Hi Jason, see below
-pavel skovajsa On Fri, Jan 15, 2010 at 4:57 AM, Jason LeBlanc <[email protected]> wrote: > Hello, > > We currently have Layer 3 Routed Access configured at all of our Metro Campus > locations. There are a few obvious deviations from the best practice design > guides. The current setup is: > > Core --> Datacenter Distribution --> | (fiber connect) | --> > Building Distribution --> Access > (backbone) (ABR) > (ASBR) (OSPF enabled > access switch) > > The Cisco best practice is: > > Core --> Distribution --> Access > (backbone) (ABR) (OSPF enabled access switch) > The best practices are exactly what it says - best practices - in real practice everybody finds hard to actually achieve that, due to geopolitical/other reasons. In other words the following implication is NOT true: not following best practices -> bad design -> network melts > We are running NSSA with no-summary and the range command on the Datacenter > Distribution routers. Each floor has 2 access switches (w/ OSPF running) > which each have a link back to the Building Distribution router. Vlans on > each box on each floor are mutually exclusive. > > Symptoms: > Lots of SPF re-calculations, NTP failing from Datacenter Distro -> Building > Distro, and users reporting loss of their shared drives. > > router-a#sh ip ospf stat > Area 0.0.0.0: SPF algorithm executed 7865 times > Area 192.8.208.0: SPF algorithm executed 386 times > Area 192.70.0.0: SPF algorithm executed 563 times > Area 192.100.0.0: SPF algorithm executed 93076 times Well, that last area 192.100.0.0 seems to be the culprit - what about troubleshooting it for a while, instead of redesigning whole network? Use commands like above "show ip ospf stat" and looks for Seq# and LSA Age to find the flapping LSA. Also stuff like "Debug ip ospf monitor" and "show ip ospf database database-sum" will help you. > > > Questions: > Should we be advertising (passively or non-passively) L3 Vlans into OSPF? Passively. Why would somebody do that in non-passive way and have miriads of neighbors per each vlan? > Should we be doing Totally NSSA's instead of NSSA's? Totally stubby (or totally not-so-stubby if you need ASBR) should be default design, only configure no-summary if you have specific reason. Also I don't understand the need for ASBR in your NSSA - but you probably have a reason for that. > If not is there a way to get the DR in NSSA to advertise a single > route back as default route? > Should we be sending each campus distribution router directly to the Core so > that its the 3 hops? As written above, if you have the funding to do this it will certainly make your network design nicer, but I don't see how doing this would actually massively decrement your SFP runs.... > Do you suggest tuning the OSPF dead interval to achieve subsecond convergence? Scale and speed are contradictory goals. Fast reaction to changes in network topology, tends to end up in a network that never converges and is unstable. > > > Any help advise is greatly appreciated! > > Regards, > > //LeBlanc > _______________________________________________ > 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/
