On Fri, Jul 07, 2006 at 10:56:11AM -0500, Jacob Yocom-Piatt wrote:
> already have available (the 2 ADSL connections + old hw).
>
> i think CARPing machines when they're in different public IP blocks won't
> work,
> i.e. x.y.z.w/29 and a.b.c.d/29 cannot have a single address CARPed across
> blocks. do tell if i'm wrong on this one since this would work nicely for the
> situation i've described.
>
> cheers,
> jake
I think you can do it with the following: Get 2 cheap routers that can pass
3Mb/s, no big functionality needed except that they do ethernet (Cisco 2500's?
they should be cheap by now..), 2 switches for the etherlink between the two
locations (if a direct ethernet link can't be established perhaps use an
OpenBSD bridge with ethernet over gif(4)?) and then the existing routers
configured with carp. In ascii it would look like so:
0.0.0.0/0 (cloud)
|
+--------------+----------------+
| |
| ADSL 1 | ADSL 2
+---+ +---+
| | CARP | |
+---+ +---+
| |
| 192.168.0.0/24 |
+-------{ ethernet (gif) }------+
| |
| |
+---+ +---+
| | Cisco 2500 | | Cisco 2500
+---+ +---+
| |
| |
x.y.z.w/29 a.b.c.d/29
With this setup you can ensure that OUTGOING ip packets make their destination
on a redundant setup, provided the ADSL links do not filter egress traffic,
which they might (worth checking). For INCOMING traffic to both x.y.z.w/29 and
a.b.c.d/29 to work the upstream ISP must have similar failover on their end to
re-route traffic into the "ADSL 2" router if "ADSL 1" link is detected as down.
This may be harder to set up, but maybe it is not.
If you're wondering why the RFC1918 address within the switch, don't worry
about it. Those IP's aren't expected to talk to anything anyhow they just
route. @HOME used to do it years ago, and people bitched but they got over
it. Just filter any packets with a TTL of 1 and noone will know either way,
except that traceroute has a small pause on that hop.
regards,
-peter
--
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