[c-nsp] Basic inbound BGP path preferencing query

[Brian Turnbow]

Hi Josh

You can also check if your upstreams provide some communities to help in this case.
Some allow setting communities on your announcements that create prepends, from global prepends to more specific prepends ( i.e set a prepend for all peers at linx)

For example as174  has this document that describes the communities they have that you can use and what they do.
http://cogentco.com/files/docs/customer_service/guide/global_cogent_customer_user_guide.pdf


Best Regards

Brian


> -----Original Message-----
> From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Joshua Riesenweber
> Sent: martedì 27 gennaio 2015 23:15
> To: Steve Housego; cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Basic inbound BGP path preferencing query
> 
> Hi all,
> Thanks for all the replies, I had a feeling that with a single /24 there would be
> very little I could do.
> I had a  read through this doco, which described the scenario I'm talking
> about.http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-
> protocol-bgp/13762-40.html#conf5
> 
> They also suggest the way to do it is with AS-path prepend, but in the
> example they use x2 /24 subnets.
> I will look into a /23 and try my luck.
> 
> 
> Cheers,Josh
> 
> 
> > From: Steve.Housego at itps.co.uk
> > To: joshua.riesenweber at outlook.com; cisco-nsp at puck.nether.net
> > Subject: Re: [c-nsp] Basic inbound BGP path preferencing query
> > Date: Tue, 27 Jan 2015 14:52:04 +0000
> >
> > You could always use an as-path prepend,
> >
> > Announce yours routes with the same prefix from both connections
> >
> > route 1 would show as AS123 AS5089 AS-XX route 2 would show as AS123
> > AS123 AS174 AS-XX
> >
> > This allows more traffic to come in via route 1, whilst still
> > utilising route 2, (you can also add multiple pre-prends if required).
> > For example
> > AS174 will prefer customer routes so traffic from as174 to your as123
> > should always come in that path. Any of AS174¹s peerings may prefer
> > that route if they don¹t also peer with AS5089 for example.
> >
> > This obviously only works per entire subnet rather than individual
> > IP¹s but it still allows you to utilise both links un-equally (if
> > that¹s a word? :).
> >
> > SteveH
> >
> >
> > -----Original Message-----
> > From: Joshua Riesenweber <joshua.riesenweber at outlook.com>
> > Reply-To: "joshua.riesenweber at outlook.com"
> > <joshua.riesenweber at outlook.com>
> > Date: Tuesday, 27 January 2015 01:28
> > To: "cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net>
> > Subject: [c-nsp] Basic inbound BGP path preferencing query
> > Resent-From: Steve Housego <Steve.Housego at it-ps.com>
> >
> > >Hi all,
> > >I'm looking for a bit of insight from someone with more BGP
> > >experience than me. (I've tried searching around the 'net trying to
> > >find an elegant
> > >solution.)
> > >I have the common enterprise configuration of 2x WAN links
> > >multi-homed with 2x ISPs. I have a single /24 public IP allocation
> > >being advertised out both links, and are using MEDs  to preference one
> link.
> > >I'd like to load balance across both links, unfortunately, one link
> > >is lower-bandwidth and has a smaller data quota from the ISP.One
> > >simple solution is upgrading to a /23. Then I can preference a unique
> > >/24 subnet over each link, and assign the large bandwidth-consuming
> > >devices to that particular subnet on my better WAN link.
> > >My only hesitation is that configuration potentially uses more IP
> > >addresses than I need. Does anyone have any tips on preferencing
> > >certain IP addresses inbound through one link if I am only
> > >advertising a single /24?
> > >If there's a better way of doing this your ideas are welcome.
> > >
> > >Cheers,Josh
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