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Full Discussion: routing and firewall
Top Forums UNIX for Advanced & Expert Users routing and firewall Post 302318464 by meorfi on Thursday 21st of May 2009 03:22:52 PM
Old 05-21-2009
routing and firewall

I have a PC with KUBUNTU installed on it and with 2NIC's on it (two PCI network 100Mbit cards). I want to use it as a server packet router and firewall between two computers with windows installed on them, each of this computer being connected to one different card on the KUBUNTU server. The computers are connected to the network cards using a switch.
I tried to configure the server to route the packets from one IP address rank to another and with different masks, but I hadn't managed to do this. Instead I did the following:
1. I've set net.ipv4.ip_forward = 1 in sysctl.conf
2. I configured eth0 as follows:
ifconfig eth0 192.168.2.1 netmask 255.255.255.0 up
3. I configured eth1 as follows:
ifconfig eth1 192.168.1.2 netmask 255.255.255.0 up

After this I managed to ping say a computer with Windows with 192.168.1.5 from a computer connected to another card with the IP address 192.168.2.5.

(But initially I wanted to ping say a computer with the IP with 81.180.75.70(mask 255.255.255.192) from a computer with the IP of 192.168.2.5(mask 255.255.255.0) -> I didn't managed to do that)

NEXT, I want to configure the server to act as a firewall. Let say he will allow ping from one PC connected to the server to another one but not viceversa. At the same time I want that ping(or say packets) from the PCs will reach the server and viceversa. (So finally to deny ping from one PC to another, but another will be able to ping the one whose packets will be rejected).

I tried to do something like this:

iptables -A FORWARD -s 0/0 -i eth0 -d 192.168.1.5 -o eth1 -j REJECT

but this isn't working.
If I do this, on one PC ping will result in Request timed out,
and on another will result in some specific reject message. If I
remove this by typing iptables -F FORWARD, everything goes back
to normal and ping is allowed.

WHAT'S THE PROBLEM? CAN SOMEONE EXPLAIN STEP BY STEP WHAT I NEED TO DO?
THANKS IN ADVANCE TO EVERYONE WHO'LL TRY TO HELP ME!

PLEASE DON'T ASK WHY I NEED THAT AND WHY THIS VERSION OF LINUX(UBUNTU)
BECAUSE THE TASK IS SUPPOSED TO BE RESOLVED WITH THIS CONFIGURATION
AND NO MORE!
 

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FIREWALLD.ZONES(5)						  firewalld.zones						FIREWALLD.ZONES(5)

NAME
firewalld.zones - firewalld zones DESCRIPTION
What is a zone? A network zone defines the level of trust for network connections. This is a one to many relation, which means that a connection can only be part of one zone, but a zone can be used for many network connections. The zone defines the firewall features that are enabled in this zone: Predefined services A service is a combination of port and/or protocol entries. Optionally netfilter helper modules can be added and also a IPv4 and IPv6 destination address. Ports and protocols Definition of tcp or udp ports, where ports can be a single port or a port range. ICMP blocks Blocks selected Internet Control Message Protocol (ICMP) messages. These messages are either information requests or created as a reply to information requests or in error conditions. Masquerading The addresses of a private network are mapped to and hidden behind a public IP address. This is a form of address translation. Forward ports A forward port is either mapped to the same port on another host or to another port on the same host or to another port on another host. Rich language rules The rich language extends the elements (service, port, icmp-block, masquerade and forward-port) with additional source and destination addresses, logging, actions and limits for logs and actions. It can also be used for host or network white and black listing (for more information, please have a look at firewalld.richlanguage(5)). For more information on the zone file format, please have a look at firewalld.zone(5). Which zones are available? Here are the zones provided by firewalld sorted according to the default trust level of the zones from untrusted to trusted: drop Any incoming network packets are dropped, there is no reply. Only outgoing network connections are possible. block Any incoming network connections are rejected with an icmp-host-prohibited message for IPv4 and icmp6-adm-prohibited for IPv6. Only network connections initiated within this system are possible. public For use in public areas. You do not trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted. external For use on external networks with masquerading enabled especially for routers. You do not trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted. dmz For computers in your demilitarized zone that are publicly-accessible with limited access to your internal network. Only selected incoming connections are accepted. work For use in work areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted. home For use in home areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted. internal For use on internal networks. You mostly trust the other computers on the networks to not harm your computer. Only selected incoming connections are accepted. trusted All network connections are accepted. Which zone should be used? A public WIFI network connection for example should be mainly untrusted, a wired home network connection should be fairly trusted. Select the zone that best matches the network you are using. How to configure or add zones? To configure or add zones you can either use one of the firewalld interfaces to handle and change the configuration: These are the graphical configuration tool firewall-config, the command line tool firewall-cmd or the D-BUS interface. Or you can create or copy a zone file in one of the configuration directories. /usr/lib/firewalld/zones is used for default and fallback configurations and /etc/firewalld/zones is used for user created and customized configuration files. How to set or change a zone for a connection? The zone is stored into the ifcfg of the connection with ZONE=option. If the option is missing or empty, the default zone set in firewalld is used. If the connection is controlled by NetworkManager, you can also use nm-connection-editor to change the zone. SEE ALSO
firewall-applet(1), firewalld(1), firewall-cmd(1), firewall-config(1), firewalld.conf(5), firewalld.direct(5), firewalld.icmptype(5), firewalld.lockdown-whitelist(5), firewall-offline-cmd(1), firewalld.richlanguage(5), firewalld.service(5), firewalld.zone(5), firewalld.zones(5) NOTES
firewalld home page at fedorahosted.org: http://fedorahosted.org/firewalld/ More documentation with examples: http://fedoraproject.org/wiki/FirewallD AUTHORS
Thomas Woerner <twoerner@redhat.com> Developer Jiri Popelka <jpopelka@redhat.com> Developer firewalld 0.3.9 FIREWALLD.ZONES(5)
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