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-   -   How actually packet traverse in IPTables (http://www.linuxquestions.org/questions/linux-networking-3/how-actually-packet-traverse-in-iptables-703340/)

priyadarshan 02-09-2009 08:09 AM

How actually packet traverse in IPTables
 
I am student of computer engineering, working on firewall project using IPtables.....I am little bit confused about packet flow in firewall..I saw the diagrams showing packet flow in IPTables.....I am quite confused...

(1) In the packet flow diagram, two networks are shown by using clouds....now pls tell me that which is public and which is private network?

(2) What are the conditions or parameters that determine weather the packet is for local process or not....I mean weather to put packet in INPUT chain or FORWARD chain?

(3) If packet is for local process than it goes to the INPUT chain....Now I want to know that what is local process really???.....If I have firewall than what may local process....I mean only internal host from private network will talk to remote servers....so data is generated by these two ends only ( I think so) ....than where does the local process of firewall ( Also written that local process generates packet) comes into the picture..


Pls pls pls respond me.....

win32sux 02-09-2009 10:15 AM

Quote:

Originally Posted by priyadarshan (Post 3437123)
I am student of computer engineering, working on firewall project using IPtables.....I am little bit confused about packet flow in firewall..I saw the diagrams showing packet flow in IPTables.....I am quite confused...

(1) In the packet flow diagram, two networks are shown by using clouds....now pls tell me that which is public and which is private network?

(2) What are the conditions or parameters that determine weather the packet is for local process or not....I mean weather to put packet in INPUT chain or FORWARD chain?

(3) If packet is for local process than it goes to the INPUT chain....Now I want to know that what is local process really???.....If I have firewall than what may local process....I mean only internal host from private network will talk to remote servers....so data is generated by these two ends only ( I think so) ....than where does the local process of firewall ( Also written that local process generates packet) comes into the picture..


Pls pls pls respond me.....

I know for a fact that every single one of your questions is answered in the most popular iptables tutorial ever written. A private network uses IP addresses which aren't globally assigned. A packet will traverse INPUT if the source IP on it matches an IP assigned to the box it has come into contact with (otherwise, it will traverse FORWARD).

priyadarshan 02-10-2009 07:47 AM

Actually I read this before but I couldnt get it...I mean I am confused.......

OK tell me that suppose I have IPTable configured firewall on my box than according to the diagram of packet traversing in IPTables, the local process will be my browser or anything which generates IP packets...it may my proxy server too...( M I right???....pls clear my confusion )

OK now here we have configured firewall on our box and we are sending packet from only our box so Local process is as I specified above.....


BUT BUT BUT.........

What if the firewall is configured on UTM machine or say on my GATEWAY machine, which is not really used for sending packet.......????.........More clearly I am telling that

If I have joined three machines to one other machine which acts as GATEWAY or to UTM machine than what will be the local process now.......How the packet will traverse.....


Pls Pls Pls answer me.........

win32sux 02-10-2009 11:26 AM

Quote:

Originally Posted by priyadarshan (Post 3438368)
Actually I read this before but I couldnt get it...I mean I am confused.......

OK tell me that suppose I have IPTable configured firewall on my box than according to the diagram of packet traversing in IPTables, the local process will be my browser or anything which generates IP packets...it may my proxy server too...( M I right???....pls clear my confusion )

OK now here we have configured firewall on our box and we are sending packet from only our box so Local process is as I specified above.....


BUT BUT BUT.........

What if the firewall is configured on UTM machine or say on my GATEWAY machine, which is not really used for sending packet.......????.........More clearly I am telling that

If I have joined three machines to one other machine which acts as GATEWAY or to UTM machine than what will be the local process now.......How the packet will traverse.....


Pls Pls Pls answer me.........

Not sure I understand what you mean, but as far as the filter table, the INPUT/OUTPUT chains would be used by the clients, while the FORWARD chain would used by the gateway. BTW, I'm moving this to Networking for better exposure.


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