[nsp] Setting router ospf passive-interface default

Hudson Delbert J Contr 61 CS/SCBN Delbert.Hudson at LOSANGELES.AF.MIL
Tue Jun 15 12:28:06 EDT 2004


	in ospf, Dijkstra gets to run first, then and only then, are
adjacencies created.
	a link-state change, any change, brings the flood on a need to know
basis as all
	neighbors to the routing process must do the same so that optimum
trees are built.

	so in a word, no. whatever methodology that one might cook up, the
above will happen
unless one were to augment what is pretty much industry standard code. 

	this would violate a tenant of ospf thats all parties must be kept
aware of 
any and all link state changes on networks in which it talks ospf.

	a network is truly defined to its neighbor as the connecting
interface as the
distant end, thus the operations of said interface is of vital importance to

	here's another interesting scenario.

	what if this router is a designated router or bdr.

	i would call  that calls the spf so that ....never mind - just
writing the code right now gives me headache. 

	it would also create devious and more subtle path to hooks for
crackers who use route
poisoning to corrupt routing tables.

	the ospf code or modules would have to modified to accomodate
execution behavior switches
as it needs to know how to execute.

	oh...here's another nightmare, what if you are using ospf as the igp
for bgp.

	route flaps, penalties, soft connection resets, other side gets
stuck in dual if they are
	using eigrp as the ripple becomes a wave.

	imho,	the list of stuff needed to pull this off doessnt resolve
into acceptable trade offs.
rsvp off-line to:piranha @research.suspicious.org


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net]On Behalf Of John Kristoff
Sent: Tuesday, June 15, 2004 8:44 AM
To: cisco-nsp at puck.nether.net
Subject: [nsp] Setting router ospf passive-interface default

Perhaps I've missed something, but is there a way to implement on a
router already running OSPF, where routing interfaces are not going to
be change the following:

  router ospf [process-id]
   passive-interface default

Without having adjacency changes occur?  In my limited testing, either
with a quick copy and paste or tftp upload to the running config, it
seems that either will result in OSPF dropping all interfaces causing
neighbor adjacencies to have to be reestablished.  Since in my example,
the routing interfaces will have 'no passive-interface', routing really
doesn't change so it would be nice if reconvergence didn't have to occur

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