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NetAcad, Exercises, CCNA, CCNP

Keeping PuTTY telnet session alive

Working with my HP Terminal server, which we are using as a remote console acccess solution allows us login into Cisco router console ports remotely, i'm loosing the Putty connection due to inactivity. However the PuTTY client can be configured to maintain a connection and not time it out. All what we need to do is setup built-in keepalive machanism:


1. Open the PuTTy application 

CCNP - Route redistribution - Simulating routing loops


Teaching CCNP ROUTE courses and describing the problematic of two-way routing redistribution I need an example describing the case which point out to the process of creating a routing loop. This example shows how such routing loop may arise using badly configured redistribution process andusing bad seed metric. The topology with two redisitributing routers creates routing feedback (two way, multipoint redistribution). The loop is created for packets routed from the ospf network to the destination network.

Display CCNA curriculums locally

Once if we are allowed download zipped version of ccna curriculum (for example as an netacad instructor) we should be able run them locally without web server need. However there is a problem to display these curriculums by default as it contain embeded flash animation. This problem persists in different browsers (firefox, chrome, epiphany) for example.

Enabling default Telnet client on Windows 7 operating system

In our Cisco NetAcad classes we had utilized built in Windows telnet client (of course we have putty instead), which was available in each system till Windows XP by default. In windows 7 the telnet client is not available by default, but we simply may do it available in few simple following steps:


1) Open Control Panel and choose Programs and Features

2) From the left meny choose "Turn windows features on or off"


STP - Loop itself with BPDUfilter

We investigate a special topology condition, where a switch is connected itself on ports Faa0/1 and Fa0/2, and one of the port has BPDUFilter feature applied (i.e. simulating STP is switched off). Both ports are in the same vlan (vlan 1 here). The question is: Is there a topology loop?

Initial state

We check first interfaces status, where we should see that both ports are connected and operational

Router IP Traffic Export - the router packet capture capabilities


Cisco switches provides SPAN and RSPAN feature which is suitable for monitoring and capturing packets flowing through switch ports or VLANs. But this feature is not provided on Cisco routers, therefore if you look for it there is not result.

VTP (+DTP) security threat - myth or fact?

There is some confusion and misunderstanding regarding VTP (VLAN Trunking Protocol)+DTP (Dynamic Trunking Protocol) and this article will hopefully make it all clear. Most of the confusion comes from the statement that VTP is always a security threat to your network. There are even some CCIE material which I find to be wrong on this topic so my advice here is to test everything by yourself.


I assume that you have sufficient knowledge about VTP and DTP, if not or you would like to refresh your memory take a look here:



List of supplementary learning sources usable for "642-902 ROUTE - Implementing Cisco IP Routing" certification

This is a list of supplementary study materials usable for learning CCNP 642-902 - Route course and supporting following successful certification. They allow a deeper knowledge and support better orientation on selected topics. The contain links on externel Internet sources how I recommend it to my students during my CCNP lessons ofn our Cisco networking academy.

Main resources, of course, are following books:

Loki - L3 packet generation and manipulation tool

Notes: Loki is a Python based framework implementing many packet generation and attack modules for Layer 3 protocols, including BGP, LDP, OSPF, VRRP and quite a few others.


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