On 11/2/2007 11:35 PM, Corey Hickey wrote:
I meant to do both, which I think is necessary in order to make the
OPs proposed scheme work without modification. I'll defer if I'm
wrong, though--I haven't tested it, and, as you said in your other
email, it's "a very weird scenario."
As long as there are routes in both directions there should be no need
for SNATing.
I don't think this will work unless BR has a route like:
# ip route add 192.168.4.0/24 via 10.3.0.13 dev eth0
...whereas the OP only specified wanting routes to a few specific
machines rather than the whole networks.
In any case, debating that is probably academic, since I agree with
you in principle. It should be cleaner to set up routes for the whole
networks and use iptables rules on A1 to only allow traffic to/from
specified hosts.
Agreed. I mis read the routes on the two routers AR and BR to be for
the entire networks. Though again presuming there are routes, things
should work. This is more just a semantical mis-interpretation on the
scope of what the routes are for.
There are certainly different ways to do it, and I furthermore agree
with you that using a separate link between AR and BR (as you
suggested in your earlier message) is cleaner still.
I prefer bridging in this situation mostly because it distributes
traffic and reduces the load on the routers.
I can see how this would reduce load on the routes, but I don't believe
that load on routers will be much of a concern. (At least the routers
that I use (pick any box (less than 10 years old) and install Linux)
would do just fine.
However I would be concerned about broadcast storms being propagated
across the bridge unnecessarily. But if steps are taken to mitigate
that then it is probably not that big of an issue.
The two networks in question are rather small and occupy adjoining
buildings. Network A had to be rebuilt after getting torn out while
the corresponding building underwent a very intrusive retrofit and
remodeling. Prior to that, the two networks were bridged and shared
the same subnet. I don't know if the OP has a reason to isolate them
from each other now.
Ok... Obviously you are probably in a very unique position knowing the
history of the network.
I guess I'll go ahead and describe the former setup in a little
detail.
Every host in the entire bridged network was given an IP address
within the subnet 10.0.0.0/8. The bridge was configured to drop all
DHCP packets, so there was a DHCP server on network A and another on
network B.
Ok...
Hosts on network A were given addresses in the following ranges[1]:
10.0.0.0/16
10.1.0.0/16
10.2.0.0/16
Hosts on network B were given addresses in the following range:
10.3.0.0/16
...but, regardless of which network a host was on, it still was given
the /8 subnet, so hosts could communicate over the bridge without any
further configuration.
Ok, you chose to do in bridging what most people do in routing. Seeing
as how things were bridged you had to put things in place to stop things
that would naturally leave the subnet. Your preference to have and work
with.
Since each network had its own router to the Internet, the DHCP
servers also specified separate gateways. The bridge was configured
to drop packets with sources or destinations that didn't match the IP
ranges corresponding to the source/destination networks[2].
Ok...
That's all.
So let me get this right, you did bridging rather than routing to avoid
load on the router(s)? Yet you had to put more load on the bridging
host to segregate the networks like they would be if they were routed
while still allowing host to host communications between the two buildings?
<personal opinion> Strange </personal opinion>
My philosophy was to allow unrestricted communication over the bridge
and gently LART users that caused trouble (always inadvertently;
Windows worms and such). If the OP wants to allow communication only
to a few hosts, that's no more difficult--just write a few rules to
accept desired traffic and then drop/reject the rest.
Ok.
[1] Given the chance to do it over, I would have allocated addresses
to network A from 10.0.0.0/18 and network B from 10.4.0.0/18 in order
to simplify a little bit. Also, I should mention that the use of
several /16 ranges doesn't mean we had anywhere near that many hosts;
the separation was just for management.
*nod*
[2] Just in case some users on network B tried to manually set their
IP address and gateway in order to use the better Internet access of
network A. Of course, they could still have tunneled through the
bridge to an accomplice on network A, but they could have also used
an accomplice's wireless router, or CAT-5 strung between rooftops, or
RFC 1149, etc. I dealt with such things on a case-by-case basis. :)
That's what a "Clue-by-4" is used for. ;)
All in all you chose to implement a solution in one way that very like
did exactly what you needed even if it was a bit different than what the
industry norm would have been. Either way, bridging or routing, they
both would have / do / will work.
Grant. . . .
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