[AusNOG] Multiple IP Transit BGP

[Matthew Maxwell]

The easier way is using BGP PfR to do this.

Without using PfR and smaller routers in the past I've used route servers
(running quagga or similar) having the routers as RR clients to the route
server and letting scripts on the RS handle the policy side of things.

As for memory usage, here be dragons!
If you run two full feeds into a VRF instead of global table you're looking
at over 4GB of RAM.

Sent from my iPhone.

On 26/04/2012, at 16:12, "Sean K. Finn" <sean.finn at ozservers.com.au> wrote:

Are you Inbound-Heavy or Outbound-Heavy?







For Inbound-Heavy..



I’ve seen it done where you run something  monitoring what your link to
trigger when you consider it ‘full’, such as Cacti with THRESHOLD module
with alerting turned on, or otherwise a timed event trigger to run, at,
lets say, 30 minutes before you regularly hit peak time.



e.g. a cron-job on a linux box somewhere, or a triggered script, SSHing /
(Or Telnetting) into a server, running an ‘expect’ script, and then running
the commands that will either ‘turn on’ bgp, or change your route maps.





The real fun will be in HOW you balance your traffic across these links.



I would be of a mind to run both as active-active, and to use route-maps in
all of their glory and configuration hell to try to balance your traffic as
best as possible.



If you have multiple /24’s you could preference some over one, and others
over the other, and shuffle them around until you approximate some sort of
balance,

Or,



On your least-preferential route, add an AS path prepend or two to make it
look like a longer path, and somehow achieve some sort of lucky balance.





Adding a second carrier is really where the fun begins, and, being the wild
internet, you really just have to come up with a configuration or two,
deploy, and suck-it-and-see.





For outbound-heavy traffic, you should start by profiling which AS’s you
send the most amount of traffic to, then, figure out which ones are
‘closest’ on the network to each of your two connections.



If your routers are big enough, you could take two default-routes via BGP
from both providers, AND two full-global or full-national routing tables.

Be careful with taking too many routes, if your routers don’t have enough
ram to hold it all BGP will die and you’ll just stop routing, period.



If you can take two full global tables, I’d suggest at least 2GB of ram
(Others on the list feel free to chip in at this point what’s enough ram),
then you can construct some route-maps to tag certain prefixes learnt from
certain networks with local-preferences, to push traffic out an appropriate
link.







In essence though, even if you turn on your second link when your first one
is maxing out, you’re still going to need route maps, one way or another,
to control which of your BGP neighbors see’s what.



Welcome to BGP Hell J

(Otherwise known as Job Security).



S.



*From:* ausnog-bounces at lists.ausnog.net [mailto:
ausnog-bounces at lists.ausnog.net] *On Behalf Of *James Mcintosh
*Sent:* Thursday, April 26, 2012 3:47 PM
*To:* ausnog at lists.ausnog.net
*Subject:* [AusNOG] Multiple IP Transit BGP



Hi Noggers,



We currently advertise our whole IP range via a single IP Transit upstream
carrier who supplies us 150Mbps of transit.



We are are adding another 70Mbps but from a different carrier.



I've Googled high and low but can't seem to find the answer and I'm
personally a bit rusty on my BGP. Really hoping some of the pro's on the
list can help.



How would we advertise make use of the the new 70Mbps IP transit but only
once the existing 150Mbps was full. As an overflow type of set up.



Is this even possible? Or are there better ways to manage multiple upstream
carriers?



I'm using a Cisco 7206 VXR.



Thanks and really appreciate the help...





-James
_______________________________________________
AusNOG mailing list
AusNOG at lists.ausnog.net
http://lists.ausnog.net/mailman/listinfo/ausnog
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ausnog.net/pipermail/ausnog/attachments/20120426/3de26efb/attachment.html>