My organization is planning to become multihomed in the near future.
Currently we have redundant (router and physical path) links to a
single AS where we get our transit, and speak BGP to them using a
private ASN. This configuration has not been meeting our reliability
requirements, so we will be getting our own ASN from ARIN, and moving
from PA to PI IP space.
Our new provider will be used for backup purposes only. We would like
to minimize the monthly cost of this connection; to do this, we are
planning to use a VZ business FIOS connection with symmetrical
bandwidth to establish a GRE tunnel to a datacenter somewhere, and
bring up a BGP session over that tunnel. I'd like to know if there are
providers that offer such a service on a regular basis, and if so, if
anyone is doing this and has words of wisdom.
Thanks in advance.
The general way this works for a small shop is two transits - one cheap
provider who you move most of your bits over, and one more expensive but
reliable link. Prepend / localpref / whathaveyou to your hearts content
until pleased with your bandwidth bill, and when your cheap link toasts
you're all set.
What you're suggesting with the GRE over commodity links would *work*, but:
(a) By the time you convince a network that they should do this for you,
you're likely going to be out as much money as just brining up directly
connected transit and not pushing much traffic at them.
(b) You're using the GRE setup as your backup... over a setup thats about
100x less reliable than your primary link.
-Jack Carrozzo
Hi Robert,
I use a similar technique myself and it works reasonably well.
Servint.net was willing to do it for me and he.net gave me a quote as
well. Three pitfalls to watch out for:
1. A small portion of your traffic is going to wander in via the data
center link and down the GRE tunnel during normal operations. You can
tweak the announcement so that it isn't much, but it won't be zero
either.
2. Make sure you originate the network announcement from your physical
location, not from the data center. In other words, no "network
10.2.3.0 mask 255.255.255.0" in the "router bgp" section at the data
center. If the data center becomes disconnected from you, it should
drop the announcement.
3. You'll need a small block (/29) of PA addresses at the data center
to anchor the tunnel.
Regards,
Bill Herrin
My network spans a multicity geographic area using microwave radio
links. The point of the GRE tunnel is to allow me to establish a BGP
session to another AS using a consumer grade Internet connection
(cheap) over the public Internet. I don't want to build out additional
microwave paths to a new datacenter to become multihomed.
Just make sure you don't shoot yourself in the foot by telling the best route to the end of the tunnel is via the tunnel itself...
I use it too: http://www.avonsys.com/blogpost367 but because I have no other choice.
Did you mean routing *your* end of the tunnel to the tunnel itself, or
announcing to the entire world that The Internet was best reached via your
tunnel? I think we've seen spectacular failures in both modes...
Just make sure you don't shoot yourself in the foot by telling the best route to the end of the tunnel is via the tunnel itself...
Right, nail up a /32 static route for the remote gre tunnel endpoint on each side. That /32 is nailed up to the next hop that you want the gre tunnel to always traverse. If that next hop becomes unavailable, the tunnel will go down, which is what you want rather than the tunnel trying to come up across some other path it can find.