Frame-Relay and end points in different subnets


Frame-Relay and end points in different subnetsOne challenge is frame-relay end points in different subnets, i.e. R1 and R2 are connected via a frame-relay cloud and they have IP addresses of 1.1.1.1/24 and 2.2.2.2/24 respectively. To have these router communicate to each other we have two options for making this scenario works for us.

Frame_Switch_Config

!
frame-relay switching

!
interface Serial1/0
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 frame-relay lmi-type cisco
 frame-relay intf-type dce
 frame-relay route 102 interface Serial1/1 201
 frame-relay route 103 interface Serial1/2 301
!
interface Serial1/1
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 frame-relay lmi-type cisco
 frame-relay intf-type dce
 frame-relay route 201 interface Serial1/0 102
!
interface Serial1/2
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 frame-relay lmi-type cisco
 frame-relay intf-type dce
 frame-relay route 301 interface Serial1/0 103

 

 

1) Use PPP virtual templates to solve the problem.

Lets configure R1

interface Serial1/0
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 no arp frame-relay
 no frame-relay inverse-arp

interface Serial1/0.12 multipoint
 frame-relay interface-dlci 102 ppp Virtual-Template12

interface Virtual-Template12
 ip address 1.1.1.1 255.255.255.0

 

The above configures s1/0 for frame-relay encapsulation, next a multipoint interface is created (this could be a point-to-point or even a physical interface). On the sub interface we map DLCI 102 using ppp to virtual-template 12. On virtual-template 12 IP address 1.1.1.1/24 is assigned.

Next configure R2

interface Virtual-Template21
 ip address 2.2.2.2 255.255.255.0

interface Serial1/0
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 no arp frame-relay
 no frame-relay inverse-arp

interface Serial1/0.21 multipoint
 frame-relay interface-dlci 201 ppp Virtual-Template21

 

R2 is accessible due to the host route in the routing table

R1(config-fr-dlci)#do ping 2.2.2.2

Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 52/82/112 ms

 

 

2) PPP virtual-templates, ip unnumbered and loopbacks.

A second way of solving the problem is placing the IP’s on loopbacks on each end (this is handy because ppp virtual-templates wont take a /32 ip address on the interface.)

In this example R1 will connect to R3 with addresses 10.10.10.1/32 and 3.3.3.3/32

Lets configure R1

interface Serial1/0.13 multipoint
 frame-relay interface-dlci 103 ppp Virtual-Template13

interface Virtual-Template13
 ip unnumbered Loopback0

interface Loopback0
 ip address 10.10.10.1 255.255.255.0

 

 

Next configure R3

interface Loopback0
 ip address 3.3.3.3 255.255.255.0

interface Virtual-Template31
ip unnumbered Loopback0

interface Serial1/0
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 no arp frame-relay
 frame-relay interface-dlci 301 ppp Virtual-Template31
 no frame-relay inverse-arp
 frame-relay lmi-type cisco

Next a ping to the other side is successful.

R3(config-fr-dlci)#do ping 10.10.10.1

Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 76/98/116 ms

 

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About ccie4all
Hello, and welcome to the first post of my CCIE blog This blog has got one simple goal and that is to improve our skills in Cisco Networking field so we can become best engineers on a job market. Wordpress Blog https://ccie4all.wordpress.com/ information about the changes made to Gns3 BGP , MPLS and R&S CCIE labs. In order to access and download all provided materials and receive important updates from Gns3 BGP , MPLS and R&S CCIE labs under GNS3 tab in the main header please go ahead and subscribe to https://ccie4all.wordpress.com/ ! All other posts have not been affected and can be accessed at any given time. Enjoy ! Tom

One Response to Frame-Relay and end points in different subnets

  1. Andrius says:

    Hi

    can you explain why connectivity does not work with different subsets in the first place?

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