Hey we have another contributed lab. This one comes from Brahadesh.. He put together a little lab based on a exercise from another site and contributed it here to us.

It’s great that you can find an exercise on the internet, whip it up real quick, work on it and share it afterward. It’s amazing how Dynamips/GNS3 allow such capability to lab and work out real world scenarios with little to no effortt.

Thanks for the share Brahadesh! Hope to see more..

Now onto the lab!

-Lenny

Scenario

Here is a little scenario which i came across on this website. Please go through the site to get a better understanding of the Goal of the lab.

http://nil.com/ipcorner/SmallSiteMultiHoming/

However let me give a Brief about the goal of this lab

Remote site has two ISP’s that allow only static routes into them and no routing protocols. Remote site needs to be Connected to the Central site all the time, However Remote site prefers to connect to the central site Via ISP A ( in this case Via R0-R1-R3).But remote site should start using the second path i.e R0-R2-R3 if the main link fails.

Goals

We are using the IP SLA concept to create a tracking object, To Track the IP address 3.3.3.3 ( This can be a server at the central site). Remote site uses Two Public IP addresses provided to it by the Two ISPs. Routers R1 and R2 are the ISPs and R3 is the Central office router. Use natting to translate Private IP space within your network to the Public. For simplicity I use OSPF between R1, R2 and R3 to exchange routes.

1) Configure R0,R1,R2,R3 IP address and Loopbacks

2) Configure OSPF on R1,R2 and R3 make sure the routes are exchanged

3) Configure NATing on R0, You have make use of Route maps to create NAT pools on per interface basis.

4) Configure IP SLA to poll your Central Site( 3.3.3.3) at a set interval of every 3 seconds, and start the polling NOW.

5) Create a track object to track the IP SLA polls

6)Finally create  a delay of  10 seconds when the route goes down and 20 seconds when the link recovers.

7) Create 2 static routes pointing to each ISP, Force the  router to prefer ISP A by influencing the metric.

Attach the static default routes to the Track object to remove them from the routing table if the primary link goes down.

Above are just guidelines, detailed configuration steps can be found on the link given above, or in the attached configs.

Note: I turn off Keep-Alives on the ethernet interface of the Router R0, to fool the router to think it is actually Up. Helps you keep the topology simple.

Forgive me if the IP addressing scheme seems foolish. I created this lab on the fly did not think much about the Ip addressing.

Routers Used: 7200

IOS: c7200-adventerprisek9-mz.124-4.T1.bin (This lab needs IOS version 12.4 or later)

Feature of Topology: IP SLA, Object Tracking, NAT, Route Maps, OSPF

Image:

Download: GNS3-Labs-Small Site Multihoming-Brahadesh

Regards,
Brahadesh

Tags: 7200, GNS3 Lab and Exercise, GNS3 Topology, IP SLA, NAT, Object Tracking, OSPF, Route Maps