frame relay configuration question!

Unanswered Question
Feb 22nd, 2008

Hi all,

I would like to know what are the differences and benefits of using this configuration on a fr interface?

When I should use this one ?

interface Serial0/1/0

ip address 10.18.251.74 255.255.255.252

encapsulation frame-relay IETF

frame-relay interface-dlci 16

frame-relay lmi-type cisco

OR use this one?

interface Serial0/1/0

description Circuito xxxx

no ip address

encapsulation frame-relay IETF

no ip mroute-cache

load-interval 30

serial restart-delay 0

frame-relay lmi-type cisco

!

interface Serial0/0/1.16 point-to-point

description Conexion ISP

bandwidth 1920

ip address 10.18.251.74 255.255.255.252

ip verify unicast reverse-path

no ip redirects

no ip unreachables

no ip proxy-arp

ip virtual-reassembly

frame-relay interface-dlci 16 IETF

What are the benefits?

Thanks

Regards

Lp

I have this problem too.
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Mohamed Sobair Fri, 02/22/2008 - 11:35

Hi,

On the main interface you could have Multiple VCs connected to the same hub.

In a point-to-point frame-relay, you just limiting it to one PVC between two DTEs.

HTH

Mohamed

Richard Burts Fri, 02/22/2008 - 12:33

Lp

I would like to add a little to the answer given by Mohamed. Your first configuration which uses the physical interface is inherently a multipoint Frame Relay connection - even if there is only a single PVC it will be treated as multipoint. Your second configuration is explicitly a point to point Frame Relay interface. Which one you should use will depend on some aspects of the design of your network. If the design is for multipoint then the first configuration is what to use and if the design is for point to point then the second configuration is the one to use.

Beyond the fact that there might be several PVCs or only a single PVC there are some differences in how the two configurations will work. In a multipoint interface there will be some Frame Relay mapping which may be manually configured or the IOS can dynamically discover it. In multipoint all the interface addresses on all the routers on the PVCs will be in a single subnet. In point to point each PVC will be a unique subnet.

The operation of routing protocols may be a bit different depending on whether the interface is multipoint or point to point. OSPF establishes neighbor relationships differently depending on whether it is multipoint or point to point. EIGRP enforces split horizon on multipoint which is not a factor in point to point.

HTH

Rick

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