Disaster recovery using as-prepend?

Ejay Hire ejay.hire at isdn.net
Thu Feb 16 18:00:34 UTC 2006


Answering the original question, as prepends are not a 
definitive way  to force all traffic to one site or the 

Two ways that definitely will work are.

1.  Send a community to the upstream provider at the 
backup site that causes them to set a lower plocalpref on 
the route you send them vs. the route learned from the 

2. If you have a large enough ip block, Advertise an 
aggregate address from your backup site, and more 
specifics from your primary.  I.e. advertise a /23 from 
your backup site and the same /23 as two /24's from the 


Thu, 16 Feb 2006 16:10:02 +0100
  Florian Weimer <fw at deneb.enyo.de> wrote:
> * Christopher J. Pilkington:
>> We have a disaster recovery site which will have a clone 
>>of the myriad
>> production servers.  We'd like to fail over to that site
>> automagically.
>> I'm thinking advertising the same prefix and just doing 
>> as-prepends.  However, now I'm not sure if this is a 
>>polite thing to
>> do or not.
> Can your backup servers run in parallel to your primary 
>servers?  How
> do you handle conflicting updates (assuming that the 
>services are not
> completely stateless)?

More information about the NANOG mailing list