Three Tables in IPTABLES

winxandlinx · 11-17-2006, 01:45 AM

hi everyone

iptables i can understand filter table and nat table

i cannot able to understand what is mangle

Please anyone can explain me that

Helping this issue will be greatly appricaited

Nathanael · 11-17-2006, 04:14 AM

read this :-)

http://iptables-tutorial.frozentux.n...ml#MANGLETABLE

winxandlinx · 11-17-2006, 05:53 AM

ya i read it already

i cannot able to understand thats the reason posted here

Can you please tell me in your own way and also tell me where

and when it will be used in the real time

Helping this will be geratly appriciated

Thankswinxandlinx

Nathanael · 11-17-2006, 06:04 AM

it says is right there on that page

Quote:

The following targets are only valid in the mangle table. They can not be used outside the mangle table.

* TOS
* TTL
* MARK

The TOS target is used to set and/or change the Type of Service field in the packet. This could be used for setting up policies on the network regarding how a packet should be routed and so on.
[...]

The TTL target is used to change the TTL (Time To Live) field of the packet. We could tell packets to only have a specific TTL and so on. One good reason for this could be that we don't want to give ourself away to nosy Internet Service Providers. Some Internet Service Providers do not like users running multiple computers on one single connection, and there are some Internet Service Providers known to look for a single host generating different TTL values, and take this as one of many signs of multiple computers connected to a single connection.

The MARK target is used to set special mark values to the packet. These marks could then be recognized by the iproute2 programs to do different routing on the packet depending on what mark they have, or if they don't have any. We could also do bandwidth limiting and Class Based Queuing based on these marks.

TOS is the TypeOfService of the packet
TTL is the TimeToLive of a packet
MARK is a marker you can assign to a packet

so what you get out of those 3 paragraphs is that you are changing information in the packet itself. (or in the case of MARK you are marking it to recognize the packet elsewhere again)

if you dont know what it means to change these fields in a packet or what you would do with this feature of iptables, then basically ignore the table MANGLE and you will be fine.

osor · 11-17-2006, 09:47 AM

You didn't even mention the fourth netfilter table (raw), whose purpose is even more cryptic (to prevent tracking of high-volume types of packets).

Nathanael · 11-17-2006, 09:48 AM

com'on dont confuse the poor guy :-)