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From: Jarek Sobieszek <j.sobieszek@lart.pl>
To: netfilter@lists.netfilter.org
Subject: loopback and pointopoint interfaces
Date: Thu, 30 Jan 2003 12:00:35 +0100	[thread overview]
Message-ID: <20030130110035.GA3701@localhost.localdomain> (raw)

Hello,

I have some problems testing local interfaces over loopback.

Consider the following setup:

if0: 10.1.1.1 pointopoint 10.1.1.12
if1: 10.1.1.2 pointopoint 10.1.1.11

cable connects if0 with if1

iptables -A POSTROUTING -t nat -d 10.1.1.11 -j SNAT --to 10.1.1.12
iptables -A POSTROUTING -t nat -d 10.1.1.12 -j SNAT --to 10.1.1.11
iptables -A PREROUTING -t nat -d 10.1.1.11 -j DNAT --to 10.1.1.1
iptables -A PREROUTING -t nat -d 10.1.1.12 -j DNAT --to 10.1.1.2

ping 10.1.1.11 and ping 10.1.1.12 work as expected

Here's what I believe is going on:

ping 10.1.1.11
src             dst
10.1.1.2      10.1.1.11
POSTROUTING(if1)
10.1.1.12    10.1.1.11
OUT: if1
IN: if0
10.1.1.12    10.1.1.11
PREROUTING(if0)
10.1.1.12    10.1.1.1
ICMP
10.1.1.1      10.1.1.12
POSTROUTING(if0)
10.1.1.11    10.1.1.12
OUT: if0
IN: if1
10.1.1.11    10.1.1.12
PREROUTING(if1)
10.1.1.11    10.1.1.2
ping response from 10.1.1.2

Now the setup which I cannot make to work:

if0: 10.1.1.1 pointopoint 10.1.1.12
if1: 10.1.1.3 pointopoint 10.1.1.14
if2: 10.1.1.4 pointopoint 10.1.1.13
if3: 10.1.1.2 pointopoint 10.1.1.11

cables connect if0 to if1 and if2 to if3

iptables -A POSTROUTING -t nat -d 10.1.1.11 -j SNAT --to 10.1.1.3
iptables -A POSTROUTING -t nat -d 10.1.1.12 -j SNAT --to 10.1.1.4
iptables -A POSTROUTING -t nat -d 10.1.1.13 -j SNAT --to 10.1.1.11
iptables -A POSTROUTING -t nat -d 10.1.1.14 -j SNAT --to 10.1.1.12
iptables -A PREROUTING -t nat -d 10.1.1.11 -j DNAT --to 10.1.1.14
iptables -A PREROUTING -t nat -d 10.1.1.12 -j DNAT --to 10.1.1.13
iptables -A PREROUTING -t nat -d 10.1.1.13 -j DNAT --to 10.1.1.2
iptables -A PREROUTING -t nat -d 10.1.1.14 -j DNAT --to 10.1.1.1

ping 10.1.1.1 and ping 10.1.1.2 don't work

Here's what I believe should be going on (but apparently it isn't):

ping 10.1.1.11
src             dst
10.1.1.2      10.1.1.11
POSTROUTING(if3)
10.1.1.3      10.1.1.11
OUT: if3
IN: if2
10.1.1.3      10.1.1.11
PREROUTING(if2)
10.1.1.3      10.1.1.14 (FWD)
POSTROUTING(if1)
10.1.1.12    10.1.1.14
OUT: if1
IN: if0
10.1.1.12    10.1.1.14
PREROUTING(if0)
10.1.1.12    10.1.1.1
ICMP
10.1.1.1      10.1.1.12
POSTROUTING(if0)
10.1.1.4      10.1.1.12
OUT:if0
IN:if1
10.1.1.4      10.1.1.12
PREROUTING(if1)
10.1.1.4      10.1.1.13 (FWD)
POSTROUTING(if2)
10.1.1.11    10.1.1.13
OUT:if2
IN:if3
10.1.1.11    10.1.1.13
PREROUTING(if3)
10.1.1.11    10.1.1.2
ping response from 10.1.1.2

Any ideas why it doesn't work (I enabled ip_forward and disabled 
rp_filter)?
And is it posible to blindly forward packets from if1/if2 to if2/if1 
(since the devices are not ehernet I think ethernet bridging does not 
qualify)?

Thanks,

Jarek Sobieszek


             reply	other threads:[~2003-01-30 11:00 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-01-30 11:00 Jarek Sobieszek [this message]
     [not found] ` <20030130143348.GC8060@localhost.localdomain>
2003-01-30 14:35   ` loopback and pointopoint interfaces Jarek Sobieszek
2003-01-30 16:45     ` Jarek Sobieszek

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