Re: bridge with access on both interfaces

From: Robert Watson (rwatson_at_freebsd.org)
Date: 12/25/03

  • Next message: Michael Sierchio: "Re: bridge with access on both interfaces" 
    Date: Wed, 24 Dec 2003 18:44:22 -0500 (EST)
To: Ian Smith <smithi@nimnet.asn.au>

    On Wed, 24 Dec 2003, Ian Smith wrote:

    <snip>
    > What I can't get to is setting up both NICs for the same /24, using
    > either one or two separate addresses. I'd hoped to get away with one
    > IP, which some of the docs (and bridge.c, skimmed) led me to believe
    > that any local IPs of this host, on whatever of the bridged interfaces,
    > should provide unbridged local stack access - however if we need to have
    > 'inside' and 'outside' IPs separately on each bridge interface, fine.
    >
    > In short, ifconfig appears unwilling to have two NICs covering the same
    > /24. Can this be set up? I'm also at a bit of a loss with the routing,
    > so inside packets to the bridge box (ie unbridged packets) are responded
    > to on the same interface, and outside unbridged packets go only to/from
    > the gw. Some tcpdumps on both in and outside interfaces suggest an ARP
    > response problem also, perhaps; no responses on the inside iface at all.
    >
    > I'm unsure if that's too little initial detail or too much?
    <snip>

    If you want to use IP while bridging, you'll typically want to configure
    IP on one of the interfaces making up the bridge, and then simply
    "ifconfig up" the remaining interfaces without explicitly configuring IP
    on them. If you get ARP warnings, you can silence them using a sysctl (I
    can't remember if I got them last time I did this, however).

    At one point I rewrote bits of our bridge code to create virtual bridge
    interfaces, the idea being that you'd configure IP on the virtual
    interface rather than on one of the member interfaces. However, I never
    got around to merging those changes -- my real goal was to allow sniffing
    of packets to/from the host on any component interface, and BPF only
    picked up packets from/to a specific interface (or leaked bridge packets
    for unknown target addresses). I'm sure at some point, someone will get
    to reimplementing our bridge code to take this approach, however.

    Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
    robert@fledge.watson.org Senior Research Scientist, McAfee Research

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  • Next message: Michael Sierchio: "Re: bridge with access on both interfaces"

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