Frame Relay routing

[lifebook567]

Can Frame Relay topology do routing like normal IP routing? Form my understanding point-to-point doesn't need any routing because both ends are in the same sub network but what about multi-point? Does it require any routing protocol configuration or Frame-relay switch at service provider side will take care of that using DLCI to route? What is "show frame-relay route"? How it is different than "show ip route"?

[devang_etcom]

show frame-relay route will give you status of DLCI assigned to the interface...

where as show ip route will give show you the routing table which is formed by dynamic routing protocol or may be using the static route...

yes you can use the routing protocols on frame relay routing if you have mutliple point to point interfaces configure on your router then in order to make the reachability between each and every router you need to configure the routing protocols so you can communicate with your host on each interfaces...

rate this post if it helps

regards'

Devang

[globalnettech]

Hello,

in addition to Devang's post, frame relay uses two methods for layer 3 to layer 2 address resolution, inverse arp, or static mapping statements. Both do not involve using any dynamic routing protocol, or static routes. Consider the following scenario, where you have one hub router, and two spoke routers. In order for full connectivity between the three routers, you could configure the following:

Router1 (Hub)

interface Serial0/0

ip address 192.168.123.1 255.255.255.0

encapsulation frame-relay

frame-relay map ip 192.168.1.2 102 broadcast

frame-relay map ip 192.168.1.3 103 broadcast

no frame-relay inverse-arp

Router2 (Spoke)

interface Serial0/0

ip address 192.168.123.2 255.255.255.0

encapsulation frame-relay

frame-relay map ip 192.168.123.1 201 broadcast

frame-relay map ip 192.168.123.3 203 broadcast

no frame-relay inverse-arp

Router3(Spoke)

interface Serial0/0

ip address 192.168.123.3 255.255.255.0

encapsulation frame-relay

frame-relay map ip 192.168.123.1 301 broadcast

frame-relay map ip 192.168.123.2 302 broadcast

no frame-relay inverse-arp

In this example, you would use static mappings on the physical multipoint serial links, in order to achieve full connectivity.

Now, be enabling inverse ARP, the following configuration would establish connectivity from the hub to both spokes (but not from spoke to spoke, since inverse ARP cannot resolve addresses between VCs that are not directly connected):

Router1 (Hub)

interface Serial0/0

ip address 192.168.123.1 255.255.255.0

encapsulation frame-relay

Router2 (Spoke)

interface Serial0/0

ip address 192.168.123.2 255.255.255.0

encapsulation frame-relay

Router3(Spoke)

interface Serial0/0

ip address 192.168.123.3 255.255.255.0

encapsulation frame-relay

A point-to-point link indeed would not need a mapping, since the only destination for any traffic that is being sent on a point-to-point interface is by definiton the device sitting at the other end.

The 'show frame-relay route' command would typically be used on a service provider switch, in order to display all the configured frame relay routes. Check this link for a sample output:

show frame-relay route

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124tcr/twan_r/wan_s1ht.htm#wp1085121

The output would come from service provider interfaces that are configured such as this one:

interface Serial1

description To RouterB

clock rate 2000000

encapsulation frame-relay

frame-relay intf-type dce

frame-relay route 201 interface Serial0 102

frame-relay route 203 interface Serial0 203

frame-relay route 213 interface Serial0 213

frame-relay route 204 interface Serial0 204

frame-relay route 205 interface Serial0 205

If you are interested, have a look at this link, which describes how to build a compound frame-relay switch, by using Cisco (2500) routers:

Building a Compound Frame Relay Switch

http://www.internetworkexpert.com/resources/compound.frame-relay.htm

Regards,

GNT