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Posts Tagged ‘GNS3’

Improving the Routing Table in an OSPF Network

posted in Cisco Networking
by on December 1st, 2011 tags: , ,

OSPF Network

The topology above is an example network, consisting of four OSPF areas (one backbone, area 0) and one external EIGRP area. I’ve set up an IP addressing scheme using 10.0.0.0/8 for OSPF and 172.16.0.0/12 for EIGRP. In case you didn’t notice, the second part of the IP address is the same as the area number (10.x.0.0 for area x).

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ICND1 Practice Labs

posted in Education, Training
by on February 2nd, 2011 tags: , , , ,

I’ve created a handful of configuration and troubleshooting labs to help CCENT candidates refine their skills in preparation for exam day. These labs cover a good portion of the core ICND1 IOS fundamentals and require a thorough understanding of the Cisco IOS to complete.  Some labs do present unexpected obstacles not covered within the lab objectives to help demonstrate specific networking theory under normal conditions.

All routers that do not require configuration changes are locked.  Some labs may also only allow for Telnet or SSH connections.  It’s up to you to configure each device as you would remotely in the field or on the exam to complete each of the lab objectives.  These labs can get a little tricky and were designed to give capable ICND1 candidates with reasonable IOS experience a headache, so be patient.  When finished with a lab, you may compare your results with the provided answer sheet.  Have fun!

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Enterprise BGP Lab

posted in Cisco Networking, Technical
by on April 29th, 2010 tags: , , , ,

Today we’ll go over a dual-homed enterprise BGP deployment. We have an enterprise in AS 6500 connected to ISPs in ASes 1111 and 2222, respectively. We also have a router in the cloud simulating the internet (injecting loopbacks) and routers in our DMZ simulating servers, and a loopback on the IBR simulating a LAN. In the post we will only go over configuration for BGP in AS 6500 (otherwise this will be far too long), but I’m including the initial configs for the other devices as well as the final configs for all devices. I’m using 3725s here, but nearly any router in Dynamips should be sufficient.

Here’s the topology:

topology

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MPLS VPN Challenge

posted in Cisco Networking, Technical
by on January 23rd, 2010 tags: , , , , , , ,

I spent some time using GNS3 to build out a 3 router lab focusing on a single customer MPLS VPN. Everything went fine initially, OSPF came up, BGP with route reflectors were fine, LDP neighborships established, and I even saw VRF route advertisements across the network. The problem came when I tried to PING across the network on the VRF from one customer subnet to the other, I got nothing. I spent about an hour troubleshooting, looking up examples, and pulling out my imaginary hair before I figured out the problem. In this blog post I will present the lab as it was originally built for the sake of discussion and leave it up to you to figure out where I went wrong and why exactly it wasn’t working.

Here is the networking drawing as built in GNS3:

lab challenge

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