I discussed fault tolerance a lot before with customers who has a web site
that would like to be up all the time using DSL lines. As far as I can tell,
there is just no easy way to achieve a high-level of fault tolerance without
running some kind of dynamic routing protocols with your ISP.
Your idea of using two DNS servers won't work. When anyone tries to send an
email, their smtp server will randomly pick one of the authorized name
server requesting for your IP address. Therefore, you would still have 50%
chance of failure if one of the DSL is down. I would recommend that you get
some kind of load balancing device in front of these two DSL lines. Or, if
mail is all we are concerned about, you could assign one IP from ISP A as
the primary MX record while use IP from ISP B as a backup MX record. That
will make sure your mail always get to the exchange server.
BTW, I would not recommend using a second DSL line to backup another DSL
line since both DSLs would probably go into the same DSLAM in the same CO
anyway...
Richard
""Steven V. Snead"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Load balancing would be nice but my real goal would be to have Fault
> tolerance on my NT 4.0 box. Fault tolerance between the two DSL
> connections, such that if one DSL fails, it will switch over to the other
> DSL, so that the exchange server still receive mail. My thought was to
use
> two DNS servers the primary pointing to one IP and the secondary pointing
to
> another IP from the other DSL circuit. I'm a little lost on how that can
be
> set up on the server end. Two NIC cards ? I guess I need hardware but
would
> like to do it without NAT. I can't believe this is something that can't be
> done and hopefully without BGP because working with the ISP seems
impossible
> for this to happen.
>
> Thanks,
>
> Steven V. Snead, MCSE, MCP+I, CCNA
> [EMAIL PROTECTED]
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