From: Scott Smith (hioctane@gmail.com)
Date: Fri Aug 31 2007 - 17:25:18 ART
While that is true that type1 metric changes along the path and the
type2 is constant this isn't the point of the show output.
What I've pointed out is there is another metric in play with
externals aside from the metric of the route. The router also
considers the cost to the ASBR when deciding if externals are truly
equal. For two externals to be considered equal everything must be
equal. Both the metric of the route as seen via "sh ip route" and the
metric to the ASBR seen via "sh ip ospf border-routers" must be equal.
-- Scott CCIE #17040 (R&S)On 8/31/07, Gary Duncanson <gary.duncanson@googlemail.com> wrote: > Thanks for that Scott. > > Looks like this demonstrates this rather well, at least how I read it. > > From OSPF Design Guide on CCO. > > sic 'External routes fall under two categories, external type 1 and external > type 2. The difference between the two is in the way the cost (metric) of > the route is being calculated. The cost of a type 2 route is always the > external cost, irrespective of the interior cost to reach that route.' > > Rgds > Gary > ----- Original Message ----- > From: "Scott Smith" <hioctane@gmail.com> > To: "Sadiq Yakasai" <sadiqtanko@gmail.com> > Cc: "Joseph Brunner" <joe@affirmedsystems.com>; "Herbert Maosa" > <asawilunda@googlemail.com>; "ISolveSystems" <support@isolvesystems.com>; > "Cisco certification" <ccielab@groupstudy.com> > Sent: Friday, August 31, 2007 7:49 PM > Subject: Re: OSPF external type-2 route load balance > > > > Bingo! > > > > A1 learns 100.100.100.0 from both 10.43.1.61 & 10.43.1.73. > > > > Before - BW 1536 to both ASBRs > > > > A1(config-router)#do sh ip route ospf > > 100.0.0.0/24 is subnetted, 1 subnets > > O E2 100.100.100.0 [110/20] via 10.43.1.61, 00:00:36, Serial1/0.1 > > [110/20] via 10.43.1.73, 00:00:36, > > Serial1/0.2 > > > > > > After - Dropped BW to 512 on s1/0.1 > > > > A1(config-subif)#do sh ip route ospf > > 100.0.0.0/24 is subnetted, 1 subnets > > O E2 100.100.100.0 [110/20] via 10.43.1.73, 00:00:06, Serial1/0.2 > > > > > > Then changed BW back to 1536 on s1/0.1 (now both are equal again) > > > > A1(config-subif)#do sh ip route ospf > > 100.0.0.0/24 is subnetted, 1 subnets > > O E2 100.100.100.0 [110/20] via 10.43.1.73, 00:00:02, Serial1/0.2 > > [110/20] via 10.43.1.61, 00:00:02, > > Serial1/0.1 > > > > The metric is a constant 20, however, for the externals OSPF also uses > > the cost to the ASBR. > > > > -- > > Scott > > CCIE #17040 (R&S) > > > > > > On 8/31/07, Sadiq Yakasai <sadiqtanko@gmail.com> wrote: > >> Can you show the Type 4 LSA database as well? > >> > >> I think the cost to the ASBR has a role to play in selecting 2 Type 5 > >> LSA's reporting the same prefix. > >> > >> I am not quite sure about this though. > >> > >> _______________________________________________________________________ > >> Subscription information may be found at: > >> http://www.groupstudy.com/list/CCIELab.html > > > > _______________________________________________________________________ > > Subscription information may be found at: > > http://www.groupstudy.com/list/CCIELab.html
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