Friday, July 30, 2010

Frame-Relay Challenge 1 - Solve The Puzzle

So welcome back everyone and here is the first puzzle which I am posting for blog followers today. Up-till now I was showing up various scenarios with explanation and required configs & other details.

But today I want to add some more fun here for you guys. So here is a great frame-relay challenge for you guys which I solved recently sent by one friend. And of-course this scenario got so much to teach you and test your frame-relay skills. To solve this scenario you would need to recall all frame relay basics. At-least that's what I feel honestly.

One last thing as surprise package is - the first guy who will post the correct solution as per requirements will get a surprise CCIE R&S preparation material from me in free. :-)

I'll wait till 5 PM IST Monday evening before I post the correct solution here. So good luck as you have plenty of time for such small but still interesting task to be solved & have a nice weekend ahead.

Here are the quick requirements with Detailed Diagram. 

1.> Configure a partially meshed Frame-Relay network between Router R1, R2, R3 & R4 Using DLCI information given in the diagram

2.> Don't use subinterfaces on R1, R2 & R3

3.> Use Sub-interface on .1 on R4 eg - s0/0.1

4.> Don't use any dynamic Frame-Relay mappings anywhere

5.> Don't use any Static Frame-Relay mappings on R4

6.> Traffic From R2 destined for R4 should transit R1

7.> All other traffic should take the most direct path through Frame-Relay network

Note:- No Extra Configs should be put unless otherwise specified, all router should have full reach-ability (including self interfaces), no redundant broadcast should be occurring on any of DLCIs.

For those who want to test this topology on GNS and are little new to Frame-Relay Switch  configurations over GNS. Here is a quick screen shot for you of  FR Switch Mappings:

And of course you can send me your solution directly through email at  -

And at last but not least....Don't just freak out in the middle while solving this :-)

Sunday, July 11, 2010

CCIE R&S Version 4 Lab Demo - By Cisco

If you are pursuing CCIE R&S ver 4 and ever been interested to see it's demo to get the feel of environment of Giant CCIE R&S lab exam then here is a gr8 URL for you to get that feel :-)

Deepak Arora

Friday, July 9, 2010

Tuesday, July 6, 2010

Finding An Unknown AS Number Of BGP Peer - Who's behind the mask ?

Here is another CCIE Lab tip. This is another trick which I learned recently. In real world we probably don't need to learn this and this is obviously not a practical situation but here is that quick task: You need to peer with a BackBone(BB) router in order to learn tons of routes but you don't know AS number of BB router in order to peer with it. On the other hand BB router is configured properly in order to send those routes to it's peers.

Lets start with very basic config before solving this puzzle.

*      Basic Config         *

R1(config)#do sh ip int b | e do
Interface            IP-Address      OK? Method Status Protocol
FastEthernet0/0      YES manual up      up
Loopback0       YES manual up      up

R1(config)#do sh prot | e do
Global values:
  Internet Protocol routing is enabled
FastEthernet0/0 is up, line protocol is up
  Internet address is
Loopback0 is up, line protocol is up
  Internet address is

R2(config)#do sh ip int b | e do
Interface          IP-Address      OK? Method Status  Protocol
FastEthernet0/0      YES manual up      up
Loopback0     YES manual up      up

R2(config)#do sh prot | e do
Global values:
  Internet Protocol routing is enabled
FastEthernet0/0 is up, line protocol is up
  Internet address is
Loopback0 is up, line protocol is up
  Internet address is

Now lets configure Router R1 with BGP peer (As we know peer address but not AS number) with Dummy AS number. Here is the quick config:

R1(config)#do sh run | s r b
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 neighbor remote-as 1
 no auto-summary

As soon we configure BGP peer with dummy AS number 1 the following message appears on console:

*Mar  1 00:09:31.019: %BGP-3-NOTIFICATION: sent to neighbor 2/2 (peer in w
rong AS) 2 bytes 00C8 FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF 002D 0104 00C8 00B4 161
6 1616 1002 0601 0400 0100 0102 0280 0002 0202 00
Here is the clue now; Look at this error message and pick the first block of Hex Characters which is 00C8. Now convert this back to Decimal using Windows Calculator(In case you are little lazy like me :-) and you will find decimal number as 200.

Now lets see if we configure BGP peer AS number as 200 and see if it works:

R1(config-router)#no neighbor remote-as 1
R1(config-router)#neighbor remote-as 200

and soon you will see something like this:

*Mar  1 00:13:03.411: %BGP-5-ADJCHANGE: neighbor Up

So magical peering comes up. But lets verify if we have received some prefix from BGP peer.

R1(config-router)#do sh ip ro b is subnetted, 1 subnets
B [20/0] via, 00:00:33

and sure enough we do :-)

Deepak Arora