Re: OSPF filtering with administrative distance

I had the same problem.. looks like changing the AD for 150.1.6.6 changes
the metric of both routes.
The only solution I got was putting 150.1.6.6 with distance 255...
After that it was possible to decrease AD of 150.1.3.3....as below.

I think it is a bug. Please correct me if I am wrong.

Thanks in advance.

router ospf 1
 router-id 150.1.5.5
 log-adjacency-changes
 no discard-route internal
 area 0 range 150.1.0.0 255.255.252.0
 distribute-list prefix DENYR1R2 in
 distance 250 150.1.6.6 0.0.0.0 67
!
no ip http server
ip forward-protocol nd
!
!
!
!
access-list 67 permit 155.1.67.0

Rack1R5(config-router)#do sh ip route | beg 155.1.67.0
O IA 155.1.67.0/24 [250/75] via 155.1.0.3, 00:00:31, Serial1/0
------------ both changing
                               [250/75] via 155.1.0.1, 00:00:31, Serial1/0

###############################################################

router ospf 1
 router-id 150.1.5.5
 log-adjacency-changes
 no discard-route internal
 area 0 range 150.1.0.0 255.255.252.0
 distribute-list prefix DENYR1R2 in
 distance 255 150.1.6.6 0.0.0.0 67 ------------- taking out
 distance 80 150.1.3.3 0.0.0.0 67
!
no ip http server
ip forward-protocol nd
!

access-list 67 permit 155.1.67.0
!

Rack1R5(config-router)#do sh ip route | beg 155.1.67.0
O IA 155.1.67.0/24 [80/75] via 155.1.0.3, 00:00:44, Serial1/0
------------- now works

giuks

-----------------------------------------------------
Giuliano C. G. Barros
giuliano.barros_at_gmail.com
Cisco Certified Network Professional
-----------------------------------------------------

On Sun, Aug 23, 2009 at 5:04 AM, <mihai.grigore_at_orange-ftgroup.com> wrote:

> Fellow experts,
>
> I have a question on OSPF filtering with administrative distance.
> I have a route to segment 155.1.67.0/24 injected in OSPF by 2 routers, R3
> and
> R6 as foll:
>
> Rack1R5(config-router)#do sh ip o da sum 155.1.67.0
>
> 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: 318
> Options: (No TOS-capability, DC, Upward)
> LS Type: Summary Links(Network)
> Link State ID: 155.1.67.0 (summary Network Number)
> Advertising Router: 150.1.3.3 <<< R3
> LS Seq Number: 8000005B
> Checksum: 0x97CB
> Length: 28
> Network Mask: /24
> TOS: 0 Metric: 2
>
> Routing Bit Set on this LSA
> LS age: 14 (DoNotAge)
> Options: (No TOS-capability, DC, Upward)
> LS Type: Summary Links(Network)
> Link State ID: 155.1.67.0 (summary Network Number)
> Advertising Router: 150.1.6.6 <<< R6
> LS Seq Number: 80000001
> Checksum: 0x1B9D
> Length: 28
> Network Mask: /24
> TOS: 0 Metric: 1
>
>
> The task says to send traffic from R5 to 155.1.67.0/24 towards R3, using
> AD.
>
> I see 2 options here: either lowering the AD for this segment from R3 or
> increasing the AD from R6.
>
>
> I tried lowering the AD for 155.1.67.0/24 advertised by R3 but it did not
> work!!! no matter what I did.
>
> router ospf 1
> router-id 150.1.5.5
> log-adjacency-changes
> no discard-route internal
> area 0 range 150.1.0.0 255.255.252.0
> distribute-list prefix L0_R1_R2 in
> distance 50 150.1.3.3 0.0.0.0 10
>
>
> A debug ip routing revealed that the AD for 155.1.67.0/24 received from R3
> (150.1.3.3) was changed:
>
> *Aug 19 09:00:58.929: RT: add 155.1.67.0/24 via 155.1.0.3, ospf metric
> [50/66]
> <<<<<<<<<
> *Aug 19 09:00:58.933: RT: NET-RED 155.1.67.0/24
> *Aug 19 09:00:58.933: RT: add 155.1.67.0/24 via 155.1.0.1, ospf metric
> [110/66]
> *Aug 19 09:00:58.933: RT: NET-RED 155.1.67.0/24
> *Aug 19 09:00:58.933: RT: SET_LAST_RDB for 155.1.79.0/24
> NEW rdb: via 155.1.0.3
>
>
> But the routing table did not show this up. Here you are the result:
>
> Routing entry for 155.1.67.0/24
> Known via "ospf 1", distance 110, metric 66, type inter area
> Last update from 155.1.0.1 on Serial0/0, 00:02:15 ago
> Routing Descriptor Blocks:
> * 155.1.0.3, from 150.1.3.3, 00:02:15 ago, via Serial0/0
> Route metric is 66, traffic share count is 1
> 155.1.0.1, from 150.1.6.6, 00:02:15 ago, via Serial0/0
> Route metric is 66, traffic share count is 1
>
>
> The only thing that worked was to set the AD to 255 for the segment
> 155.1.67.0/24 received from R6!!!
>
> Rack1R5(config)#router ospf 1
> Rack1R5(config-router)#no distance 50 150.1.3.3 0.0.0.0 10
> Rack1R5(config-router)#distance 255 150.1.6.6 0.0.0.0 10
>
> Rack1R5(config-router)#do sh ip rou 155.1.67.0
> Routing entry for 155.1.67.0/24
> Known via "ospf 1", distance 110, metric 66, type inter area
> Last update from 155.1.0.3 on Serial0/0, 00:00:06 ago
> Routing Descriptor Blocks:
> * 155.1.0.3, from 150.1.3.3, 00:00:06 ago, via Serial0/0
> Route metric is 66, traffic share count is 1
>
> Is this kind of a bug? Why this behavior??
> I am on a 2611XM running IOS c2600-adventerprisek9-mz.124-17.bin
>
>
> Thank you for your time to read this.
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Thu Sep 03 2009 - 12:02:27 ART