From: Eric Poulin (epoulins@yahoo.com)
Date: Tue May 22 2007 - 13:00:45 ART
I understand that intra-area routes are preferred over inter-area routes, and inter-area
routes are preferred over external-routes, but the route coming from R4 on both links is
an inter-area route. Unless OSPF prefers "advertising router" within Area0 over Area45, I
don't see why R5 prefers the Frame Relay link with a higher cost.
--- "Huizinga, Rene" <rhuizinga@upcbroadband.com> wrote:
> I believe this comes down to the intra-area over inter-area rule in OSPF.
> If I understand the description correctly from this email, the remote
> router-id may play a role in here. Since that's in Area0, it may be the
> tie-breaker in this. If this is this tie-breaker, then intra- over
> inter-area, regardless of cost et all !
>
> Cya
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Eric
> Poulin
> Sent: Tuesday, May 22, 2007 4:42 PM
> To: M S; ccielab@groupstudy.com
> Subject: RE: Question about OSPF preferring higher cost route from area0
> over lower cost from another area?
>
> Here's the output:
>
> Rack1R5#sh run | beg router ospf
> router ospf 1
> router-id 150.1.5.5
> log-adjacency-changes
> network 150.1.5.5 0.0.0.0 area 0
> network 183.1.0.5 0.0.0.0 area 0
> network 183.1.45.5 0.0.0.0 area 45
>
>
> --- M S <michaelgstout@hotmail.com> wrote:
>
>
> ---------------------------------
>
> I would like to see the "show run | b router ospf" output.
>
> Thank you.
>
>
>
>
> ---------------------------------
>
> From: Eric Poulin <epoulins@yahoo.com>
> Reply-To: Eric Poulin <epoulins@yahoo.com>
> To: ccielab@groupstudy.com
> Subject: Question about OSPF preferring higher cost route from area0 over
> lower cost from another area?
> Date: Mon, 21 May 2007 21:04:27 -0700 (PDT) Hi GS,
>
> I have two routers, R4 and R5, running OSPF between each other over Frame
> Relay (Area0) and also Ethernet (Area45). R5 is learning an inter-area route
> 150.1.6.6/32 from R4 over both links. The OSPF cost to reach R4 over the FR
> is 64 and Ethernet is 1. Please can someone explain me why R5 prefers the
> route over the frame Relay as opposed to the Ethernet? I was expecting R5 to
> chose its Ethernet link with a cumulative cost of 3 instead of the FR
> interface with a cumulative cost of 66? Are routes for the same prefix
> preferred within Area0?
>
> Thanks for your help,
> Eric
>
> ----------------------------
> Rack1R5#sh ip ospf neighbor
> Neighbor ID Pri State Dead Time Address Interface
> 150.1.4.4 0 FULL/DROTHER 868 msec 183.1.0.4 Serial0/0
> 150.1.4.4 1 FULL/DR 00:01:46 183.1.45.4
> FastEthernet0/1
> ----------------------------
> Rack1R5#sh ip route ospf
> 150.1.0.0/16 is variably subnetted, 9 subnets, 2 masks
> O IA 150.1.6.6/32 [110/66] via 183.1.0.4, 00:05:09, Serial0/0
> ----------------------------
> Rack1R5#sh ip ospf database summ 150.1.6.6
>
> OSPF Router with ID (150.1.5.5) (Process ID 1)
>
> Summary Net Link States (Area 0)
>
> Routing Bit Set on this LSA
> LS age: 1865
> Options: (No TOS-capability, DC, Upward)
> LS Type: Summary Links(Network)
> Link State ID: 150.1.6.6 (summary Network Number)
> Advertising Router: 150.1.4.4
> LS Seq Number: 80000012
> Checksum: 0xC323
> Length: 28
> Network Mask: /32
> TOS: 0 Metric: 2
>
>
> Summary Net Link States (Area 45)
>
> LS age: 1865
> Options: (No TOS-capability, DC, Upward)
> LS Type: Summary Links(Network)
> Link State ID: 150.1.6.6 (summary Network Number)
> Advertising Router: 150.1.4.4
> LS Seq Number: 80000012
> Checksum: 0xC323
> Length: 28
> Network Mask: /32
> TOS: 0 Metric: 2
> ----------------------------
> Rack1R5#sh ip ospf database router 150.1.4.4
>
> OSPF Router with ID (150.1.5.5) (Process ID 1)
>
> Router Link States (Area 0)
>
> Routing Bit Set on this LSA
> LS age: 186
> Options: (No TOS-capability, DC)
> LS Type: Router Links
> Link State ID: 150.1.4.4
> Advertising Router: 150.1.4.4
> LS Seq Number: 80000018
> Checksum: 0x8AE6
> Length: 48
> Area Border Router
> Number of Links: 2
>
> Link connected to: a Transit Network
> (Link ID) Designated Router address: 183.1.0.5
> (Link Data) Router Interface address: 183.1.0.4
> Number of TOS metrics: 0
> TOS 0 Metrics: 64
>
> Link connected to: a Stub Network
> (Link ID) Network/subnet number: 150.1.4.4
> (Link Data) Network Mask: 255.255.255.255
> Number of TOS metrics: 0
> TOS 0 Metrics: 1
>
>
>
> Router Link States (Area 45)
>
> Routing Bit Set on this LSA
> LS age: 576
> Options: (No TOS-capability, DC)
> LS Type: Router Links
> Link State ID: 150.1.4.4
> Advertising Router: 150.1.4.4
> LS Seq Number: 8000001C
> Checksum: 0x6C97
> Length: 36
> Area Border Router
> Number of Links: 1
>
> Link connected to: a Transit Network
> (Link ID) Designated Router address: 183.1.45.4
> (Link Data) Router Interface address: 183.1.45.4
> Number of TOS metrics: 0
> TOS 0 Metrics: 1
> ----------------------------
>
>
>
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