From: Smithson, Brandon K (brandon.k.smithson@citi.com)
Date: Thu Dec 20 2007 - 12:21:25 ART
Hi Bob,
Will you please elaborate on your email? I don't understand how the
last condition, which is "ASBR's next hop interface address falls under
the network range specified in the *router ospf* command" is related to
a "difference in behavior" whether the network range on Router 1's
ethernet interface is 0.0.0.0 or 0.0.0.255 in regards the corner case
documented in Cisco's link below.
In the diagram from Cisco's link below, if the next-hop interface is
Router 1's ethernet interface, what difference does it make if the
network range in the router ospf command is 0.0.0.0 or 0.0.0.255? Both
network ranges enable OSPF on the ethernet interface.
It seems like the first condition and the last condition are the same
for the version they are running (12.2(24a)). For the older version
they are running, don't you have to enable OSPF on the interface by
specifying that network range in the router ospf command? (I understand
you can enable OSPF on an interface with the interface command "ip ospf
x area y", but that requires a newer IOS, which is at least 12.3(11)T
according to the DOC CD.)
The assumption is that the "ASBR's next hop interface" is Router 1's
ethernet interface, NOT Router 100's ethernet interface. The first
condition states:
"OSPF is enabled on the ASBR's next hop interface AND". In this
situation, OSPF is not even enabled on Router 100, so the first
condition reads as if the ASBR's next hop interface has to be Router 1's
ethernet interface.
Thanks,
Brandon
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Bob Sinclair
Sent: Wednesday, December 19, 2007 1:01 PM
To: Gregory Gombas
Cc: ccielab@groupstudy.com
Subject: Re: OSPF network statement
Gregory Gombas wrote:
> I vaguely remember a corner case scenario where the different wildcard
> mask lead to difference in behavior but don't remember the details.
> Maybe someone can chime in here?
>
>
Yes. I believe the corner case you recall is the one regarding the
forwarding address int Type 5 LSAs. It is documented here:
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009
405a.shtml
relating to this issue: "ASBR's next hop interface address falls under
the network range specified in the *router ospf* command."
--Bob Sinclair CCIE 10427 CCSI 30427 www.netmasterclass.net
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