Hello Michael, Please re-read and take the time to understand. <snip>..... on to "default-information-originate *always*: > > > > this causes localy router to inject a default into OSPF > domain regardless of whether it has a default OR > not.(remember it's default can never be via OSPF) ...<snip>
Yes, it can be a bit confusing....but now You *know*. Regards, ./Randy --- On Mon, 8/27/12, Michael Ulitskiy <[email protected]> wrote: > From: Michael Ulitskiy <[email protected]> > Subject: Re: [c-nsp] bgp/ospf default route interaction > To: "Randy" <[email protected]> > Cc: "Christian Meutes" <[email protected]>, "cisco-nsp" > <[email protected]> > Date: Monday, August 27, 2012, 3:47 PM > Randy, > Thanks for the explanation. > I do understand the first part (without "always") > I guess what confused me is that I didn't expect a router > would always prefer a locally injected > ospf default over the learned one. Since both LSAs are in > the database (just checked it) I expected > it to go ahead and compare the metrics. In my example I > specifically lowered the metric of default > advertised by CORE1 and it didn't make any difference. CORE2 > still ignored it. > Anyway, it's much clearer now. > Thanks Randy and Christian, > > Michael > > > On Monday 27 August 2012 17:32:04 Randy wrote: > > Hi, > > ..actually not quite! > > > > case1: default-information-originate (core1 and core2) > > > > core2 learns 3 defaults: > > via iBGP from core1 AD 200 but loc pref 150 > > via eBGP from ISP2 AD 20 loc pref less than iBGP > learned default > > via OSPF ad 110. > > > > so on the face of it, it installs OSPF learned default > in rib....what has happended in the process is that > "default-information-originate" on Core2 *is NOT actually > working*! > > > > "default-information-originate" within OSPF *requires* > that local router have a default-route known via any other > igp/egp BUT NOT OSPF. > > > > on to "default-information-originate *always*: > > > > this causes localy router to inject a default into OSPF > domain regardless of whether it has a default OR > not.(remember it's default can never be via OSPF) > > > > so what happens in the process is core2 suppresses OSPF > learned default via core1 and now has iBGP default or eBGP > default to choose from. It as a result chooses iBGP learned > default in its rib. > > > > (hint: in your original output, you will notice both > eBGP and iBGP routes suffered from rib-failure...) > > > > HTH wrt what is happening behind the scene. > > ./Randy > > > > --- On Mon, 8/27/12, Michael Ulitskiy <[email protected]> > wrote: > > > > > From: Michael Ulitskiy <[email protected]> > > > Subject: Re: [c-nsp] bgp/ospf default route > interaction > > > To: "Christian Meutes" <[email protected]> > > > Cc: "cisco-nsp" <[email protected]> > > > Date: Monday, August 27, 2012, 1:57 PM > > > Thanks for the reply. > > > So what you're saying is that if ospf router > itself injects > > > ospf default in its ospf database then > > > it would ignore any other ospf defaults it might > receive > > > (regardless of metric) and also it wouldn't > > > install this default in the RIB. > > > Did I get it right? > > > I didn't know this rule and I'm a little > surprised, but I > > > ran a few experiments and they seem to confirm it. > > > > Thanks, > > > > > > Michael > > > > > > On Monday 27 August 2012 16:06:14 Christian Meutes > wrote: > > > > Hiho, > > > > > > > > On Aug 27, 2012, at 7:52 PM, Michael Ulitskiy > <[email protected]> > > > wrote: > > > > > > > > > Now on CORE2 I add 'always' keyword to > OSPF > > > 'default-originate' command, > > > > > making it: > > > > > > > > > > CORE2: router ospf 100 > default-information > > > originate always > > > > > > > > > > For some reason I don't understand it > changes the > > > game completely. Now > > > > > IBGP route is preferred over OSPF > > > > > > > > it's because you inject the 0/0 into OSPF on > CORE2 > > > *always*, effectively > > > > annihilating the other 0/0 advertised by > CORE1s OSPF on > > > CORE2. > > > > > > > > Thus, the only remaining defaults are the > ones learned > > > via BGP. > > > > > > > > Without the always-keyword it seems that the > OSPF route > > > is learned fast > > > > enough to prevent the BGP one to be installed > in. > > > > > > > > > > > _______________________________________________ > > > cisco-nsp mailing list [email protected] > > > https://puck.nether.net/mailman/listinfo/cisco-nsp > > > archive at http://puck.nether.net/pipermail/cisco-nsp/ > > > > > > _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
