Table Of Contents
OSPF Point-to-Multipoint Network
with Separate Costs per NeighborSpecify a Neighbor's Cost on Point-to-Multipoint, Broadcast Networks
Configure an Interface as Point-to-Multipoint, Nonbroadcast
OSPF Point-to-Multipoint, Broadcast
OSPF Point-to-Multipoint, Nonbroadcast
OSPF Point-to-Multipoint Network
with Separate Costs per Neighbor
Description
OSPF has two new features related to point-to-multipoint networks. One feature applies to broadcast networks; the other feature applies to nonbroadcast networks.
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On point-to-multipoint, broadcast networks, there is no need to specify neighbors. However, you can specify neighbors with the neighbor command, in which case you should specify a cost to that neighbor.
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Before this feature, some OSPF point-to-multipoint protocol traffic was treated as multicast traffic. Therefore, the neighbor command was not needed for point-to-multipoint interfaces because multicast took care of the traffic. Hellos, updates and acknowledgments were sent using multicast. In particular, multicast hellos discovered all neighbors dynamically.
However, some customers were using point-to-multipoint on nonbroadcast media (such as classic IP over ATM), so their routers could not dynamically discover their neighbors. This feature allows the neighbor command to be used on point-to-multipoint interfaces.
On any point-to-multipoint interface (broadcast or not), the Cisco IOS software assumed the cost to each neighbor was equal. The cost was configured with the ip ospf cost command. In reality, the bandwidth to each neighbor is different, so the cost should be different. With this feature, you can configure a separate cost to each neighbor. This feature applies to point-to-multipoint interfaces only.
Benefits
You can now configure neighbors on point-to-multipoint interfaces and assign a cost to each neighbor. These capabilities allow the router to dynamically discover neighbors over nonbroadcast media and to prefer some routes over others by assigning different costs to neighbors.
Platforms
This feature is supported on these platforms:
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Configuration Tasks
This section describes the following tasks to configure OSPF point-to-multipoint interfaces. Perform one of these tasks, depending on whether your network is broadcast or nonbroadcast.
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Specify a Neighbor's Cost on Point-to-Multipoint, Broadcast Networks
To treat an interface as point-to-multipoint broadcast and assign a cost to each neighbor, perform the following tasks beginning in interface configuration mode:
Configure an Interface as Point-to-Multipoint, Nonbroadcast
To treat the interface as point-to-multipoint when the media does not support broadcast, perform the following task in interface configuration mode:
Configuration Examples
This section includes the following configuration examples:
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OSPF Point-to-Multipoint, Broadcast
The following example illustrates a point-to-multipoint network with broadcast.
interface Serial0ip address 10.0.1.1 255.255.255.0encapsulation frame-relayip ospf cost 100ip ospf network point-to-multipointframe-relay map ip 10.0.1.3 202 broadcastframe-relay map ip 10.0.1.4 203 broadcastframe-relay map ip 10.0.1.5 204 broadcastframe-relay local-dlci 200!router ospf 1network 10.0.1.0 0.0.0.255 area 0neighbor 10.0.1.5 cost 5neighbor 10.0.1.4 cost 10The configuration of the neighbor at 10.0.1.3 is:
interface $core2s2ip address 10.0.1.3 255.255.255.0ip ospf network point-to-multipointencapsulation frame-relayframe-relay local-dlci 301frame-relay map ip $core7s0_ip 300 broadcastno shut!router ospf 1network 10.0.1.0 0.0.0.255 area 0The output shown for neighbors in the first configuration above looks like this:
Router# show ip ospf neighborNeighbor ID Pri State Dead Time Address Interface4.1.1.1 1 FULL/ - 00:01:50 10.0.1.5 Serial03.1.1.1 1 FULL/ - 00:01:47 10.0.1.4 Serial02.1.1.1 1 FULL/ - 00:01:45 10.0.1.3 Serial0The route information in the first configuration above looks like this:
Router# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate defaultU - per-user static route, o - ODRGateway of last resort is not setC 1.0.0.0/8 is directly connected, Loopback010.0.0.0/8 is variably subnetted, 4 subnets, 2 masksO 10.0.1.3/32 [110/100] via 10.0.1.3, 00:39:08, Serial0C 10.0.1.0/24 is directly connected, Serial0O 10.0.1.5/32 [110/5] via 10.0.1.5, 00:39:08, Serial0O 10.0.1.4/32 [110/10] via 10.0.1.4, 00:39:08, Serial0OSPF Point-to-Multipoint, Nonbroadcast
The following example illustrates a point-to-multipoint network with nonbroadcast.
interface Serial0ip address 10.0.1.1 255.255.255.0ip ospf network point-to-multipoint non-broadcastencapsulation frame-relayno keepaliveframe-relay local-dlci 200frame-relay map ip 10.0.1.3 202frame-relay map ip 10.0.1.4 203frame-relay map ip 10.0.1.5 204no shut!router ospf 1network 10.0.1.0 0.0.0.255 area 0neighbor 10.0.1.3 cost 5neighbor 10.0.1.4 cost 10neighbor 10.0.1.5 cost 15The following is the configuration for the router on the other side:
interface Serial9/2ip address 10.0.1.3 255.255.255.0encapsulation frame-relayip ospf network point-to-multipoint non-broadcastno ip mroute-cacheno keepaliveno fair-queueframe-relay local-dlci 301frame-relay map ip 10.0.1.1 300no shut!router ospf 1network 10.0.1.0 0.0.0.255 area 0The output shown for neighbors in the first configuration above looks like this:
Router# show ip ospf neighborNeighbor ID Pri State Dead Time Address Interface4.1.1.1 1 FULL/ - 00:01:52 10.0.1.5 Serial03.1.1.1 1 FULL/ - 00:01:52 10.0.1.4 Serial02.1.1.1 1 FULL/ - 00:01:52 10.0.1.3 Serial0Command Reference
This section documents modified commands. All other commands used with this feature are documented in the Cisco IOS Release 11.3 command references.
ip ospf network
To configure the OSPF network type to a type other than the default for a given media, use the ip ospf network interface configuration command. To return to the default value, use the no form of this command.
ip ospf network {broadcast | non-broadcast | {point-to-multipoint [non-broadcast]}}
no ip ospf networkSyntax Description
Default
Depends on the network type.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0. The point-to-multipoint keyword first appeared in Cisco IOS Release 10.3. The non-broadcast keyword used with the point-to-multipoint keyword first appeared in Cisco IOS Release 11.3 AA.
Using this feature, you can configure broadcast networks as nonbroadcast multiaccess (NBMA) networks when, for example, you have routers in your network that do not support multicast addressing. You can also configure nonbroadcast multiaccess networks (such as X.25, Frame Relay, and SMDS) as broadcast networks. This feature saves you from having to configure neighbors.
Configuring NBMA networks as either broadcast or nonbroadcast assumes that there are virtual circuits from every router to every router or fully meshed network. This is not true for some cases, for example, because of cost constraints or when you have only a partially meshed network. In these cases, you can configure the OSPF network type as a point-to-multipoint network. Routing between two routers that are not directly connected will go through the router that has virtual circuits to both routers. You do not need to configure neighbors when using this feature.
If this command is issued on an interface that does not allow it, it will be ignored.
OSPF has two features related to point-to-multipoint networks. One feature applies to broadcast networks; the other feature applies to nonbroadcast networks.
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Examples
The following example sets your OSPF network as a broadcast network:
interface serial 0 ip address 160.89.77.17 255.255.255.0ip ospf network broadcastencapsulation frame-relayThe following example illustrates a point-to-multipoint network with broadcast.
interface Serial0ip address 10.0.1.1 255.255.255.0encapsulation frame-relayip ospf cost 100ip ospf network point-to-multipointframe-relay map ip 10.0.1.3 202 broadcastframe-relay map ip 10.0.1.4 203 broadcastframe-relay map ip 10.0.1.5 204 broadcastframe-relay local-dlci 200!router ospf 1network 10.0.1.0 0.0.0.255 area 0neighbor 10.0.1.5 cost 5neighbor 10.0.1.4 cost 10Related Commands
frame-relay map
neighbor (OSPF)
x25 mapneighbor (OSPF)
To configure OSPF routers interconnecting to nonbroadcast networks, use this form of the neighbor router configuration command. To remove a configuration, use the no form of this command.
neighbor ip-address [priority number] [poll-interval seconds] [cost number]
no neighbor ip-address [priority number] [poll-interval seconds] [cost number]Syntax Description
Default
No configuration is specified.
Command Mode
Router configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0. The cost keyword was added in Release 11.3 AA.
X.25 and Frame Relay provide an optional broadcast capability that can be configured in the map to allow OSPF to run as a broadcast network. At the OSPF level you can configure the router as a broadcast network. See the x25 map and frame-relay map commands in the "X.25 Commands" and "Frame Relay Commands" chapters, respectively, in the Wide-Area Networking Command Reference for more detail.
One neighbor entry must be included in the Cisco IOS software configuration for each known nonbroadcast network neighbor. The neighbor address has to be on the primary address of the interface.
If a neighboring router has become inactive (hello packets have not been seen for the Router Dead Interval period), it may still be necessary to send hello packets to the dead neighbor. These hello packets will be sent at a reduced rate called Poll Interval.
When the router first starts up, it sends only hello packets to those routers with non-zero priority; that is, routers that are eligible to become designated routers (DR) and backup designated routers (BDR). After DR and BDR are selected, DR and BDR will then start sending hello packets to all neighbors in order to form adjacencies.
Prior to Release 12.0, the neighbor command applied to NBMA networks only. With Release 12.0, the neighbor command applies to NBMA networks and point-to-multipoint networks. On NBMA networks, the cost keyword is not accepted.
Examples
The following example declares a router at address 131.108.3.4 on a nonbroadcast network, with a priority of 1 and a poll interval of 180 seconds:
router ospf neighbor 131.108.3.4 priority 1 poll-interval 180The following example illustrates a point-to-multipoint network with nonbroadcast.
interface Serial0ip address 10.0.1.1 255.255.255.0ip ospf network point-to-multipoint non-broadcastencapsulation frame-relayno keepaliveframe-relay local-dlci 200frame-relay map ip 10.0.1.3 202frame-relay map ip 10.0.1.4 203frame-relay map ip 10.0.1.5 204no shut!router ospf 1network 10.0.1.0 0.0.0.255 area 0neighbor 10.0.1.3 cost 5neighbor 10.0.1.4 cost 10neighbor 10.0.1.5 cost 15Related Commands
ip ospf network
ip ospf priority
Guest