Hub and spoke frame relay

[leowchongwei]

Hi,

Between the following 2 configuration of a hub and spoke frame relay, what are the pro and cons???

Eg 1

interface serial 0

encapsulation frame-relay

interface serial 0.1 point-to-point

ip address 10.1.1.1 255.255.255.0

frame-relay interface dlci 100

interface serial 0.2 point-to-point

ip address 10.1.2.1 255.255.255.0

frame-relay interface dlci 200

Eg 2

interface serial 0

encapsulation frame-relay

interface serial 0.1 multipoint

ip address 10.1.1.1 255.255.255.0

frame-relay map 10.1.1.2 100 broadcast

interface serial 0.2 multipoint

ip address 10.1.2.1 255.255.255.0

frame-relay map 10.1.2.2 200 broadcast

[gleithner]

I was curious about this as I'd recalled reading about this scenario in Doyles Routing TCP/IP. Multipoints are treated by ISIS as a LAN, p2p's as a p2p, so the only caveat is that if you go multipoint it has to be multipoint on each router, just as it is in msdonahue's configuration(Spoke 1 frame relay on the physical interface treated as multipoint)

If you used p2p at the spoke you'll have to use p2p at the hub. This is different then OSPF where i've used a variety of different types of int and sub-int's(with appropriate ip ospf network types and/or hello/dead parameter changes).

[gleithner]

Firstly, Eg2 doesn't need two multipoint subinfs if it's going to be the hub. You can use one multipoint subif, and all your spokes can be on the same subnet(since multipoint doesn't require diff subnets). Also, you don't need the map statements, use interface dlci instead and InvARP will take care of the rest.

So eg2 could be

interface serial 0.1 multipoint

ip address 10.1.1.1 255.255.255.0

frame-relay interface-dlci 100

frame-relay interface-dlci 200

However, as already stated, multipoint interfaces have other configuring issues with your routing protocols.

Since you could just use VLSM to make small subnets, P2P is probably the way to go. Although with a large number of spokes you'll have to configure each p2p int on the hub.