On Tue, 2002-12-03 at 10:52, sabat wrote:> I''ve seen a lot of info about running redundant routes to
different ISPs
> in the HOWTO and on this list. That surprises me, because I would expect
> that a more common situation would be redundant routes to the *same* ISP
> -- the typical HSRP + load balancing that so many of them run.
Most people like me are not doing things that way, because if all my
lines come from 1 ISP then if they have any problems, it will affect all
lines.
Therefore by having separate ISP''s, the idea is one could be down, and
the other would be up. Chances that both would be down at the same time.
Heck even in my case, were 2 of my ISPs are North of me and the third is
south of me. However since all three lines travel the same first two
miles, I am looking into replacing one with a high powered wireless
connection. So if there is a problem in the first couple miles I won''t
be affects.
Now with that said what you are trying to do should be way easier to do.
Some ISP offer channel bonding. If not then see if they run BGP, or
other protocols that will allow for the same IP''s to work regardless of
router. This is not an area I have a vast amount of knowledge in, but
have done some research into it.
> Here''s
> what I want to do:
>
>
> ============ ===========> ISP Router 1 ---- HSRP ---- ISP
Router 2
> ============ \ / ===========> | \ /
|
> | / \ |
> | / \ |
> ============ / \ ===========> My Router 1 -- heartbeat -- My
Router 2
> (Linux) (Linux)
> ============ ===========> |
|
> | |
> ============ ===========> fw 1
fw 2
>
>
> I''m thinking of running ECMP outgoing from the routers labeled
"My
> Router x" to the ISP routers. It''s also probable that
we''ll have the
> ISP''s routers sending us alternating (ECMP) packets on the
incoming
> side. Our routers would have heartbeat running so that a failure on
> either box would cause the surviving router to take over its IP and MAC
> (VRRP is not a possibility for reasons not worth mentioning).
>
> Two questions here:
>
> - In some docs, I see mention of using SNAT on outgoing packets to keep
> a connection hooked up with one router. That''s only necessary for
> multiple ISPs, right?
It will only be necessary if a certain router must respond using a
certain IP. So if ip1 is bound to rt1 then yes. If ip1 can travel via
both routers, then no.
I would not think it to be necessary in your case, but it may apply. If
I understand things correctly, NAT is mostly used to make sure packets
go out the way they came in, and are mapped to the correct IP for the
corresponding ISP. None of which applies in your case, unless each
router will respond to different IP''s. If they both share a pool of
IP''s, then you should not need it.
> - Is this going to be more trouble than it''s worth -- packet
re-ordering
> or some other unforeseen problems?
I do not think so, in your case you will more than likely be able to use
multiple lines as one physical line. Depending on how things are
configured. I would give it a try, but keep in mind all you will get is
increased bandwidth. I do not see you having any sort of redundancy.
That would require more than 1 ISP, and etc. in my opinion.
--
Sincerely,
William L. Thomson Jr.
Support Group
Obsidian-Studios Inc.
439 Amber Way
Petaluma, Ca. 94952
Phone 707.766.9509
Fax 707.766.8989
http://www.obsidian-studios.com
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