Re: [LARTC] ABout Routing..again

[Dhirendra Pal Singh <list@actiswitch.com>]

Thanks a lot once again Martin.
Yes this is the correct diagra.
Mean while I have agian posted my question with the diagram fixed. 
Please ignore it.

Got your point Martin about why its not working. I will try it later again.
I apologise for posting the wrong question.. and thank once again to 
Martin for taking the pains to correct the diagram and sending and 
answer. I was in a fix and didnt knew where to send the question. I 
paniced.. sorry..


I will take care of this in future..
Thanks
Dp



Martin A. Brown wrote:

>Dhirendra,
>
> : Dsl feed goes to gateway 1. Its internal ip address is of 192.168.1.XXX.
> : Now from here goes the feed to another gateway which eth0 ip address is
> : 192,168.1.50. It has 2 more eth - eth1 and eth2. Their ip address are
> : 192.168.2.51 and 192.168.3.XXX respectively.
> : Now my problem is that all the computers connect to 192.168.2.XXX are
> : unable to point to the computers of 192.168.1.XXX. Though strangely I
> : can ping to 192.168.1.1 wich is the internal ip address of the gateway 1.
>
>Is this your network, or did I mangle it in reconstruction?
>
>
>                                          eth0
>                                        192.168.1.50
>                                               \
>           |----------|                         |----------|
>           | gateway 1|-------------------------| gateway2 |
>          /|__________|\          |             |----------|
>         /              \         |             /         \
>      eth0             eth1       |            /           \
>  61.X.X.X          192.168.1.1   |          eth1          eth2
>(public)                          |       192.168.2.51     192.168.3.52
>                                  |                         |
>                         ------------                       |
>                         |  BOX 1   |                  -------------
>                         ------------                  |   Box 3   |
>                         192.168.1.101                 -------------
>                                                      192.168.3.101
>
>
>You can ping 192.168.1.1 because it is a locally hosted IP on the default
>gateway of the machines in the 192.168.2.0/24 network.
>
> : I have the following setup on redhat linux 8.0 ...
> :
> : A) I am unable to ping from Box 3 (192.168.3.101) to Box 1. Any
> :    comments or reasons why?
>
>It looks like you have a common routing problem.  If you examine the
>routing tables on gateway 1 and box 1, they are probably missing routes
>to 192.168.3.0/24 and 192.168.2.0/24 via 192.168.1.50.  Host 1 probably
>has a default route to 192.168.1.1 and gateway 1 certainly doesn't have a
>default route pointing *into* your network.
>
><gripe>
>This is not really a LAR (and certainly not a TC) question.  This is a
>basic routing question.  Let's try to keep these questions off the LARTC
>list....this is probably better for a forum like comp.os.linux.networking
>or a LUG.
></gripe>
>
><helpful-hat>
>You may find some of my documentation useful in conceptualizing static
>routing:
>
>  http://linux-ip.net/
>  http://linux-ip.net/html/ch-routing.html
>
>For others who are following along with questions like this, I would
>recommend using a network analyzer of some kind to look at the packets on
>each of the machines involved.
>
>  - use tcpdump or ethereal on each affected router and end-host
>  - generate regular traffic (ping, nc, socat, etc.) while trying to
>    determine where the packets are getting dropped or misrouted
></helpful-hat>
>
>So, Dhirendra:
>
>Remove the masquerading from gateway2
>
>[root@box1]# ip route add 192.168.3.0/24 via 192.168.1.50
>[root@box1]# ip route add 192.168.2.0/24 via 192.168.1.50
>[user@box3]$ ping -n 192.168.1.101
>
>You should get a response.
>
>[root@box2]# ip route add 192.168.3.0/24 via 192.168.1.50
>[root@box2]# ip route add 192.168.2.0/24 via 192.168.1.50
>
> : B) I have figured out that if I enable Masquerading then problem A is
> :    solved. Can someone explain why?
>
>Because you are changing the source IP on the packets to a 192.168.1.0/24.
>When you do this, the other hosts in 192.168.1.0/24 have a direct route
>for reply packets.
>
> : C) Is it possible without Masquerading ?
>
>Yes.
>
>-Martin
>
>Anybody think a LARTC FAQ is a good idea?
>
>  
>


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