From: Grant Taylor <gtaylor@riverviewtech.net>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Mulitple VLANs containing the same ip subnet NATed on
Date: Sat, 08 Jul 2006 21:49:00 +0000 [thread overview]
Message-ID: <44B0284C.6010104@riverviewtech.net> (raw)
In-Reply-To: <78f747be0607081414i5ad45c8cqe07c309bd080d0@mail.gmail.com>
Geoff Karl wrote:
> Thanks for the reply Grant.
You are welcome.
> What would happen if workstations on the "workstations" vlan had the
> same ip addresses? Can i bridge two networks that have the same ip
> addresses without getting errors.
Well, seeing as how bridging (EBTables) is a layer 2 bridge, there would be no problem with having the same subnet on both sides of the bridge. Now if you are asking if there would be a problem with a workstation on VLAN 1 having the same IP as a workstation on VLAN 2, then you would end up with the same situation that you would as if both workstations were on the same VLAN. However, that being said, if these two workstations never needed to talk there are some things that you can do. You can set up some EBTables filtering rule to prevent the bridging of the two MAC addresses in question to the other side. I would block those MAC addresses from being bridged primarily to prevent a (pseudo) multi master type of situation. Consider if you will if workstation A2 ARPs for the (shared) IP of workstation A1 / B1. Both workstation A1 and B1 will reply to the ARP saying IP is at MAC <bla>. So workstation A2 will have two ARP replies to deal with, thus being an IP conflict. Wh
ere as if you prevent workstation A1 and B1's MACs from being bridged, then both workstations will reply to the ARP, however the replies will not be bridged because they will be filtered out by source MAC. If you are wondering about the ARP reply form workstation B1 just broadcasting out in to the ether with the requester never actually talking to workstation B2, there is no real problem with this. Yes, it is wasted traffic, but there is no harm in it.
This bridging while filtering out the conflicting source MACs will allow all other equipment on the networks to communicate with out any problem.
Grant. . . .
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prev parent reply other threads:[~2006-07-08 21:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-08 21:14 [LARTC] Mulitple VLANs containing the same ip subnet NATed on same Geoff Karl
2006-07-08 21:39 ` [LARTC] Mulitple VLANs containing the same ip subnet NATed on Geoff Karl
2006-07-08 21:39 ` Grant Taylor
2006-07-08 21:49 ` Grant Taylor [this message]
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