Re: OSPF NSSA problems

From: Bogdan Sass (bogdan.sass@catc.ro)
Date: Mon Sep 22 2008 - 07:14:18 ART


Hong Chan wrote:
> Dear Bogdan,
>
> Thanks your remind and I agree it's strange also.
> Can you show the result of
> show ip ospf database externa 158.1.0.0 <http://158.1.0.0>
> on SW4? I wanna to know which router redistribute this route to SW4

    Of course - the subnet is redistributed by R3 (the router at the
other end of the two areas), using a "redistribute connected" statement
(in the original lab, the subnet was redistributed from EIGRP, with the
same result).

/Rack1SW4#sh ip ospf data ex 158.1.0.0

            OSPF Router with ID (150.1.10.10) (Process ID 1)

                Type-5 AS External Link States

  Routing Bit Set on this LSA
  LS age: 131
  Options: (No TOS-capability, DC)
  LS Type: AS External Link
  Link State ID: 158.1.0.0 (External Network Number )
  Advertising Router: 150.1.3.3
  LS Seq Number: 80000001
  Checksum: 0x5310
  Length: 36
  Network Mask: /24
        Metric Type: 2 (Larger than any link state path)
        TOS: 0
        Metric: 20
        Forward Address: 0.0.0.0
        External Route Tag: 0/
   
    The route is advertised by 150.1.3.3 (R3), with a forwarding address
of 0.0.0.0 .

    SW4 has only one routing table entry for 150.1.3.3 (as expected, it
only uses the intra-area route):
/
Rack1SW4#sh ip ro 150.1.3.3
Routing entry for 150.1.3.3/32
  Known via "ospf 1", distance 110, metric 66, type intra area
  Last update from 158.1.1.1 on Vlan110, 00:03:07 ago
  Routing Descriptor Blocks:
  * 158.1.1.1, from 150.1.3.3, 00:03:07 ago, via Vlan110
      Route metric is 66, traffic share count is 1/

    However, it still installs two routes for the external address:

/Rack1SW4#sh ip ro 158.1.0.0 255.255.255.0
Routing entry for 158.1.0.0/24
  Known via "ospf 1", distance 110, metric 20, type extern 2, forward
metric 65
  Last update from 158.1.1.1 on Vlan110, 00:05:03 ago
  Routing Descriptor Blocks:
  * 158.1.34.1, from 150.1.3.3, 00:05:03 ago, via FastEthernet1/13
      Route metric is 20, traffic share count is 1
    158.1.1.1, from 150.1.3.3, 00:05:03 ago, via Vlan110
      Route metric is 20, traffic share count is 1

   
/ If you need any additional details/output, please let me know (I
would also draw a diagram, but I really don't know how I could put this
topology in ASCII format :) ).

    Thank you for your help,

-- 
Bogdan Sass
CCAI,CCNP,CCSP,JNCIA-ER
Information Systems Security Professional
"Curiosity was framed - ignorance killed the cat"

Blogs and organic groups at http://www.ccie.net



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