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 From:  =?ISO-8859-1?Q?Michael_=D8stergaard_Pedersen?= <michael at bytopia dot dk>
 To:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] Problem with static routes
 Date:  Sat, 15 May 2004 21:17:28 +0200

Thanks for the reply. I was considering the non-symmetric routes as a 
problem, but since TCP connections are identified by source, source port, 
destination and destination port I didn't think that it would be a problem 
as long as the other host received it's packets. As far as I know the whole 
idea of the Internet is that the host doesn't care how the packets are 
routed to their destination.

There seems to be some confusion about states since the m0n0wall are 
dropping packets that are clearly allowed in my firewall rules and my guess 
is that if these packets made it to their destination the destination would 
reply correctly.

A static route on all hosts on the LAN works fine, but the was 
just an example. We have over 30 subnets on that MPLS connection and over 40 
workstations on the LAN. Managing static routes is something that I would 
prefer to be without :)

Putting the router on a separate interface on the m0n0wall is something we 
will do in the future, but right now we just need something that works as it is.


 > Hi Michael,
 > this problem is due to the non-symmetric route the packets are following
 > (well, at leastI think it is). Not all protocols are so happy about that, or
 > m0n0wall could get confused about states and start blocking packets
 > (somebody please correct me if I'm wrong).
 > In fact, all your hosts on the LAN network should have a static route to
 > that network, or you should put your router on a separate
 > interface of the m0n0.
 > Regards,
 > Joachim
>>From: Michael Østergaard Pedersen [mailto:michael at bytopia dot dk]
>>Sent: zaterdag 15 mei 2004 13:27
>>To: m0n0wall at lists dot m0n0 dot ch
>>Subject: [m0n0wall] Problem with static routes
>>I have a strange problem with m0n0wall and static routes. My 
>>network looks
>>like this:
>>    Default GW
>>        |
>>       WAN
>>        |
>>    +--------+
>>    |m0n0wall|---DMZ
>>    +--------+
>>        |
>>       LAN---- ..-
>>My LAN subnet is and the .254 machine is a 
>>router that can 
>>reach the network via some MPLS network.
>>I have added a static route to the LAN interface on the 
>>m0n0wall to reach 
>>the network via
>>When I try to reach from my LAN using the m0n0wall 
>>as a default 
>>gateway strange things happen. If I ping from LAN 
>>I get a reply 
>>and I can see that ICMP redirects are being sent to tell me that 
>> is a more direct route to that host. This is 
>>fine. If I try to 
>>SSH to that host I am prompted for a password. If I enter the 
>>correctly the connection hangs. When I check the logs on the 
>>m0n0wall I see 
>>the following:
>>22:29:23.387117 dc0 @0:68 b,40452 -> 
>>,22 PR tcp len
>>20 64 -A IN
>>22:29:23.349785 dc0 @0:68 b,40452 -> 
>>,22 PR tcp len
>>20 436 -AP IN
>>Does this mean that this traffic is being dropped by the m0n0wall? It
>>doesn't make sense to me since dc0 is my LAN interface and I 
>>have a rule to
>>permit all traffic coming in on the LAN interface.
>>Also since I do get the password prompt from SSH some packets 
>>do in fact get 
>>through. Perhaps only the first one or two?
>>Any help is appreciated. I can post more info if you need it.