LARTC - Feb 2003 - Problem .....

Hi,
My Problem is like this.....

I have 2 interfaces eth0 and eth1 
IPaddress at eth0 is 132.147.165.1 and eth1 is
202.88.151.1. 
I have a LAN of 132.165.0.0 network and all the
computers in this network access the internet via NAT
that is done by my linux m/c having ipaddress
132.147.165.1.
Natting is done via iptables with the following
options.
iptables -t nat -A POSTROUTING -o eth1 -j SNAT --to
202.88.151.1 
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE  

Now I am interested in bandwidth management .
So I have introduced qdisc through tc at both the
interface.

I used HTB as such after applying the patch.
I associated filters using internal IPaddresses for
both the interface.
At eth0 all the packets are going to the properly
assigned queue while at interface eth1 all the packets
went through default queue as no packet matched the
filters. This is because the packets are Natted.

Is it possible that when the packets arrive from eth0 
to eth1 no natting is done and at the time of xmit at
eth1 Natting takes place.
Similarly, when the packet comes from eth1 first
Natting takes place and is then queued.

Presently the packet is not getting bandwidth managed
fully as eth1 has no management. 

waiting for replies

thanks
bhik


__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/

Dear bhik,

You have a reasonable question which gets asked often here in many
different forms.  It should not be hard for you to answer the question for
yourself by examining the kernel packet traveling diagram on
www.docum.org:

  http://www.docum.org/stef.coene/qos/kptd/

 : This is because the packets are Natted. Is it possible that when the
 : packets arrive from eth0 to eth1 no natting is done and at the time of
 : xmit at eth1 Natting takes place.

Your supposition is absolutely correct.  You might consider using the
iptables MARK target to tag the desired packets and apply traffic control
based on this fwmark on the packet.  See the discussion of fwmark and
queuing at LARTC:

  http://lartc.org/howto/lartc.qdisc.filters.html

 : iptables -t nat -A POSTROUTING -o eth1 -j SNAT --to 202.88.151.1
 : iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

I''d also caution you to decide whether you are using SNAT or
MASQUERADE.
If the iptables rules are entered in this order on your publicly addressed
host, then your "-j MASQUERADE" rule is extraneous.

For an explanation of the difference between SNAT and MASQUERADE, consult

  http://iptables-tutorial.frozentux.net/iptables-tutorial.html#MASQUERADETARGET
  http://iptables-tutorial.frozentux.net/iptables-tutorial.html#SNATTARGET

Good luck,

-Martin

-- 
Martin A. Brown --- SecurePipe, Inc. --- mabrown@securepipe.com

_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/