frame relay types and MPLs

Posted on 2011-03-14
Last Modified: 2012-05-11
1-if I understand FR means there is a a hub and spokes topolgy. Correct?
2- when configuring FR, usually from the HUB , if the configuration  is ethernet, it defaults to non-broadcast. Correct? in this case can we configure sub-interfaces for a physical ethernet interface? or sub-interfaces apply only to serial interfaces?
3-  when configuring IP OSPF network on interface,
as I mentionned on point 1.
-if it's  serial int it will default to NBMA
-if it's ethernet it will default to Broadcast
but if we select point to multipoint, it will also give us extra option to make it NBMA or Broadcast.

any one to clear this up?

4 I also want to know which one is commonly used nowadays FR or MPLS? and the reason?

Question by:jskfan
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Accepted Solution

Don Johnston earned 334 total points
ID: 35133396
1) No. The "topology" is what you want.
2) Frame-Relay is a layer-2 protocol (As is ethernet).
3) There is no layer-2 broadcast in frame-relay. However, it's possible for a protocol that uses broadcast (or multicast) in a frame-relay environment. The router simply makes copies of packets and sends them out on the different DLCI's.
4) Frame-Relay has been around for 20 years. There's a lot of frame-relay still in use. MPLS is relatively new. So on the whole, there are probably more frame-relay connections than there are MPLS. BUT... frame-relay is a dying protocol. Many of the frame-relay providers have stopped offering service to new customers (if you're an existing customer, you can add circuits). This makes certification somewhat frustrating. Some of the Cisco certs require knowledge of Frame-Relay. But in the real world, there's less and less of it.
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Assisted Solution

Otto_N earned 166 total points
ID: 35139420
To add to Don's comments:

1) If you connect to a Frame-Relay network (Frame-Relay switched connected to each other), you can create various circuits between any entry points.  However, a full-meshed topology quickly becomes expensive to expand (if you pay per circuit), which is why most implementations used the hub-and-spoke topology.  However, it is also possible to configure frame-relay encapsulation over simple serial point-to-point links, if you have the need to have different sub-interfaces.

2) You are not able to configure frame-relay encapsulation over Ethernet:  Frame-relay is only applicable on serial interfaces (as far as I'm aware).  Sub-interfaces is possible on Ethernet, but this uses 802.1Q trunking (or the older Cisco-proprietary ISL) to tag frames withparticular VLAN-ID.

3) OSPF on Serial interfaces using frame-relay, X.25 and ATM will default to NBMA, but if it uses point-to-point encapsulations (like PPP and HDLC) it will default to point-to-point mode.  Since Ethernet does have broadcast capability, it will aoutomatically join the defined multicast group, and does not need any special treatment.  In fact, Im not even sure that you can change it to any other mode.

4) As Don said: FR might be more at this stage, but MPLS is rapidly gaining, and will overtake FR pretty soon, if it hasn't already done so.

Author Comment

ID: 35150956
FR configuration involves the administrator.
I wonder if MPLS involves the Administrator in regards to configuration or it is taken care by the FR provider
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Assisted Solution

by:Don Johnston
Don Johnston earned 334 total points
ID: 35152576
Frame-Relay and MPLS are both services that are offered by a provider.

Both services require configuration on the customer equipment.

Author Closing Comment

ID: 35293100

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