Daniel,
We've done something very similar to this by putting active/standby load
balancing devices in an ISP. Your URL then points to a VIP on the load
balancing device. The device then health checks your two sites and load
balances accordingly.
If the ISP dies then, yes you'll lose both sites, but the world is a single
point of failure.
I've not mentioned the device above, but there are various solutions
including Foundry, Cisco CSS11000 and probably a fair few more.
I believe the problem with the DNS solution is that although a DNS TTL can
be set to 0, there is only a requirement to support TTL down to 2 days. So
DNS info can be cached for this period by non-authorative DNS'.
I think there is also a problem with browsers, which can also cache DNS info
for a period of time (40 minutes rings a bell but I don't know why).
DNS seems a lovely way of doing it, and the CSS11000 seems to do it better
than some other devices I've seen, not least because it can be the
authoritive DNS itself, but I don't know if there is a way round these
caching problems.
Can any DNS guru's out there throw some ideas in?
Gaz
""Daniel Wilson"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> The quick responses on this group are great! Thanks for the help so far.
>
> The content is not static. The sites in question run e-commerce. We
could
> look at
> setting up access from both servers to the same DB server over an internal
> network ...
> so that would answer that objection to the solution you offered.
>
> I started by asking questions on a different group about round-robin DNS.
> What I was
> told was that since we don't control anyone else's DNS caching settings
(our
> TTL entries
> etc. are really only suggestions) that when one T1 goes down & we change
the
> DNS
> settings to point to only the other line clients & other DNS servers would
> still try to
> access the downed T1. Is this accurate as far as you know? If round
robin
> DNS will
> provide fault-tolerance, that's great. If not ... we need to look
elsewhere.
>
> Thanks!
>
> --
> Daniel Wilson, BSCS, MCP
> Application Developer
> http://www.compusoftsolutions.com/
>
> Vijay Ramcharan wrote:
>
> > I believe what you're looking for is a way to load balance traffic to
> > your web servers. You also wish to achieve a degree of fault tolerance
> > in case one server goes down. If both servers have the same content and
> > the content is static, you could use a feature called DNS round-robin
> > which basically returns a list of IP addresses to a querying client for
> > any single hostname. If one server becomes unavailable the client can
> > use the other IP addresses given by the DNS server to access the same
> > site. There's no routing protocol involved here and I don't think it's
> > possible to do what you need using a routing protocol. The good thing
> > about DNS round-robin is that the IP addresses of the web servers could
> > be totally unrelated.
> > This seems to be more of an application specific need for fault
> > tolerance. If this is possible using a routing protocol I'd be happy if
> > someone pointed out the error of my ways. I'm always open to
> > suggestions.
> >
> > Vijay Ramcharan
> >
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
> > Daniel Wilson
> > Sent: Thursday, June 07, 2001 9:39 AM
> > To: [EMAIL PROTECTED]
> > Subject: BGP for 2 T1's to one LAN [7:7511]
> >
> > We are trying to have the web servers in our LAN accessible to the
> > internet via 2 T1's from different providers -- more for redundancy than
> >
> > load sharing, though that matters too. Currently we have 2 T1's, each
> > giving us a different set of IP addresses. That just lets us put some
> > sites on each T1 -- doesn't give us an ounce of redundancy.
> >
> > I've been told that if we get a router with 2 WIC's that can speak BGP
> > (Cisco 2600 or better) that may solve our problem. I'm very new to
> > routing, so can someone answer some basic questions?
> >
> > Is the idea with this solution that we will be running just one set of
> > IP addresses? And that, because of BGP on our router, either ISP will
> > be able to route traffic to that set of IPs on the T1 it provides?
> >
> > Thanks in advance.
> >
> > --
> > Daniel Wilson, BSCS, MCP
> > Application Developer
> > http://www.compusoftsolutions.com/
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=7531&t=7511
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