From: Weidong Xiao (Weidong.Xiao@vi.net)
Date: Wed Dec 03 2003 - 06:53:01 GMT-3
Hi Brian,
What puzzles me is that:
under frame-relay interface, config 'ip ospf network point-to-multipoint' without the 'non-broadcast' key-word, then under 'router ospf 1', I still can config 'neighbor xxxx cost yyyy'.
So what's the point to have a non-broadcast key-word? Is it that I can config costs doesn't mean the costs take effect?
interface Serial0/1
no ip address
encapsulation frame-relay
interface Serial0/1.1 multipoint
ip address 192.168.20.1 255.255.255.0
ip ospf network point-to-multipoint <----NO 'non-broadcast'
router ospf 1
network 192.168.20.1 0.0.0.0 area 0
neighbor 192.168.20.3 cost 3900
neighbor 192.168.20.2 cost 3000
Thank you very much,
Weidong
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Brian Dennis
> Sent: 01 December 2003 19:34
> To: 'Ahmed'; ccielab@groupstudy.com
> Subject: RE: Point-to-Multipoint non-broadcast command
>
>
> OSPF point-to-multipoint non-broadcast will allow you
> to assign the
> cost on a per neighbor basis as opposed to using the
> interface's cost. This
> is useful on a multipoint Frame Relay interface where there are two
> neighbors advertising the same route but the CIRs for the
> DLCIs to reach
> each neighbor is different. Or these two neighbors that are
> advertising the
> same route have different port speeds to the Frame Relay
> network. Remember
> that the cost is based on your incoming interface's bandwidth
> and not the
> bandwidth of the neighbor's interface that connects to you.
>
> Say we have two remote routers over Frame Relay and the remote
> routers are both connected to and advertising the same
> Ethernet segment.
> Our router is connected to these two routers via Frame Relay.
> One of the
> remote routers has a T1 Frame Relay connection and the other
> has a 64k Frame
> Relay connection. Since our cost to the Ethernet segment
> advertised by
> these two routers will be calculated based on the cost of the Ethernet
> segment plus the cost of our incoming interface, both routes
> appear to be
> equal cost. Obviously this is not what we would want. We
> would want to
> prefer the route from the router with the T1 connection over the 64k
> connection.
>
> Here is an example with two remote routers advertising the
> same network
> (loopback interfaces):
>
> Rack2R4#show ip ospf interface s0/0 | include Cost
> Process ID 1, Router ID 150.1.4.4, Network Type
> POINT_TO_MULTIPOINT, Cost:
> 64
> Rack1R4#sho run int s0/0
> interface Serial0/0
> ip address 154.1.0.4 255.255.255.0
> encapsulation frame-relay
> ip ospf network point-to-multipoint
> frame-relay map ip 154.1.0.3 403 broadcast
> frame-relay map ip 154.1.0.5 405 broadcast
> no frame-relay inverse-arp
> end
> Rack2R4#sho ip route 150.1.0.0 255.255.255.0
> Routing entry for 150.1.0.0/24
> Known via "ospf 1", distance 110, metric 65, type intra area
> Last update from 154.1.0.3 on Serial0/0, 00:00:30 ago
> Routing Descriptor Blocks:
> * 154.1.0.3, from 150.1.3.3, 00:00:30 ago, via Serial0/0
> Route metric is 65, traffic share count is 1
> 154.1.0.5, from 150.1.5.5, 00:00:30 ago, via Serial0/0
> Route metric is 65, traffic share count is 1
>
> Rack2R4#
>
> As you can see both 154.1.0.3 (router-ID 150.1.3.3) and
> 154.1.0.5
> (router-ID 150.1.5.5) are advertising the 150.1.0.0/24
> network with an OSPF
> cost of 1 (total cost minus our interface's cost, 65-64=1).
> If both of
> these routers have the same port speed to the Frame Relay
> network then this
> is what we would want to see, two equal cost paths. But if they have
> different port speeds, then we would want to prefer the route from the
> router with the higher port speed, theoretically. The
> problem is that OSPF
> does not take into account the cost of the remote router's
> interface to us.
> We only take into account the cost of the loopback and our
> interface's cost
> to reach the remote neighbor.
>
> To prefer the route from the router with the higher
> port speed, we
> are going to use OSPF point-to-multipoint non-broadcast to
> specify the cost
> on a per neighbor basis. In this example we are going to add
> a cost of 25
> to the routes from 154.1.0.5 and 50 to the routes from 154.1.0.3.
>
> Rack1R4#sho run | be router ospf
> router ospf 1
> network 154.1.0.0 0.0.255.255 area 0
> neighbor 154.1.0.5 cost 25
> neighbor 154.1.0.3 cost 50
> Rack1R4#sho run int s0/0
> interface Serial0/0
> ip address 154.1.0.4 255.255.255.0
> encapsulation frame-relay
> ip ospf network point-to-multipoint non-broadcast
> frame-relay map ip 154.1.0.3 403 broadcast
> frame-relay map ip 154.1.0.5 405 broadcast
> no frame-relay inverse-arp
> end
> Rack1R4#sho ip route 150.1.0.0 255.255.255.0
> Routing entry for 150.1.0.0/24
> Known via "ospf 1", distance 110, metric 26, type intra area
> Last update from 154.1.0.5 on Serial0/0, 00:06:13 ago
> Routing Descriptor Blocks:
> * 154.1.0.5, from 150.1.5.5, 00:06:13 ago, via Serial0/0
> Route metric is 26, traffic share count is 1
> ^^^^^^^^^^^^^^^^^^^
>
> Now we can see that we prefer the route from 154.1.0.5 (router-ID
> 150.1.5.5).
>
> Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
> bdennis@internetworkexpert.com
> Toll Free: 877-224-8987
> Direct: 775-745-6404 (Outside the US and Canada)
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of
> Ahmed
> Sent: Saturday, November 29, 2003 7:40 PM
> To: ccielab@groupstudy.com
> Subject: Point-to-Multipoint non-broadcast command
>
> What is the reason for the command "POINT-TO-MULTIPOINT
> NON-BROADCAST" in
> an OSPF over Frame-Relay environment? I read the document on
> CCO, but was
> not very clear. Can someone please explain it with the
> example? Thanks,
> Ahmed
>
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