BGP for disaster recovery site
Scott Weeks
surfer at mauigateway.com
Mon Sep 29 20:49:22 UTC 2008
Inline...
--- CHRISTINE.M.BERNS at sargentlundy.com wrote:
We currently have a routable block (class B) of IP
addresses. We are in the process of designing a
disaster recovery site. Our main site is already
dual homed to two different Internet service
providers via BGP.
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First, unless the first two bits of the first octet are "10" it's not a "Class B". It's a /16, which is the same size as a "Class B" but the first two bits of the first octet are not necessarily "10".
Are these two sites (main and DR) in the same ASN?
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A consultant told us that in order to allow us to
test access to the DR site without affecting the
production environment, we should get another block
of addresses from ARIN and advertise those addresses
out the DR site's Internet connection. Can we even
expect to get another block from ARIN if we already
have a class B...
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I would consider another consultant if you have not used 80% of your current allocation. ARIN will not allocate anymore space until you hit 80% utilization
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...and could we not accomplish the same thing by
advertising a subnet of our existing Class B at the
DR site? I would actually prefer to advertise a
subnet of our class B, but am wondering if there
are any reasons why this is not a good idea.
-------------------------------------------------
If the two sites are not in the same AS it's not a good idea unless you're experienced with such things. See past posts in the archives about the subject.
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Also, I have seen reference to some Internet service
providers possibly not accepting /24 BGP routes and
either dropping them or aggregating them to a /21
or /20 or /19. Are there recommendations as to
what is the longest prefix that we should advertise
to guarantee that the prefix will be advertised
throughout the Internet?
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Nothing is ever guaranteed WRT routing certain prefix sizes on the internet, but you should have no problems with a /24. Any longer (a /25) and you will not have good connectivity on the internet.
scott
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