[c-nsp] Need some advice on ISP failover for an enterprise

[Andrew Gabriel]

Hi,

We have servers at two of our large locations in a single country that need
to be reached from the Internet. Both locations each have a single 45 M ISP
link, and also have internal connectivity with each other through multiple
private links. The private WAN connecting the two locations has plenty of
bandwidth and the latency is less than 40 ms between the two sites.

We have our own registered ASN and public IP ranges. We have multi-homed ISP
links at several other locations but not at these two locations. Also, both
locations are partly ready for multi-homing in that they already use our own
IP range and run BGP to the provider using our ASN.

We have been asked to implement failover, for both the locations. The
options we are considering are:

   1. Traditional multi-homing  by adding a second ISP at each location.
   2. Buying a leased line to connect the CER at both locations and letting
   the incoming traffic for either location transit over that line to provide
   failover when one site's ISP goes down. This link would terminate on the
   'dirty' side of our firewall and not have anything to do with the internal
   WAN.
   3. Setting up a VPN-type tunnel between the ISP routers at both sites
   that would be routed over our internal WAN. This is similar to option 2 but
   doesn't involve any extra cost.

Obviously we would prefer option 1 as it is simplest and safest to set up,
and we already have experience with that type of setup, however we have been
asked to look at cheaper options due to budget constaints, hence wanted some
advice on the other options, do you think they could work well, any
potential issues we should look out for, or should we even be considering
them?

Regards,
Andrew Gabriel.
Network Engineer,
Enterprise Data Services.
+91 44 42 22 88 75 (Direct)
+91 98 41 41 40 19 (Mobile)
www.sanmina-sci.com
Sanmina-SCI India Pvt. Ltd.
A51, 2nd Avenue, Anna Nagar,
Chennai - 600 102, INDIA.

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