Re: OSPF Multilink routing issue

Not sure I fully understand your topology ... but on R2, OSPF thinks this is
an inter-area route that has been also been configured in EIGRP. Which
router is performing the redistribution for network 5.5.5.5?

I would start by looking at which router is originating this route into OSPF
and follow this through the network to see where it takes a suboptimal
path.

Also, the metric is changing, so it must be a E1. To be honest, the outputs
you are including do not tell me much other than OSPF believes the route to
R6 is the best route to take ...

BTW ... why do you have a virtual link configured between 2 and 5? Just
curious ... area 0 off of R2, and another area 0.0.37.128 is configured on
each router. Given what I see here, I do not know see why virtual links
would be configured.

A quick test is to shut down R6. Does the link to R5 become the preferred
path to the route - 5.5.5.5? If so, why did it now become the preferred
path? If after this test, OSPF still does not prefer the path directly to
R5, then it must think the updates from R5 are invalid and is rejecting
these or it is not getting any updates from R5 about network 5.5.5.5 ...

Sorry I cannot be more help ... perhaps another on this list has tried this
lab and knows what you are facing.

HTH,

Andrew Lee Lissitz

On Tue, Sep 22, 2009 at 8:49 PM, Rob Phillips <rrphillips_at_swankav.com>wrote:

> I have an issue that has been racking my brain and I just can not figure it
> out.
>
> I have 3 routers Using Multilink PPP. R6 ----- R2 ------ R5
>
> When all links are up R2 believes any routes behind R5 are actually
> reachable
> through R6. The example below is a loopback on R5 (5.5.5.5). In all cases
> it
> knows that 143.43.65.5 is the next hop, however the router believes to get
> to
> 143.43.65.5 is through Multilink 2 when it has to route. (aka pinging
> 143.43.65.5 works from R2, but every route in the routing table shows
> 143.43.65.5 via Multilink 2 when it should actually follow Multilink 1)
>
> Area 0 is on a loopback on R2.
>
>
>
> Any help would be great. I am pulling out the few hairs I have left on the
> top of my head. I have tried every show command I and think of and even
> started trying show commands I never heard off. Tried several different
> debugs but nothing!
>
>
>
> If I don't figure it out soon, my head may get so bare and shiney that
> light
> bouncing off of it may blind a proctor during my lab. How many points do
> you
> lose for that?
>
>
>
> R2
>
> interface Multilink1
> ip address 143.43.65.2 255.255.255.0
> ip ospf network point-to-multipoint
> ip ospf hello-interval 10
> ppp multilink
> ppp multilink group 1
> !
> interface Multilink2
> ip address 143.43.65.2 255.255.255.0
> ip ospf network point-to-multipoint
> ip ospf hello-interval 10
> ppp multilink
> ppp multilink group 2
>
> interface Serial0/1/0
> no ip address
> encapsulation frame-relay
> frame-relay traffic-shaping
> frame-relay interface-dlci 205 ppp Virtual-Template1
> frame-relay interface-dlci 206 ppp Virtual-Template2
> frame-relay interface-dlci 215 ppp Virtual-Template1
> frame-relay interface-dlci 216 ppp Virtual-Template2
> frame-relay interface-dlci 225 ppp Virtual-Template1
> frame-relay interface-dlci 226 ppp Virtual-Template2
> no frame-relay inverse-arp
> !
> interface Virtual-Template1
> no ip address
> ppp multilink
> ppp multilink group 1
> !
> interface Virtual-Template2
> no ip address
> ppp multilink
> ppp multilink group 2
>
> router ospf 1
> router-id 2.2.2.2
> log-adjacency-changes
> area 0.0.37.128 virtual-link 5.5.5.5
> redistribute eigrp 24 subnets
> network 143.43.65.2 0.0.0.0 area 0.0.37.128
>
> Routing entry for 5.5.5.5/32
> Known via "ospf 1", distance 110, metric 1191, type inter area
> Redistributing via eigrp 24
> Advertised by eigrp 24 metric 1 1 1 1 1
> Last update from 143.43.65.5 on Multilink2, 00:35:54 ago
> Routing Descriptor Blocks:
> * 143.43.65.5, from 5.5.5.5, 00:35:54 ago, via Multilink2
> Route metric is 1191, traffic share count is 1
>
> Neighbor ID Pri State Dead Time Address Interface
> 5.5.5.5 0 FULL/ - - 143.43.65.5 OSPF_VL0
> 6.6.6.6 0 FULL/ - 00:01:32 143.43.65.6
> Multilink2
> 5.5.5.5 0 FULL/ - 00:01:48 143.43.65.5
> Multilink1
>
>
>
> R5
>
>
> interface Multilink1
> ip address 143.43.65.5 255.255.255.0
> ip ospf network point-to-point
> ppp multilink
> ppp multilink group 1
>
> interface Serial0/1/0
> no ip address
> encapsulation frame-relay
> frame-relay traffic-shaping
> frame-relay interface-dlci 502 ppp Virtual-Template1
> frame-relay interface-dlci 512 ppp Virtual-Template1
> frame-relay interface-dlci 522 ppp Virtual-Template1
> no frame-relay inverse-arp
> interface Virtual-Template1
> no ip address
> ppp multilink
> ppp multilink group 1
> !
> router ospf 1
> router-id 5.5.5.5
> log-adjacency-changes
> area 0.0.37.128 virtual-link 2.2.2.2
> network 143.43.65.5 0.0.0.0 area 0.0.37.128
> !
>
> Neighbor ID Pri State Dead Time Address Interface
> 2.2.2.2 0 FULL/ - - 143.43.65.2 OSPF_VL0
> 192.168.2.8 1 FULL/DR 00:00:38 143.43.200.2
> FastEthernet0/0
> 2.2.2.2 0 FULL/ - 00:01:30 143.43.65.2
> Multilink1
>
>
> R6
>
> interface Multilink2
> ip address 143.43.65.6 255.255.255.0
> ip ospf network point-to-point
> ppp multilink
> ppp multilink group 2.
>
> interface Serial0/1/0
> no ip address
> encapsulation frame-relay
> frame-relay traffic-shaping
> frame-relay interface-dlci 602 ppp Virtual-Template1
> frame-relay interface-dlci 612 ppp Virtual-Template1
> frame-relay interface-dlci 622 ppp Virtual-Template1
> no frame-relay inverse-arp
>
> interface Virtual-Template1
> no ip address
> ppp multilink
> ppp multilink group 2
> !
> router ospf 1
> router-id 6.6.6.6
> log-adjacency-changes
> network 143.43.65.6 0.0.0.0 area 0.0.37.128
>
> Neighbor ID Pri State Dead Time Address Interface
> 2.2.2.2 0 FULL/ - 00:01:56 143.43.65.2
> Multilink2
> 143.43.96.9 0 FULL/ - 00:00:39 143.43.96.9 MFR1.1
>
> Known via "ospf 1", distance 110, metric 2381, type inter area
> Last update from 143.43.65.2 on Multilink2, 00:44:10 ago
> Routing Descriptor Blocks:
> * 143.43.65.2, from 5.5.5.5, 00:44:10 ago, via Multilink2
> Route metric is 2381, traffic share count is 1
>
>
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-- 
Andrew Lee Lissitz
all.from.nj_at_gmail.com
Blogs and organic groups at http://www.ccie.net