[quagga-dev 4336] problem with ospf default-information originate

J.J. Krabbendam jkrabbendam at aimsys.nl
Fri Aug 25 11:37:23 BST 2006


Hi,

There is a problem (seen in at least 0.98.5, 0.99.3 and 0.99.4) with the 
advertisements of ospf default routes (default-information originate) if the
following scenario is followed:
o router ospf
o    network ....
o    default-information originate   #This works fine ...
o no router ospf
o router ospf
o    network ....
o    default-information originate  #This does not work anymore, which 
can be seen by issueing 'show run': the default-information statement is 
missing.

At this point it seems that there is a workaround by issueing:
o   no default-information originate
o   default-information originate  #'show run' does show the right 
information but it still does NOT work:
At the protocol level the router sends out two messages about 2 seconds 
apart:
- an LS update with LSA type 5. This message is ok. The receiving 
routers will add a default route.
- an LS update with LSA type 1. This message is not ok because the E bit 
(rfc 2328: A.4.2) is not set. The receiving routers will clear their 
previously received default route.

There is a workaround that works and that is:
o no default-information originate
o no router ospf
o router ospf
o    network ...
o    default-information originate
This will always work.

I made a fix in the code (ospfd/ospfd.c) that does solve this problem 
but I don't know if it has side effects.
The fix is to unset the default route distribution after a 'no router 
ospf' command:
==========================================================
*** ospfd.c     2006-01-11 03:00:51.000000000 +0100
--- ospfd.c.patched     2006-08-25 11:30:23.000000000 +0200
***************
*** 391,394 ****
--- 391,395 ----
    for (i = 0; i < ZEBRA_ROUTE_MAX; i++)
      ospf_redistribute_unset (ospf, i);
+   ospf_redistribute_default_unset(ospf);

    for (ALL_LIST_ELEMENTS (ospf->areas, node, nnode, area))
===========================================================

Regards,
Jaap Krabbendam











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