[NANOG] Multihoming for small frys?

Heather Schiller heather.schiller at verizonbusiness.com
Wed May 21 12:08:06 CDT 2008

William Herrin wrote:
> Hi folks,
> An administrative question about multihoming:
> I have a client who needs to multihome with multiple vendors for
> reliability purposes, currently in the Northern Virginia area and
> later on with a fail-over site, probably in Hawaii. They have only a
> very modest need for bandwidth and addresses (think: T1's and a few
> dozen servers) but they have to have BGP multihoming and can afford to
> pay for it.
> The last I heard, the way to make this happen was: Find a service
> provider with IP blocks available in ARIN's set of /8's that permit
> /24 announcements (networks 199, 204-207), buy a circuit and request a
> /24 for multihoming. Then buy circuits from other providers using that
> ISP's /24 and an AS# from ARIN.

Yes, but the order is wrong..

- Order service from 2 providers
- Request an ASN from ARIN, show them your documentation that you are 
getting service from 2 providers to justify your need for an ASN
- If you don't meet the utilization requirements for getting a /24, 
request a /24 for multihoming under ARIN from ONE of your 
providers (not both).

At UUnet/VZB we ask customers to provide their ASN as documentation that 
they have demonstrated their intent to multihome.

If you have existing IP space, and it's less than /24 don't be surprised 
if someone asks you to renumber.  If you have existing IP space /24 or 
larger, don't be surprised if someone turns you down under the 
multihoming policy.

http://www.arin.net/policy/nrpm.html#four236 Reassignments to multihomed downstream customers

Under normal circumstances an ISP is required to determine the prefix 
size of their reassignment to a downstream customer according to the 
guidelines set forth in RFC 2050. Specifically, a downstream customer 
justifies their reassignment by demonstrating they have an immediate 
requirement for 25% of the IP addresses being assigned, and that they 
have a plan to utilize 50% of their assignment within one year of its 
receipt. This policy allows a downstream customer's multihoming 
requirement to serve as justification for a /24 reassignment from their 
upstream ISP, regardless of host requirements. Downstream customers must 
provide contact information for all of their upstream providers to the 
ISP from whom they are requesting a /24. The ISP will then verify the 
customer's multihoming requirement and may assign the customer a /24, 
based on this policy. Customers may receive a /24 from only one of their 
upstream providers under this policy without providing additional 
justification. ISPs may demonstrate they have made an assignment to a 
downstream customer under this policy by supplying ARIN with the 
information they collected from the customer, as described above, or by 
identifying the AS number of the customer. This information may be 
requested by ARIN staff when reviewing an ISP's utilization during their 
request for additional IP addresses space.

> Is that still the way to make it happen? Are there alternate
> approaches (besides DNS games) that I should consider?
> Who should I talk to? Certain well-known companies seem incapable of
> discussing service that isn't cookie-cutter.

It's really pretty straightforward and common actually... but I wouldn't 
be surprised if sales folks don't know ARIN and/or routing policy.

> Thanks,
> Bill Herrin

  Heather Schiller
  Customer Security
  IP Address Management

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