Gary Lawrence Murphy wrote:
>
> I hope you don't mind very naiive questions about bridging, but this
> is all very new to me and I'm wondering if I am heading in a wrong
> direction for what I want to do.
>
> We have a 486 machine on our network which currently hosts our
> intranet server (khttpd) and is also our printer server. I have
> recently added an adhoc wireless network interface and I'd like a
> transparent binding of the two networks to allow unrestricted network
> traffic in both directions (using IP Forwarding would restrict traffic
> back out to the wireless nodes).
Well, you could make a separate subnet for the wireless LAN and then use
your machine as a router. I'm pretty sure that is faster than using a
bridge, and since your machine is already loaded down, it might not be a
bad idea.
As a comparison, I just setup a 486DX2/66 w/ 16Meg RAM as a bridge using
netfilter (without any rules). The machine is basically unresponsive
when I push about 3.2Mbits/sec through it. If your running an older
1Mbit wireless network, that's gonna eat up 30% CPU right there. You
might get better performance than I did, though, because I installed the
netfilter patch so that I could do filtering too.
>
> Is this possible with the bridging tools?
Yes, but you might not want to.
>
> My reading of the Bridging HOWTO suggests that the bridge machine
> vanishes from the network, ie, I'd no longer have any access to that
> machine as an intranet server or printer server, but then again,
> assigning an IP to the bridge suggests that it might work.
Long answer:
Bridges are completely transparent. They listen on their ethernet
interfaces and build a table of which ethernet cards (by MAC address)
are on which ports.
Then, whenever they hear a packet for a give machine, they forward it
only to the port the destination card is connected to. This makes it
impossible to detect that you're not on one big ethernet segment (ie
connected together only by hubs), but shields you from traffic that
isn't yours, freeing up more bandwidth for you.
This bridging process happens completely independent of TCP/IP. That is
why you don't need to assign IP addresses to the ethernet interfaces.
But, if you want the machine to have an IP address, you can assign one
to the bridge as a whole. The biggest problem with a bridge is that
broadcast traffic must be forwarded to every port on the bridge because
any machine could want it. So if you have a busy 10Mbit network with,
say 100kbit/s worth of broadcast traffic and you bridge it to a 1Mbit
wireless network, you'll automatically eat up 10% of your wireless
bandwidth. But if your subnets are small (<100 hosts), you'll probably
be fine.
>
> I've read the Network and Ethernet HOWTOs, but have to confess that I
> really don't understand the fine details of networking. What has me
> especially confused is setting all interface net addrs to 0, and then
> (optionally) giving the bridge a new IP. Where I'm not clear is on
> the choice of IP for that bridge.
>
> 1) is the bridge IP on a new subnet? ie, if I am bridging
> 192.168.70.0 and 192.168.10.0, does that mean the bridge
> itself should not be either 10 or 70?
No, no TCP/IP routing takes place on a bridge, both sides are on the
same subnet. Give one IP to the bridge as a whole. If you want to have
two differnet subnet (.10 and .70), you'll want a router.
>
> My guess is that it might be possible to have the bridge on
> the ethernet subnet, on the 70.0 network. Would this mean it
> would be accessible to the ethernet side (for HTTP, ssh &c)?
> If this is true, then how do the wireless nodes see this IP?
> (default gateway?)
>
> if the bridge is on a new subnet, how do I set the routing
> tables on other machines to recognize this as the gateway to
> the other network?
>
> do I perhaps misunderstand "subnet" and need to assign an IP
> within 70.0 and then assign the wireless network as some IP
> range under the 70.0 network?
>
> 2) if my wireless beacon is now this new IP, can I still do
> dhcrelay from the server across to the wireless network?
If you bridge the two networks, you won't need any dhcp relay since
they'll be on the same logical ethernet segment (but different physical
ones).
>
> 3) would our intranet be accessible from both sides? If
> Do _all_ other stations in the ethernet network will need
> routing tables to include this new subnet as the gateway to
> the other (ie wireless) network and vice versa?
If you correctly configure either routing or bridging, both sides will
have full access each other.
>
> I follow the Bridging HOWTO so far as running brctl to create bridges,
> but I don't think I really understand how the bridge is used.
>
> For example, if I route through the gateway for the alternate subnet,
> does this mean I can access any of those machines by their respective
> IP?
>
> If I am on the wireless network and request an internet address, will
> the packets follow the default route to the bridge and from there
> follow the default route to our internet gateway on the 70.0 subnet?
>
> If you know any good references for rank beginner tutorials, please
> send them along.
>
> Again, my apologies for the naiive questions; if you have an
> opportunity to reply, your help will be greatly appreciated.
>
> --
> Gary Lawrence Murphy <[EMAIL PROTECTED]> TeleDynamics Communications Inc
> Business Innovations Through Open Source Systems: http://www.teledyn.com
> "Computers are useless. They can only give you answers."(Pablo Picasso)
>
> _______________________________________________
> Bridge mailing list
> [EMAIL PROTECTED]
> http://www.math.leidenuniv.nl/mailman/listinfo/bridge
Hope that helps!
Logan Bowers
_______________________________________________
Bridge mailing list
[EMAIL PROTECTED]
http://www.math.leidenuniv.nl/mailman/listinfo/bridge
