""nrf"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > ""The Long and Winding Road"" wrote in > message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > ""Debbie Westall"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Just a thought, but how about when.... > > > > > > redistributing the routes to the other protocol using a route-map at the > > > end and tagging the routes that came from ospf. Add another route-map > > > statement that any route that has been tagged deny it. > > > > > > Example: > > > > > > router ospf 100 > > > redistribute rip metric 130 subnets route-map RIP2OSPF > > > > > > route-map RIP2OSPF permit 10 > > > set tag 66 > > > route-map RIP2OSPF permit 20 > > > > > > router rip > > > redistribute ospf 100 metric 3 route-map OSPF2RIP > > > route-map OSPF2RIP deny 10 > > > match tag 66 > > > route-map OSPF2RIP permit 20 > > > > > > I just went through the ACP class and this was their solution to a > > > similiar situation. > > > > > > oh, sure, and this is one way of doing things. > > > > the CCIE prep materials generally try to force you to master several > > alternatives. Cisco ASET, where I got this particular exercise, > > unfortunately has but a single answer, and their answer, as determined by > > their grading scripts, is distribute-lists. This gets back to my posted > > concern about the future of CCIE Lab testing, where everything is done by > > script, and where there is only one answer, whether or not there are > > alternatives. > > > > route tagging is indeed an excellent way to control things, and should be > > part of any CCIE Lab participant's toolbox. > > > > > The problem with this method is, of course, what if the best path to reach a > route really is to go through the other IGP domain? For example, what if > there is a split in your OSPF network, and for one particular OSPF router to > reach another OSPF router, the best (heck, the only) path is to go through a > RIP domain? All this filtering based on access-list or route-tag or > whatever merely serves to break the redundancy that was a big reason for > your using a routing protocol in the first place. > >
agreed. however, since the CCIE Lab has about as much to do with good design as dog food has to do with good cooking, all that matters is reachability. in the particular practice lab, the redistribution is insidious, RIP routes on R3 are redistributed into an IS-IS domain, and the IS-IS routes are redistributed into OSPF on R6. OSPF router R2 then propogates those routes back to R3. Since the OSPF admin distance is 110, a route that originated in the RIP domain is received on R3 as an OSPF route, and is installed into R3's routingtable because of lower AD. A cascade effect occurs, with the RIP routes having been overwritten. Since there are no RIP routes to resdistribute into IS-IS, the routes age out of the IS-IS domain. Therefore they cannot be advertised into OSPF. Therefore they age out of OSPF. Therefore R3 no longer has these routes as OSPF routes, so the RIP routes are reintroduced into the routing table ( AD 120 ) and the cycle starts again. granted, neither you nor I nor anyone in their right mind would ever design a network this way. but here, the purpose of the exercise is to cause folks to understand how things work, and options for fixing broken things. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63227&t=63144 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
