Point-to-Multipoint concept

[zillah2004]

I just want to verify my understanding for this :

Cisco says:

((Multipoint - A single multipoint subinterface (zillah says: this shouldn't be interface instead of subinterface ?) is used to establish multiple PVC connections to multiple physical interfaces or subinterfaces on remote routers. All the participating interfaces would be in the same subnet)).

Now we have got multiple subinterfaces ( within one hub ) that connect to multiple end points (more than one spokes).

now does the term “ point-to-multipoint “ meant to be like this :

1- “Point----“ refers to hub which has multiple subinterfaces

2- “-----Multipoint” refers to spokes (more than one) that have only one interface or subinterface in most cases

Or it meant to be like this :

1- “Point----“ refers to spoke that has only one interface or subinterface in most cases.

2- “-----Multipoint” refers to hub that has multiple subinterfaces or one interface with multiple DLCIs

I mean the term “point-to-multipoint” does refer to device itself (i.e “point we” have one hub , and multipoint we have more that one remote nodes or points ) or it does refer to the interfaces .

[pkhatri]

It refers to interfaces.

Here's an example:

- a hub with 3 PVCs configured under the same interface. This interface is configured as a multipoint interface. The term multipoint here means that this interface connects to multiple devices. So when you say point-to-multipoint, the point refers to the hub's interface, and the multipoint refers to the three other routers it is connected to.

- a hub with 3 PVCs with each PVC configured under its own sub-interface. In this case, the interface will be considered a point-to-point interface as each interface connects to a single router.

Paresh/.

[zillah2004]

((It refers to interfaces))

That means the word "multipoint" refer to the HUB, because Hub has got more than one PVCs in most cases (in your example 3 PVCs). Then you said :"the point refers to the hub's interface"

"The term multipoint here means that this interface connects to multiple devices"

My understanding to your explaination, because a hub's physical interface can have more than one PVCs and each PVC will be connected to one spoke.

[zillah2004]

Any comment, thanks

[coolboarderguy]

Hi All,

yes, exactly, the router(hub) can have multiple connections(relationships) to multiple routers(spokes)on the one interface, hence mulitipoint-to-point

ex.

Router A = Hub

Rouers B, C, D, E, F etc are all connected to Router A(one connection each for them) and Router A has 5 connections to it's one interface(via sub-interfaces). HTH. Cheers.

coolboarderguy.

[pkhatri]

I meant that the interface on the hub is considered the multipoint interface because it connects to multiple other devices.

So, you can have interfaces on the same router that are:

- multipoint - if there are multiple PVCs on that interface

- point-to-point - if there is a single PVC on the interface

Paresh

[ekiriakos]

Hi Zillah,

I think your original question asked about p-2-p and multipoint and then you introduced the concept of point-to-multipoint. I think you may be confuding Frame relay p-2-p and multipoint interfaces with the ospf network type point-to-multipoint.

As rightly explaind by other people a physical frame relay interface is Multipoint. A subinterface can be either a point-to-point or multipoint (behaves like a physical interface). Normally a point-to-point link is used when two devices share the same subnet, whilst multipoint may have multiple devices on the same subnet. For example a HUB may connect to multiple Spokes (pvc to each spoke) and they all share the same subnet.

Point-to-multipoint is associated with an OSPF network type. This network type does not require a DR election (unlike Broadcast and NON-Broadcast ospf networks where a DR is required). For more info on ospf network types try:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfospf.htm#wp1001760

HTH

E.

[zillah2004]

((I think your original question asked about p-2-p and multipoint----))

Yes I get confused, and when you raised this hint, I checked cisco curriculum again,,,,,CCNA4 V3.1 Cisco says under this article (5.2.4 Frame Relay subinterfaces):

"Frame Relay subinterfaces can be configured in either point-to-point or multipoint mode:

Multipoint - A single multipoint subinterface is used to establish multiple PVC connections to multiple physical interfaces or subinterfaces on remote routers. All the participating interfaces would be in the same subnet. The subinterface acts like an NBMA Frame Relay interface so routing update traffic is subject to the split-horizon rule"

router(config-if)#interface serialnumber.subinterface-number [multipoint | point-to-point]---As we can see the configuration with physical layer, not with routing OSPF routing protocol as we have done below

((with the ospf network type point-to-multipoint))

I think you are right as cisco CCNP1 curriculum explained that under OSPF module,,,,,,, (6.4.4 Point-to-Multipoint OSPF ) says:

"In a point-to-multipoint network, a hub router is directly connected to multiple spoke routers, but all the WAN interfaces are addressed on the same subnet"

ip ospf network point-to-multipoint-----As we can see the configuration of point-to-multipoint with routing protocol not with physical layer as we have done above with a Frame-Relay

[zillah2004]

(((I think your original question asked about p-2-p and multipoint and then you introduced the concept of point-to-multipoint. I think you may be confuding Frame relay p-2-p and multipoint interfaces with the ospf network type point-to-multipoint.

)))

The reason for my confusion was this:

http://www.steampacketradio.com/solutions/config/point_to_multi_point.htm

Note: in the link above it has been written like this:"Point to Multi-Point" while in cisco it has been written like this :point-to-multipoint,,,,,Have these been written intentionally ?

[ekiriakos]

Completely different concept. This link talks about wireless bridge modes in a point to point or point to multipoint configuration. If you want to understand this concept I suggest further reading on WLANs.

Rgds

E.