5.2 Bridging issue
bjorn at eikeland.info
Thu Feb 12 06:32:21 PST 2004
På Thu, 12 Feb 2004 03:56:56 -0700 (MST), skrev Aaron D. Gifford
<agifford at infowest.com>:
> PROBLEM SUMMARY:
> I've got a bridge(4) issue on a BSD 5.2.1 box. The bridging box has
> three ethernet interfaces, two bridged together in a single cluster, and
> one connected to the internet. The box acts as a bridge for the two
> network segments, and as a router to the Internet (it's the default
> gateway). The problem is, only one of the bridged segments can
> communicate with the BSD box directly (and thus the Internet), even
> though the two segments can talk to each other just fine.
> NETWORK SET-UP:
> First, let me clue you in on my network set-up:
> FreeBSD 5.2 Box with 3 ethernet interfaces, em0, rl0, and rl1:
> [FreeBSD Box]
> | | |
> rl0 rl1 em0
> | | |
> | | +---To-Internal-Network-Segment-#1...
> | |
> | +---To-Internal-Network-Segment-#2..
> Interfaces rl1 and em0 are bridged:
> Since they ARE bridged and so are "on the same subnet", only em0 has
> an IP address:
> ifconfig em0 inet 10.10.10.1/16
> I don't see how or why one would need or could assign an IP on the
> same subnet to the other interface, rl1, unless it was handled like
> many alias addresses, as a /32 host address.
> Interface rl0 is the link to the Internet.
> Bridging for the most part seems to be working. Hosts on segment #1
> (via em0) are visible to hosts on segment #2 (connected via rl1). They
> can ping each other, get ARP address resolution, and pass IP traffic.
> All hosts use 10.10.10.1 as their default gateway to the Internet.
> Hosts on segment #1 can reach the Internet just fine.
> PROBLEM DETAILS:
> Hosts on segment #2 cannot seem to be able to communicate with the
> bridinging/routing FreeBSD box's own IP addresses, and since it is the
> default gateway, in turn they cannot reach the Internet. No layer 2
> traffic (ARP) reaches the FreeBSD box directly (the ARP table shows
> "incomplete" for all segment #2 addresses, even though ARP packets
> DO reach segment #1 just fine, passing transparently through the
> FreeBSD box. The BSD box just can't see stuff addressed directly to it.
> This is NOT a firewalling or NAT issue. This is exclusively a bridging
> issue. Firewalling/NAT occurse elsewhere.
> So since I'm a FreeBSD bridge(4) newbie, after scouring the man page,
> reading the Handbook's information, searching various mailing list
> I can't find anything useful that tells me if bridge's bdg_forward()
> how to handle traffic like this. Apparently it doesn't.
> So bridging is just fine if you want your BSD box hidden, transparent,
> invisible. But if you want it visible so it can act as a default gateway
> to all segments of a subnet that are bridged together, HOW DOES ONE DO
> I can't ifconfig the rl1 interface with an IP on the same subnet unless
> a /32, and that accomplishes nothing (the IP packets are addressed to the
> IP address assigned to em0). Bridging SHOULD just bridge, so traffic to
> the BSD box's em0 IP should come in on rl1 and be processed by the host.
> Somehow the bridging code knows the MAC addresses on the segment #2 side
> things (rl1), since it passes traffic between the two segments just fine.
> But the kernel's ARP table is totally ignorant. It can't find those
> REQUEST FOR HELP:
> Thanks in advance for all help, pointers, etc. If there's not a way to
> this, then this sounds like an issue that should be added to the BUGS
> of the bridge(4) man page.
> Aaron out.
> freebsd-questions at freebsd.org mailing list
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Try sysctl net.inet.ip.check_interface=0 - sounds like the same problem i
had with my
bridge a while back.
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