid conflicting with the... (0 Replies)
Discussion started by: seanc
0 Replies

10. UNIX for Beginners Questions & Answers

Bash script, find the next closed (not in use) port from some port range.

hi, i would like to create a bash script that check which port in my Linux server are closed (not in use) from a specific range, port range (3000-3010). the print output need to be only 1 port, and it will be nice if the output will be saved as a variable or in same file. my code is: ... (2 Replies)
Discussion started by: yossi
2 Replies
PPTPD.CONF(5)							File Formats Manual						     PPTPD.CONF(5)

NAME
pptpd.conf - PPTP VPN daemon configuration DESCRIPTION
pptpd(8) reads options from this file, usually /etc/pptpd.conf. Most options can be overridden by the command line. The local and remote IP addresses for clients must come from the configuration file or from pppd(8) configuration files. OPTIONS
option option-file the name of an option file to be passed to pppd(8) in place of the default /etc/ppp/options so that PPTP specific options can be given. Equivalent to the command line --option option. stimeout seconds number of seconds to wait for a PPTP packet before forking the pptpctrl(8) program to handle the client. The default is 10 seconds. This is a denial of service protection feature. Equivalent to the command line --stimeout option. debug turns on debugging mode, sending debugging information to syslog(3). Has no effect on pppd(8) debugging. Equivalent to the command line --debug option. bcrelay internal-interface turns on broadcast relay mode, sending all broadcasts received on the server's internal interface to the clients. Equivalent to the command line --bcrelay option. connections n limits the number of client connections that may be accepted. If pptpd is allocating IP addresses (e.g. delegate is not used) then the number of connections is also limited by the remoteip option. The default is 100. delegate delegates the allocation of client IP addresses to pppd(8). Without this option, which is the default, pptpd manages the list of IP addresses for clients and passes the next free address to pppd. With this option, pptpd does not pass an address, and so pppd may use radius or chap-secrets to allocate an address. localip ip-specification one or many IP addresses to be used at the local end of the tunnelled PPP links between the server and the client. If one address only is given, this address is used for all clients. Otherwise, one address per client must be given, and if there are no free addresses then any new clients will be refused. localip will be ignored if the delegate option is used. remoteip ip-specification a list of IP addresses to assign to remote PPTP clients. Each connected client must have a different address, so there must be at least as many addresses as you have simultaneous clients, and preferably some spare, since you cannot change this list without restarting pptpd. A warning will be sent to syslog(3) when the IP address pool is exhausted. remoteip will be ignored if the dele- gate option is used. noipparam by default, the original client IP address is given to ip-up scripts using the pppd(8) option ipparam. The noipparam option pre- vents this. Equivalent to the command line --noipparam option. listen ip-address the local interface IP address to listen on for incoming PPTP connections (TCP port 1723). Equivalent to the command line --listen option. pidfile pid-file specifies an alternate location to store the process ID file (default /var/run/pptpd.pid). Equivalent to the command line --pidfile option. speed speed specifies a speed (in bits per second) to pass to the PPP daemon as the interface speed for the tty/pty pair. This is ignored by some PPP daemons, such as Linux's pppd(8). The default is 115200 bytes per second, which some implementations interpret as meaning "no limit". Equivalent to the command line --speed option. NOTES
An ip-specification above (for the localip and remoteip tags) may be a list of IP addresses (for example 192.168.0.2,192.168.0.3), a range (for example 192.168.0.1-254 or 192.168.0-255.2) or some combination (for example 192.168.0.2,192.168.0.5-8). For some valid pairs might be (depending on use of the VPN): localip 192.168.0.1 remoteip 192.168.0.2-254 or localip 192.168.1.2-254 remoteip 192.168.0.2-254 ROUTING CHECKLIST - PROXYARP Allocate a section of your LAN addresses for use by clients. In /etc/ppp/options.pptpd. set the proxyarp option. In pptpd.conf do not set localip option, but set remoteip to the allocated address range. Enable kernel forwarding of packets, (e.g. using /proc/sys/net/ipv4/ip_forward ). The server will advertise the clients to the LAN using ARP, providing it's own ethernet address. bcrelay(8) should not be required. ROUTING CHECKLIST - FORWARDING Allocate a subnet for the clients that is routable from your LAN, but is not part of your LAN. In pptpd.conf set localip to a single address or range in the allocated subnet, set remoteip to a range in the allocated subnet. Enable kernel forwarding of packets, (e.g. using /proc/sys/net/ipv4/ip_forward ). The LAN must have a route to the clients using the server as gateway. The server will forward the packets unchanged between the clients and the LAN. bcrelay(8) will be required to support broadcast protocols such as NETBIOS. ROUTING CHECKLIST - MASQUERADE Allocate a subnet for the clients that is not routable from your LAN, and not otherwise routable from the server (e.g. 10.0.0.0/24). Set localip to a single address in the subnet (e.g. 10.0.0.1), set remoteip to a range for the rest of the subnet, (e.g. 10.0.0.2-200). Enable kernel forwarding of packets, (e.g. using /proc/sys/net/ipv4/ip_forward ). Enable masquerading on eth0 (e.g. iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE ). The server will translate the packets between the clients and the LAN. The clients will appear to the LAN as having the address corre- sponding to the server. The LAN need not have an explicit route to the clients. bcrelay(8) will be required to support broadcast proto- cols such as NETBIOS. FIREWALL RULES
pptpd(8) accepts control connections on TCP port 1723, and then uses GRE (protocol 47) to exchange data packets. Add these rules to your iptables(8) configuration, or use them as the basis for your own rules: iptables --append INPUT --protocol 47 --jump ACCEPT iptables --append INPUT --protocol tcp --match tcp --destination-port 1723 --jump ACCEPT SEE ALSO
pppd(8), pptpd(8), pptpd.conf(5). 29 December 2005 PPTPD.CONF(5)
All times are GMT -4. The time now is 05:11 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy