Comments inline At 11:19 AM 4/9/2002 -0400, Chuck wrote: >Ah, but there is this little thing called "the standard", and the standard >requires that it be done the way it is because BGP SHOULD be advertising >only REACHABLE nets. What would the internet be, if unreachable nets were >advertised willy nilly? ;->
Sure.. BGP synchronization (particularly with OSPF) hasn't been on the BGP standards track for a while. >I think it was Avi Freeman ( sp? ) who put it so poetically: ( and I am >paraphrasing ) A BGP route is a promise. Putting BGP into the your IGP would be a threat >I haven't researched, but I would wager a guess that the "no synch" option >was added in a later revision of the BGP standard based on real world >experience. It is a concession to human frailty in a protocol that requires >perfection. It is also the start of the proverbial primrose path that can >lead you to hell in a handbasket real fast, if you don't understand the >differences between BGP operation and the behaviour of the other routing >protocols. I think synch, beyond OSPF-BGP interaction, is a vendor implementation issue, and not actually described in BGPv4 (or v3 for that matter if i recall correctly) >See what happens when you read too much Raymond Chandler? :-> > >Chuck > > > >""Peter van Oene"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > I don't disagree with most of your points, but really think synch should >be > > disabled in all cases at all times along with auto summary. It should be > > disabled by default and indeed shouldn't even be included as a >configurable > > option. > > > > At 11:28 AM 4/8/2002 -0400, you 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" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=40945&t=40741 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
