I understand the what sync does and I also assume that someone setting up such an config, dual homed full routing, should understand BGP fundamentals. It's like auto summerization, I have never seen it fix anything but I have seen it cause problems many times.
Dave Jay wrote: > > It's not default for the same reason why unicast rpf (antispoofing) is > not default in ISO; because people are stupid, and under poor design, it > could produce very undesirable and hard to troubleshoot results. In > other words, if you don't know why you are disabling synchronization, > don't do it. > > Take the following scenario: A multihop iBGP link between routers (A) > and (B) in which a non-bgp IGP router (C) is routing packets between > them. Both BGP links are advertising full tables to each other, and, > under your suggested default config, would attempt to forward packets to > destinations that router C has no clue about. Then what does router C > do with these destinations? > > The answer, of course, is to set up a iBGP full mesh, and then to > disable synchronization , and if you are smart, design your network so > that your IGP learns only about downstream routes and set a default > route up to the core of your network. > > Anyway, the point being, sync is enabled by default because you really > should know what you are doing before you disable it. > > On Mon, 2002-04-08 at 10:44, MADMAN wrote: > > I can think one one good reason why you would disable sync, you can't > > redistribute 100K routes into ANY IGP. Why are you so concerned about > > disabling sync?? It should be default. > > > > Dave > > > > Jay wrote: > > > > > > BGP Rules of thumb: > > > > > > BGP advertised prefix must also exist in local IGP table. > > > iBGP learned prefix must also exist in local IGP table > > > -or use #no sync on iBGP learning router, but if you do, you'd sure as > > > hell better know why you disabled it. > > > > > > On Sun, 2002-04-07 at 09:22, Phil Barker wrote: > > > > Hi Group, > > > > > > > > Hope someone can help out with this as I don4t have > > > > access to my kit at the moment. > > > > > > > > I tried to set up my first BGP lab last week. > > > > I configured a full iBGP mesh, three routers connected > > > > in a triangle via serial lines. > > > > > > > > I set up (neighbour( statements on each router (Hope > > > > Radia can forgive the extra vowel !!!) and advertised > > > > the networks. > > > > > > > > I got the BGP table working but nothing was promoted > > > > to the main routing table, and therefore could4nt ping > > > > non directly connected interfaces. I tried various > > > > approaches like putting a default route in and running > > > > an IGP but still no promotion to the main table. > > > > > > > > Should this be possible with iBGP ? or is it a matter > > > > of loop avoidance i.e the AS Numbers won4t be > > > > prepended for the case of iBGP peers. > > > > > > > > Phil. > > > > > > > > __________________________________________________ > > > > Do You Yahoo!? > > > > Everything you'll ever need on one web page > > > > from News and Sport to Email and Music Charts > > > > http://uk.my.yahoo.com > > -- > > David Madland > > Sr. Network Engineer > > CCIE# 2016 > > Qwest Communications Int. Inc. > > [EMAIL PROTECTED] > > 612-664-3367 > > > > "Emotion should reflect reason not guide it" -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 "Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=40832&t=40741 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
