Subject: Demand Circuits Anomalies

From: Acee Lindem <[email-masked]>
Date: Fri, 3 May 2002 00:05:47 -0400

I've been looking (actually implementing) demand circuits in the context
of reduced flooding and OSPF PE/CE Sham Links and I seemed to have
run across a situation that doesn't seem to be handled
by RFC 1793.

   - You have two links in area 1 between routers A and B over which
     you establish adjacencies. One is configured as a demand
     circuit and one is not.

   - Router A is an ABR and is advertising a number of summary
     network advertisments. These are advertised as DoNotAge
     LSAs over the demand circuit and regular LSAs over the other
     circuit.

   - Over time (> 1800 seconds), all the DoNotAge LSAs are replaced
     with normal LSAs since they are not refreshed over the demand
     circuit but are refreshed over the non-demand circuit.

   - The non-demand circuit between A and B goes down indefinitely.

   - After MaxAge (3600 seconds), router B ages out the LSAs and
     they are unreachable even though the neighbor adjacency over
     the demand circuit is still up. Keep in mind that the summary
     network advertisements have not changed and there is no other
     path between routers A and B.

Am I missing something here or isn't this case handled?

Thanks,
--
Acee

---

From: Alex Zinin <[email-masked]>
Date: Thu, 2 May 2002 21:51:16 -0700

Acee,

  Hmmm... In the last step below, when B ages the LSAs out,
  it will flush them by flooding the MaxAge version through all
  links, including the DC one (MaxAge is considered to be a change).
  This should trigger the 'self-originated' mechanism in A to
  reoriginate the LSAs and flood the new versions back.

--
Alex

---

From: Acee Lindem <[email-masked]>
Date: Fri, 3 May 2002 01:32:42 -0400

>   reoriginate the LSAs and flood the new versions back.

Opps - that works.

Thanks,
--
Acee

---

From: Ash he <[email-masked]>
Date: Fri, 3 May 2002 11:56:38 -0700

Is it allowed theoretically to have the following
 configuration on a single router? Can you please
give its implications if yes and the reasons if not?

Intf1: 149.112.1.3/B
Intf2: 149.112.2.4/C

Any help appreciated.

Thanks,
Ash.

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