Harry,
There is a Cisco mailing list called Groupstudy. The members there are
studying for various cisco related certifications. They might welcome your
question as a case study. Feel free to join, and post it there.
I do have some comments.
You might want to consider connecting to PSINET at two geographically
different pops. That will get rid of your latency problem if it is due to
traffic at the pop you're connected to or if you have a bottleneck at your
serial link (T-1?). It would also relieve you of the burden of carrying full
BGP routes. As a side effect, you might also get protected from the
"backhoe" problem. (If you choose this, use different carriers for the T-1s
if that will bring the data in on physically different wires.)
If that isn't the case, you can connect to two different ISPs, e.g, PSINET
and UUNET. The first problem you face is that the ip address you were
assigned (unless you got it from ARIN) belongs to PSINET. They simply gave
you a small portion of their total address space. The BGP tables point all
traffic for a large range of addresses (via a single routing table entry) to
PSINET. Once delivered to them, PSINET figures out which customer to send
which traffic to. You also have an Autonomous System number (AS), probably
also assigned by PSINET. AS numbers are in the range of 1 to 64K. The top 1K
are public (same as the 10.0/8, etc nets). PSINET has several numbers in the
first 63K, and uses each one of them to collect traffic for 1K customers. To
multi-home, you'll need your own, registered AS number, too. In addition, if
you multi-home, you'll need border routers with the capability to handle
full BGP tables (lots of money/memory).
Extending your reach to two ISPs is technically possible, but somewhat
complex. You'll pay for that complexity in both dollars and time. Make sure
that the problem is really big enough to warrant the solution.
Steve
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Harry Whitehouse
Sent: Tuesday, May 30, 2000 7:03 PM
To: [EMAIL PROTECTED]
Subject: OT: Multiple ISP's
Please excuse this off-topic question (and feel free to recommend any better
suited lists).
My firm has a single ISP (PSINET) and reliability has been reasonable over
the years using their T1 service. But we have periods where customers can't
ping us, or their tracerts show severe latency problems -- perhaps once a
week. Often we "lose" an entire geographic segment for several hours.
So I'm looking at adding a distinct, redundant ISP. But I'm uncertain how
this works.
All my remote clients will be pointing to www.xyz.com. That will resolve to
a single IP address, correct? But then how can one use multiple ISP's? I
know this can be done, I just would like to understand how. An suppose one
ISP's route is blocked, how does the client know to switch over to the other
route?
Also, any suggestions on the hardware needed to pull this off on the "my"
side would be appreciated. I've seen stuff like www.FatPipeInc.com which
seems to address this issue.
TIA
Harry
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