Re: [LARTC] Traceroute looks good, but packets destined for wrong MAC

From: Guy Van Den Bergh <guy.vandenbergh@pandora.be>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Traceroute looks good, but packets destined for wrong MAC
Date: Tue, 29 May 2001 23:24:51 +0000	[thread overview]
Message-ID: <marc-lartc-99117889708111@msgid-missing> (raw)
In-Reply-To: <marc-lartc-99117093317802@msgid-missing>

I should go to bed, I was not thinking clear either. :(
Please ignore my previous message :)

Jeffrey W. Baker wrote:

> Hello,
> 
> I am a newbie at routing configuration and I hope you can help me
> understand why something is happening, and how I can reconfigure my
> machine to work correctly.  Here is my network setup:
> 
> [DSL Router]          [T1 Router]
>      |                     |65.198.37.65
> [NAT/firewall]             |
>      |192.168.168.1        |
>      +-----------+---------+
>                  |
>              [switch]
>                  |
>                  |
>                  +-------[Linux box]
>                          192.168.168.200/eth0
>                          65.198.37.66/eth0
> 
> You can see, I have two IPs of different nets bound to the single
> interface in the machine.  My goal is to route connections over both the
> DSL and the (fractional) T1, preferring the DSL with a 6:1 ratio.
> Here is my configuration so far, which mostly works:
> 
> root@windmill:/home/jwb# ip route list
> 65.198.37.64/29 dev eth0  proto kernel  scope link  src 65.198.37.66
> 192.168.168.0/24 dev eth0  proto kernel  scope link  src 192.168.168.200
> 127.0.0.0/8 dev lo  scope link
> default
> 	nexthop via 192.168.168.1  dev eth0 weight 6
> 	nexthop via 65.198.37.65  dev eth0 weight 1
> 
> root@windmill:/home/jwb# ip route list table 100
> 192.168.168.0/24 dev eth0  scope link
> default via 192.168.168.1 dev eth0
> 
> root@windmill:/home/jwb# ip route list table 200
> 65.198.37.64/29 dev eth0  scope link
> default via 65.198.37.65 dev eth0
> 
> root@windmill:/home/jwb# ip addr list
> 1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
>     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
>     inet 127.0.0.1/8 scope host lo
> 2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
>     link/ether 00:d0:b7:88:23:d9 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.168.200/24 brd 192.168.168.255 scope global eth0
>     inet 65.198.37.66/29 scope global eth0:t1
> 
> root@windmill:/home/jwb# ip ru list
> 0:	from all lookup local
> 32764:	from 65.198.37.66 lookup 200
> 32765:	from 192.168.168.1 lookup 100
> 32766:	from all lookup main
> 32767:	from all lookup 253
> 
> This mostly works fine, except that a lot of packets are going out over
> one link or the other, with the wrong source address.  Also traceroute
> shows packets going out over the DSL, which actual TCP SYN packets go out
> over the T1 with the wrong address.  Here is an example:
> 
> traceroute to appwatch.zdnet.com (216.65.128.201), 30 hops max, 40 byte
> packets
>  1  w145.z064001233.sjc-ca.dsl.cnc.net (64.1.233.145)
>  2  w001.z064001104.sjc-ca.dsl.cnc.net (64.1.104.1)
> 
> So the packets should be going out over the DSL.  However, ethereal shows
> that when I try to initiate a TCP connection, the packets are headed for
> the MAC address of corresponding to the T1 router (65.198.37.65).  Why
> would this discrepancy happen?
> 
> Regards and thanks in advance for any assistance,
> Jeffrey Baker
> 
> 
> _______________________________________________
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> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/
> 
> 
> 

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