[LARTC] DNAT and Load Balancing

[Tom Lobato]

    Hi all!


    After that good thread "DGD patch not detecting dead gateway" I was 
able to set up a Load Balancing with ping based DGD (without Julian 
Anastasov patch). But now I'm facing a new problem and tried some 
options, with only partial solutions.

    I made a script based on 
http://www.mail-archive.com/lartc@mailman.ds9a.nl/msg16257.html (Thank 
you Manish Kathuria), without Julian A. patch, and with routes/rules as 
described in nano.txt. It works fine, but...

    The problem: I do DNAT for internet located people to access my LAN 
machines (VNC, RDP, etc...). It sometimes works, sometimes don't work. 
It appears that the connection from outside can enter, but when reply 
packets try to get back across nat machine, it falls into the round 
robin default route selection to define its gateway. Well, of course, 
this reply must leave the router via the same interface whose initial 
packets entered.


    vnc initial
request packet      reply that got
            \                   wrong route
             \                       ^
              \                     /
              V                  /
              isp1 isp2 isp3
               _|____|____|__
              |                    |
              |      dnat      |
              |_____________|
                        ^
                         |
                         |
                        V
              LAN estation, the
                  vnc server



    What I need is a way to force packets leave the router via the same 
interface whose its request entered this.
    I'd like to hear opinions about the problem (and also solution =). 
Remember, I can't apply the DGD patch from J.A. because it only checks 
the first hop for dead detection.
    I will apreciate any help.

    Thank you,



    Tom Lobato