Date: Fri, 17 Mar 2006 21:48:49 -0800 From: ray@redshift.com To: Glenn Dawson <glenn@antimatter.net>,freebsd-hackers@freebsd.org Subject: Re: strange ARP problem Message-ID: <3.0.1.32.20060317214849.00c00778@pop.redshift.com> In-Reply-To: <7.0.1.0.2.20060317205230.057ba948@antimatter.net> References: <3.0.1.32.20060317203432.00bf8a40@pop.redshift.com> <441B09DA.1010902@elischer.org> <200603171502.k2HF2IV3086523@pinky.frank-behrens.de> <20060317151220.GA26987@britannica.bec.de> <441B09DA.1010902@elischer.org> <3.0.1.32.20060317203432.00bf8a40@pop.redshift.com>
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At 08:59 PM 3/17/2006 -0800, Glenn Dawson wrote: | At 08:34 PM 3/17/2006, ray@redshift.com wrote: | >I'm having a strange issue here and thought maybe someone on this list might | >have some ideas. I have tried to figure it out for a couple of days, but no | >luck yet. The problem seems to be around reporting of arp information. | > | >Here is my basic config. I have my workstation (a windows XP box) with 2 IP's | >on a private network segment (both with /24 subnet masks) | > | >192.168.10.250 | >192.168.20.250 | > | >the 10.250 and 20.250 are connected out to a small switch. Also connected to | >that small switch is a mail server as shown below. | > | >[ workstation ] [ mail server ] | >[192.168.10.250]-------[ small ]--------[ 192.168.10.15] | >[192.168.20.250]-------[ switch ]--------[ 192.168.20.15] | > | | > | | > [router 192.168.10.1] | > | | > public IP | > | >10.15 handles SMTP to the public, 20.15 is for admin and POP to/from the | >workstation on 20.250 | > | >Okay, so the problem is that when I fire up the Workstation (it's running | >Windows XP), the arp data for 192.168.20.15 comes back with the incorrect Mac | >address. It ends up with the Mac address for 10.15, instead of 20.15 - which | >keeps the machines from talking correctly. If you delete the ARP table and | >re-arp, then it's perfectly fine from then on. Totally odd. | > | >Then the other night I noticed the following errors (see below) from the mail | >server. It seems to be related, but I can't pin point the source or | >what might | >cause something like this. | > | >Does anyone have any ideas what could be causing this? | > | > > arp: 192.168.10.1 is on fxp0 but got reply from 00:30:48:52:08:03 on bge0 | > > arp: 192.168.20.250 is on bge0 but got reply from 00:e0:81:32:e0:a0 on fxp0 | > > arp: 00:30:48:51:ce:f0 is using my IP address 192.168.20.15! | > > arp: 00:30:48:51:ce:f0 is using my IP address 192.168.20.15! | > > arp: 192.168.10.1 is on fxp0 but got reply from 00:30:48:52:08:03 on bge0 | > > arp: 00:30:48:51:ce:f0 is using my IP address 192.168.20.15! | > > arp: 192.168.10.15 is on lo0 but got reply from 00:30:48:51:ce:f0 on bge0 | > > arp: 192.168.10.1 is on fxp0 but got reply from 00:30:48:52:08:03 on bge0 | > > arp: 192.168.10.15 is on lo0 but got reply from 00:30:48:51:ce:f0 on bge0 | > > arp: 192.168.20.250 is on bge0 but got reply from 00:e0:81:32:e0:a0 on fxp0 | > > arp: 192.168.10.15 is on lo0 but got reply from 00:30:48:51:ce:f0 on bge0 | > > arp: 192.168.10.1 is on fxp0 but got reply from 00:30:48:52:08:03 on bge0 | > | >here is the ifconfig from the mail server: | > | >[ray@mail ray]$ ifconfig | >fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 | > inet 192.168.10.15 netmask 0xffffff00 broadcast 192.168.10.255 | > ether 00:30:48:51:ce:f0 | > media: Ethernet autoselect (100baseTX <full-duplex>) | > status: active | >bge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500 | > options=1b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING> | > inet 192.168.20.15 netmask 0xffffff00 broadcast 192.168.20.255 | > ether 00:30:48:51:ce:f1 | > media: Ethernet autoselect (100baseTX <full-duplex>) | > status: active | >lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384 | > inet 127.0.0.1 netmask 0xff000000 | > | >If anyone has any idea, please let me know. Thanks! | | This is exactly why it's ill-advised to have two network interfaces | on different networks connected to the same physical network. | | If you actually need two different networks (although from your | description I don't see a reason why you would) then use a single | physical interface and assign it an IP from each network. Or, get a | switch that has VLAN capabilities and keep the two networks separated. | | -Glenn The switch should act as a bridge - so from the standpoint of the computers, shouldn't it effectively be two different networks? In other words, if I ran 20.x across a different switch, would that matter? I've always understood that a switch was something you viewed as basically a bunch of individual little bridges. I can drag out another switch and test that idea and see if the problem goes away. This problem did start when I ran everything through 1 switch - I just didn't think that would any specific negative impact. Thanks for the note back Glenn :-) Ray
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