frame relay

[carl_townshend]

hi all, can anyone tell me why there is an option of creating multipoint in frame relay, why not just create seperate subinterfaces and use point to point links ?

[devang_etcom]

its all depend on your requirement look here:

Point-to-point subinterface?With point-to-point subinterfaces, each pair of routers has its own subnet. If you put the PVC on a point-to-point subinterface, the router assumes that there is only one point-to-point PVC configured on the subinterface. Therefore, any IP packets with a destination IP address in the same subnet are forwarded on this virtual circuit (VC). This is the simplest way to configure the mapping and is therefore the recommended method.

Multipoint networks?Multipoint networks have three or more routers in the same subnet. If you put the PVC in a point-to-multipoint subinterface or in the main interface (which is multipoint by default), you need to either configure a static mapping or enable inverse Address Resolution Protocol (ARP) for dynamic mapping.

rate this post if it helps

regards

Devang

[carl_townshend]

so do you still configure static mapping on the point to point interface also ?, i have seen on configs where they put a dlci on one and and reverse it on the other, is this necessary ? as i thought the dlci was only locally significant

[globalnettech]

Hello,

point-to-point interfaces do not need a static mapping (a Layer 3 to Layer 2 protocol resolution), since the only destination for any traffic sent out on a point-to-point interface is the device residing on the other end of the link. The configs you are referring to are actually general practice by ISP's. Let's say you have a frame-relay link from Router 12 to Router 13, the ISP would usually number the DLCI on Router 12 '1213' and the DLCI on Router 13 '1312'. Although it is true that the DLCI is only locally significant, it still needs to be mapped by the ISP (the mapping occurs in the ISP frame relay switches).

Does that make sense ?

Regards,

GNT

[carl_townshend]

yes im with you, wouldnt it be 3121, i though you reverse them, also can you give me an example of the point to point, do you just type the dlci number in, without a map ?

[jackyoung]

Normally, yes, just require a DLCI no. and correct IP address assignement is fine.

Hope this helps.

[carl_townshend]

thanks Jack

just to finish, when using point to point do you always reverse the dlci's either end ? or is this up to the provider ?

[jackyoung]

The DLCI no. is provided from the service provider, we cannot request it.