For BGP Longest Match Prefix always wins, no amount of prepending will beat that (they can of course filter it out etc)
There are a few ways you could do this: 1. Advertise the 48.0/20 out of both providers and then advertise a /22 (or other longer prefixes) out of selected providers. Then anyone who receives both will get the /22 as preference over the /20 (no prepending required) 2. advertise just the /20 out of each upstream and prepend so that popular networks get the same path length for both (look at the later on tie breakers) as some upstreams have more internal AS’s that you may pass through than others so it can be good to balance up the AS Path lengths to some popular spots (help to balance out the load a little) - you would need to prepend different amounts and then test them. I have done some similar parts of this on my network. Regards Alexander Alexander Neilson Neilson Productions Limited [email protected] 021 329 681 022 456 2326 On 26/08/2014, at 3:42 pm, Terri Kelley <[email protected]> wrote: > Don't think that would work quite right. Still want the others to come in on > TW if they want to. > > Terri Kelley > Network Engineer > 254-697-6710 > Farm to Market Broadband > > > > On Aug 25, 2014, at 10:32 PM, Alexandre J. Correa (Onda) wrote: > >> Just announce 52.0/22 to TW .. and this 'win' :) >> >> >> On 26/08/2014 00:07, Terri Kelley wrote: >>> I think I asked this before but can't find it so here it is. I coming up on >>> the need to load balance between my upstreams from my bgp edge. Question >>> is, do I have to list each subnet prepending the ones I want or can I list >>> the whole subnet then follow that with the prepend on the part that I want. >>> Example is (changing the real IP blocks for the example) with TW being one >>> of my upstreams and ATT the other all to the same edge router… >>> >>> /routing filter >>> add action=accept chain=TW-out prefix=192.168.48.0/20 >>> add action=discard chain=TW-out >>> add action=accept chain=ATT-out prefix=192.168.48.0/20 >>> add action=accept chain=ATT-out prefix=192.168.52.0/22 set-bgp-prepend=3 >>> add action=discard chain=ATT-out >>> >>> I'm hoping that will move the 192.168.52.0/22 over to the TW side unless it >>> goes down and leave the rest of the 48.0/20 block on the ATT. Otherwise I >>> need to list each one subnet out on the ATT entries I think. >>> >>> Terri Kelley >>> Network Engineer >>> 254-697-6710 >>> Farm to Market Broadband >>> >>> >>> >>> -------------- next part -------------- >>> An HTML attachment was scrubbed... >>> URL: >>> <http://mail.butchevans.com/pipermail/mikrotik/attachments/20140825/7723f8d3/attachment.html> >>> _______________________________________________ >>> Mikrotik mailing list >>> [email protected] >>> http://mail.butchevans.com/mailman/listinfo/mikrotik >>> >>> Visit http://blog.butchevans.com/ for tutorials related to Mikrotik RouterOS >>> >> >> _______________________________________________ >> Mikrotik mailing list >> [email protected] >> http://mail.butchevans.com/mailman/listinfo/mikrotik >> >> Visit http://blog.butchevans.com/ for tutorials related to Mikrotik RouterOS > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://mail.butchevans.com/pipermail/mikrotik/attachments/20140825/715b0c7b/attachment.html> > _______________________________________________ > Mikrotik mailing list > [email protected] > http://mail.butchevans.com/mailman/listinfo/mikrotik > > Visit http://blog.butchevans.com/ for tutorials related to Mikrotik RouterOS _______________________________________________ Mikrotik mailing list [email protected] http://mail.butchevans.com/mailman/listinfo/mikrotik Visit http://blog.butchevans.com/ for tutorials related to Mikrotik RouterOS
