Thanks for the info. It has given me a few more ideas at things to look at.
Here are the answers to your questions so hopefully I can explain my setup
better.
Area 0 like I said is on loopback 1 on R2. R2, R5 and R6's Multilink Frame
relay is within area 0.0.37.128. Now the 5.5.5.5 address is on a loopback on
R5 and that loop back is in area 51. As such I need the virtual link to brink
both the Area 51 and also another area 50 is also on R5 into OSPF.
R2 is doing redistribution between both OSPF and EIGRP and just happens to be
the most central router of all of them within my layout.
The hard part is that 5.5.5.5 is just 1 hope away from R2. I event tested by
putting the 5.5.5.5 into area 0.0.37.128 as well but have the exact same
result.
The quick test I have done several times. If I shut down R6's serial
interface that links R6 to R2 then R2 starts routing correctly. As soon as I
re-enable it it switches back to wanting to use Multilink 2.
I have tried to figure out why it thinks it is the best path by every means I
can. I was ip routing debugs, ip os packet debugs, Ip os rib debug. Here is
the debug ip os SPF which shows it wanting to pick Multilink 2 as a better
path.
*Sep 22 19:40:44.195: %LINK-3-UPDOWN: Interface Multilink2, changed state to
down
*Sep 22 19:40:44.207: %LINK-3-UPDOWN: Interface Multilink2, changed state to
up
R2(config-if)#
*Sep 22 19:40:44.699: OSPF: Schedule SPF in area 0.0.37.128
Change in LS ID 2.2.2.2, LSA type R, spf-type Full
*Sep 22 19:40:44.699: OSPF: Schedule SPF in area 0
Change in LS ID 2.2.2.2, LSA type R, spf-type Full
R2(config-if)#
*Sep 22 19:40:45.191: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Virtual-Access6, changed state to down
*Sep 22 19:40:45.207: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Multilink2, changed state to up
R2(config-if)#
*Sep 22 19:40:47.203: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Virtual-Access6, changed state to up
R2(config-if)#
*Sep 22 19:40:49.027: OSPF: Detect change in LSA type 1, LSID 6.6.6.6, from
6.6.6.6 area 0.0.37.128
*Sep 22 19:40:49.027: OSPF: Schedule SPF in area 0.0.37.128
Change in LS ID 6.6.6.6, LSA type R, spf-type Full
*Sep 22 19:40:49.027: %OSPF-5-ADJCHG: Process 1, Nbr 6.6.6.6 on Multilink2
from LOADING to FULL, Loading Done
*Sep 22 19:40:49.699: OSPF: running SPF for area 0.0.37.128, SPF-type Full
*Sep 22 19:40:49.699: OSPF: Initializing to run spf
*Sep 22 19:40:49.699: OSPF - spf_intra() - rebuilding the tree
*Sep 22 19:40:49.699: It is a router LSA 2.2.2.2. Link Count 3. V-bit set
*Sep 22 19:40:49.699: Processing link 0, id 143.43.65.2, link data
255.255.255.255, type 3, cost 0
*Sep 22 19:40:49.699: OSPF: Add better path to LSA ID 143.43.65.2, gateway
143.43.65.2, dist 0
*Sep 22 19:40:49.699: OSPF: Add path: next-hop 143.43.65.2, interface
Multilink2
*Sep 22 19:40:49.699: Processing link 1, id 5.5.5.5, link data 143.43.65.2,
type 1, cost 1190
*Sep 22 19:40:4
R2(config-if)#9.699: OSPF: Add better path to LSA ID 5.5.5.5, gateway
143.43.65.5, dist 1190
*Sep 22 19:40:49.699: OSPF: putting LSA on the clist LSID 5.5.5.5, Type 1, Adv
Rtr. 5.5.5.5
*Sep 22 19:40:49.699: OSPF: Add path: next-hop 143.43.65.5, interface
Multilink2
________________________________
From: ALL From_NJ [mailto:all.from.nj_at_gmail.com]
Sent: Tue 9/22/2009 9:11 PM
To: Rob Phillips
Cc: ccielab_at_groupstudy.com
Subject: 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.netReceived on Tue Sep 22 2009 - 21:48:45 ART
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