From: Snow, Tim (timothy.snow@eds.com)
Date: Tue Oct 07 2003 - 20:43:57 GMT-3
1 - The "ip ospf network point-to-multipoint" dictates that sub-int should
be treated as a collection of point-to-point interfaces (no DR here!!)
2 - see point 1, I don't think it's a matter of "better". I think it
depends on what your doing.
3 - The "non-broadcast" function of the "ip ospf network
point-to-multipoint" just changes the way the interface functions. Rather
than send out multicast hellos, if you use the "non-broadcast" keyword then
you need to statically define your neighbors.
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr
_c/ipcprt2/1cfospf.htm#1001079
Before the point-to-multipoint keyword was added to the ip ospf network
interface configuration command, some OSPF point-to-multipoint protocol
traffic was treated as multicast traffic. Therefore, the neighbor router
configuration command was not needed for point-to-multipoint interfaces
because multicast took care of the traffic. Hello, update, and
acknowledgment messages were sent using multicast. In particular, multicast
hello messages discovered all neighbors dynamically.
4 - You can't use "distribute-list" like you can with DV protocols as each
neighbor has to have a consistent view of the LSDB. However, if you want to
filter from the OSPF LSDB into the RT then you'd use the "distribute-list
in" option. Keep in mind that only filters from the local RT and other
routers will need to have this done as well, if that is your goal to get
that router out of all the RT's.
5 - When you redistribute routes into OSPF, they default to E2 with a metric
of 20. Therefore, you don't need to specify a default metric.
I suggest you test this out and get very familiar with the way OSPF works
rather than just knowing the theory behind it.
Tim
#12042
-----Original Message-----
From: Yasser Aly [mailto:blackyeyes00@hotmail.com]
Sent: Tuesday, October 07, 2003 3:35 PM
To: ccielab@groupstudy.com
Subject: Some OSPF thoughts
Dear All,
I have some OSPF questions and hope to find answers to
1- Why the " ip ospf network point-to-multipoint " was invented ? Shouldn't
the " ip ospf network broadcast" takecare of NBMA networks problem and form
adjacency?
2- When trying to solve the NBMA problem when it is better to use the
broadcast network type versus the point-to-multipoint type, versus stating
the neighbors explicitly ?
3- What is the situation would where I need to use " ip ospf network
point-to-multipoint non-broadcast " ?
4- In OSPF. Why distribute-list is always applied on in direction and not
the out ?
5- When distributing routes into OSPF, Is is mandatory to use the "
default-metric "command or redistribution can be done without using this
command
Regards,
Yasser
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