Internet behind a Frame Relay

[Didier Ribbens]

Hello,

To improve my CCNA skills I build a real setup with a Frame Relay and 3 routers (see picture Frame Relay.png)

Everything works , I can ping R1 ; R2 ; R3 and my private home router. (I use OSPF)

I can also ping from R1 any web page , but from R2 and R3 , I can only ping the IP Address I received from my Private Router (192.168.10.28/24)

I have tried to do a quad zero going out on Ser 0/0 or on the IP , but this does not work :(

Any idea what I forgot in my script ?

Best Regards,

Didier

[Peter Paluch]

Hi Didier,

I see a couple of issues with your configuration:

1. On R1, you have ip nat inside and ip nat outside commands applied to its interfaces as if R1 was supposed to do NAT. However, the remainder of the NAT configuration is missing (no ACL, no ip nat inside source command). Therefore, R1 does not currently perform NAT. Is that intentional, or is it an omission?
2. Again on R1 Serial interface, you have used static IP/DLCI mapping but you have defined it only toward R2. The mapping toward R3 is missing. Either define all mappings statically, or do not define them at all. Please note that by default, InverseARP is active and takes care of creating the mappings for you so the use of static mappings is not necessary in your case.
3. Your R2 and R3 definitely need to have a default route. Ideally, as you are running OSPF between R1, R2 and R3, you should configure OSPF on R1 to propagate a default route (I assume that R1 gets its own default route from DHCP). I suggest configuring R1 with the following commands:
   
   ip route 0.0.0.0 0.0.0.0 dhcp ! Makes sure the DHCP default route gets AD 1
   router ospf 1
     default-information originate ! Inject a default route into OSPF
    
4. Most certainly, installing a default route over multipoint Frame Relay interfaces without specifying a next hop address will not work. The problem is that when you say something like
   
   ip route 0.0.0.0 0.0.0.0 Serial0/0/0
   
   with Serial0/0/0 being a Frame Relay interface, the router will start considering the default route as being directly connected. For a directly connected network, the router will attempt to resolve each packet's destination IP address into a DLCI - and of course, because you haven't defined an IP/DLCI mapping for every possible destination IP address, no such mapping will be found and the packet encapsulation will fail. Therefore, it is always recommended to define static routes using next hop addresses. Egress interfaces should be used exclusively if they operate on a point-to-point link layer technology (HDLC, PPP, point-to-point FR subinterfaces, GRE tunnels).

You have not posted the configuration of the Home Router so I cannot comment on that.

Best regards,
Peter

[Didier Ribbens]

Hello Peter,

10000 times Thank You :)

Tonight I have implemented your recommendation and it worked directly.

I had some issues with the DNS server , I was able to ping an IP but not url , but after adding some IP NAME SERVER 8.8.8.8 , it worked directly.

Tomorrow I will try to understand what you recommended me about :

"Either define all mappings statically, or do not define them at all. Please note that by default, InverseARP is active and takes care of creating the mappings for you so the use of static mappings is not necessary in your case"

Again Thank You :)

PS: Attached the 3 working files.

Best Regards,

Didier