You can just accept directly-connected peers from each network (or within 2 AS's, etc) then point a default at each one with different preferences. You can do with with two edges if you like also: iBGP between the edges, and push default into OSPF from both.
WRT dynamic load balancing... generally if your network is large enough for two upstreams you'll have a pretty good distribution of flows so once you get the prefs and prepends setup the way you like, thing won't shift that rapidly. In my experience at least... -Jack Carrozzo On Tue, Jan 18, 2011 at 1:32 PM, Ahmed Yousuf <ayousuf0...@gmail.com> wrote: > Hi, > > > > I'm looking at a setup where we use BGP to announce PI space to two > upstream > ISPs. ISP A provides a 30Mb/s connection and ISP B provides a 10Mb/s. > Originally the plan was to use ISP B's link as a backup and local pref > traffic outbound via ISP A and pref inbound using AS prepend via ISP A. > It > has now been requested to be able to distribute traffic across both links > rather than preference traffic to the higher speed link. We are going to > be > using Juniper SRX210s to do this. I have some questions: > > > > - Is this really a good idea, as the BGP process won't care what > the utilisation of the links are and you will see situations where the > lower > speed link gets used even though the high speed link utilisation is 0? > > > > - If we are doing this, I don't want to take a full routing table, > I would rather just take the ISPs routes and perhaps their connected > customers. One ISP has said they will only provide full routing table or > default. I really don't want to take a full table, is receiving default > only going to be a problem for my setup? > > > > - Any advice on how to avoid situations where the low bandwidth > link is being used even though there is 0 utilisation on the high bandwidth > link? > > > > Thanks > > > > Ahmed > >