Re: OSPF Tricks of the Trade [7:66308]
See feedback inline. Eric - Original Message - From: "The Long and Winding Road" To: Sent: Thursday, March 27, 2003 7:09 AM Subject: OSPF Tricks of the Trade [7:66308] > After wrestling with Solie this afternoon, it suddenly occurred to me that > there is a typical instruction in the various practice labs that can end up > driving you nuts if you look at it from one direction, but which is really > simple if looked at from another. > > The topology: several routers over frame relay. Usually four routers. One > acts as hub, The others as spokes. > > the instruction: you must use subinterfaces only on the hub. On the spokes > you MUST use the physical interfaces. two of the spoke routes connect to the > hub via one subinterface. The other router connects to the hub on the other > subinterface. > > the catch: some bizarre restriction or other about network types, commands > that can or cannot be used, the usual BS. > > It occurs to me that working backwards, you can solve most problems, > whatever the restrictions and twists. > > Frame relay: OSPF default > - > > physical interface non broadcast > > subinterface - p2ppoint-to-point > > subinterface - multipoint non broadcast > > I think the knee jerk reaction is to create a multipoint subinterface for > the link to the two spoke routers, and a p2p subinterface for the link to > the single spoke router. Then moan in despair as you realize that the > instructions forbid the use of any ip ospf network commands anywhere. > > But if you look from the higher level viewpoint, you see that the physical > and the multipoint subinterface default to the same type of OSPF network. > Life is easier after that. Yes, that's the first thing I do: determine the default OSPF network type of involved interfaces After that investigate what this means for: - hello and dead timers (are they equal yes/no?); - DR/BDR election (yes/no); if yes: manual configuration required (by means of priority in neighbor statement), or is it automatic? - manual neighbor configuration required (yes/no)? > > Is this making sense? I'm at the end of a very long day, with too many > subtleties floating around in what's left of my brain. > > Good night, everyone. > > > > > > > > -- > TANSTAAFL > "there ain't no such thing as a free lunch" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71302&t=66308 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: OSPF Tricks of the Trade [7:66308]
Another good one!! Could also add that Ospf timers need to be kept in mind if the hub is using say for ex. a multipoint and the spoke a point-to-point and the task is NOT to configure any #ip ospf network cmd. on the spokes >From: "The Long and Winding Road" >Reply-To: "The Long and Winding Road" >To: [EMAIL PROTECTED] >Subject: OSPF Tricks of the Trade [7:66308] >Date: Thu, 27 Mar 2003 05:09:30 GMT > >After wrestling with Solie this afternoon, it suddenly occurred to me that >there is a typical instruction in the various practice labs that can end up >driving you nuts if you look at it from one direction, but which is really >simple if looked at from another. > >The topology: several routers over frame relay. Usually four routers. One >acts as hub, The others as spokes. > >the instruction: you must use subinterfaces only on the hub. On the spokes >you MUST use the physical interfaces. two of the spoke routes connect to >the >hub via one subinterface. The other router connects to the hub on the other >subinterface. > >the catch: some bizarre restriction or other about network types, commands >that can or cannot be used, the usual BS. > >It occurs to me that working backwards, you can solve most problems, >whatever the restrictions and twists. > >Frame relay: OSPF default >- > >physical interface non broadcast > >subinterface - p2ppoint-to-point > >subinterface - multipoint non broadcast > >I think the knee jerk reaction is to create a multipoint subinterface for >the link to the two spoke routers, and a p2p subinterface for the link to >the single spoke router. Then moan in despair as you realize that the >instructions forbid the use of any ip ospf network commands anywhere. > >But if you look from the higher level viewpoint, you see that the physical >and the multipoint subinterface default to the same type of OSPF network. >Life is easier after that. > >Is this making sense? I'm at the end of a very long day, with too many >subtleties floating around in what's left of my brain. > >Good night, everyone. > > > > > > > >-- >TANSTAAFL >"there ain't no such thing as a free lunch" _ MSN 8 with e-mail virus protection service: 2 months FREE* http://join.msn.com/?page=features/virus Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=66321&t=66308 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
OSPF Tricks of the Trade [7:66308]
After wrestling with Solie this afternoon, it suddenly occurred to me that there is a typical instruction in the various practice labs that can end up driving you nuts if you look at it from one direction, but which is really simple if looked at from another. The topology: several routers over frame relay. Usually four routers. One acts as hub, The others as spokes. the instruction: you must use subinterfaces only on the hub. On the spokes you MUST use the physical interfaces. two of the spoke routes connect to the hub via one subinterface. The other router connects to the hub on the other subinterface. the catch: some bizarre restriction or other about network types, commands that can or cannot be used, the usual BS. It occurs to me that working backwards, you can solve most problems, whatever the restrictions and twists. Frame relay: OSPF default - physical interface non broadcast subinterface - p2ppoint-to-point subinterface - multipoint non broadcast I think the knee jerk reaction is to create a multipoint subinterface for the link to the two spoke routers, and a p2p subinterface for the link to the single spoke router. Then moan in despair as you realize that the instructions forbid the use of any ip ospf network commands anywhere. But if you look from the higher level viewpoint, you see that the physical and the multipoint subinterface default to the same type of OSPF network. Life is easier after that. Is this making sense? I'm at the end of a very long day, with too many subtleties floating around in what's left of my brain. Good night, everyone. -- TANSTAAFL "there ain't no such thing as a free lunch" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=66308&t=66308 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
