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Is OSPF acting up or am I forgetting my theory?

Unanswered Question
Sep 19th, 2013
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Hey all,


I'm having a weird OSPF issue with a particular network I'm working on.


Pretty simple setup, 4 locations, 4 x 2911 routers connected via Metro E and all advertise a default route. All 4 sites have another router behind the 2911s. Main site is at 10.89.228.1 so I want it to be the default route. However, for all locations all the internal routers do not pick up 10.89.229.40 as the default. Instead the pick the router that's internal


4 routers:


SITE A-  10.89.228.40 **MAIN**

SITE B- 10.89.229.40  (here's where all the output below is from)

SITE C- 10.88.7.40

SITE D- 10.88.6.40


internal routers are at .40 at all locations


Now two questions... A. I thought that E2 routes are always prefered over E1 routes.. this is not what I'm seeing here: see exhibit A

B. I thought that the default route with the lowest metric would be in the routing table - this is not what I'm seeing here either see exhibit B.




The output below comes from the internal router behind SITE B. So it has an ip address that's in the same LAN... 10.89.229.0/24


EXHIBIT A -- All default routes are advertized as type 1  -- Main site is advertizing an type 2 default route:



#sh ip os da ex 0.0.0.0 | i Metric|Adv|Typ

                Type-5 AS External Link States

  LS Type: AS External Link

  Advertising Router: 10.88.6.40

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 10

  LS Type: AS External Link

  Advertising Router: 10.88.7.40

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 8

  LS Type: AS External Link

  Advertising Router: 10.89.228.40

        Metric Type: 2 (Larger than any link state path)

        Metric: 5

  LS Type: AS External Link   **THIS GETS IN THE ROUTING TABLE EVEN THOUGH METRIC TYPE ABOVE IS 2*

  Advertising Router: 10.89.229.40

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 10



EXHIBIT B --- All default routes are type 1 -- MAIN SITE HAS THE LOWEST METRIC


#sh ip os da ex 0.0.0.0 | i Ty|Ad|c:

                Type-5 AS External Link States

  LS Type: AS External Link

  Advertising Router: 10.88.6.40

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 10

        Forward Address: 0.0.0.0

  LS Type: AS External Link

  Advertising Router: 10.88.7.40

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 8

        Forward Address: 0.0.0.0

  LS Type: AS External Link

  Advertising Router: 10.89.228.40

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 5

        Forward Address: 0.0.0.0

  LS Type: AS External Link

  Advertising Router: 10.89.229.40 **THIS GETS IN THE ROUTING TABLE EVEN THOUGH 10>5**

        Metric Type: 1 (Comparable directly to link state metric)

        Metric: 10 

        Forward Address: 0.0.0.0



What am I missing? I thought I knew OSPF pretty well.. I guess I was mistaken.

thank you!



PS: I did clear ospf processes every time I was making changes..

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Harold Ritter Thu, 09/19/2013 - 19:34
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  • Cisco Employee,

Hi Anestis,


It would help if you could provide the unfiltered output for "sh ip os da ex 0.0.0.0".


Regards

Rolf Fischer Fri, 09/20/2013 - 08:21
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  • Blue, 1500 points or more

Hi,


It would help if you could provide the unfiltered output for "sh ip os da ex 0.0.0.0".


... and the output of  show ip ospf border-routers as well please.


Regards

Rolf

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