Category Archive: Routing & Switching

Aug 25

Monitoring Cisco Switch Port Discards

If you are using a monitoring software such as Opsview or Orion, you will see sometime that you get a warnings on switch port discards. The first thing to do usually is to  check the actual switch port by using 'show int xx/xx status'. However this command would show rest of the details but nothing about …

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Nov 28

Duplex Mismatch – How varying Duplex/Speed settings can effect connectivity?

Well, let first explain couple of terms when dealing with Duplex and Speed settings on Cisco Switches. These settings determine what will be the status of the link when an end device is connected to switchport. You will have to keep the settings on NIC of end device in sync with switchport config to make …

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Aug 02

Don’t span high volume traffic to WS-X6548-GE-TX or WS-X6148-GE-TX oversubscribed line cards


Don't span high volume traffic to WS-X6548-GE-TX or WS-X6148-GE-TX oversubscribed line cards. I was scratching my head for the last two hours after a span session I created on 6500 caused other network users loose network connectivity/slowness. Later I find out that the line card I used to sniff traffic is not fit for …

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May 24

RSPAN Configuration for Cisco 6500 Switches

Depending on the IOS Version and platform, the Remote SPAN configuration can be a bit different. In this post I will be configuration RSPAN session between a Cisco 6506 switch running IOS Version 12.2(33)SXI and Cisco 6509 running IOS Version 12.2(17d)SXB1.





Source: Cisco 6506 (IOS Version 12.2(33)SXI)

1. Configure …

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Mar 18

Connect GNS3 Network to Real Networks / Other GNS3 Network

This posts details how to connect GNS3 network to real networks. you can use this post for various scenarios, in fact whatever you can think of. So, say for example you have a physical router connected to your home network and you want to configure VPN between your router and  ASA (or any other device) …

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Mar 15

Cisco MDS 9000 Series AAA Configuration

Here is a sample for Cisco MDS 9000 Series AAA Configuration. There are two parts of it, one is to config ACS Server and Second is to configure the Switch itself. First I am detailing the switch configuration and then the ACS Config.


Switch Configuration

We need some basic knowledge of the setup before …

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Mar 15

Cisco MDS 9000 Key Mismatch Error for SAN-OS Version 3.1 – AAA Config

Though 3.1 is quite old version but still maybe in use on Fabric Switches somewhere on your network. While configuring AAA on these switches you specify Shared Secret key which matches with what you had configured on your ACS / Radius Server. The product documentation states that you can any secret key within certain length …

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Mar 13

Telnet to Router Interface from outside


This post answers the typical question of how to Telnet to Router Interface from outside. Also it details the configuration steps which enables telnet access to router’s outside interface.

I have setup a small lab on GNS3 to give an exact idea of how an internet facing router is typically

configured and how you can modify …

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Jan 27

EIGRP Delay Settings

Cisco EIGRP has the default behaviour of equal cost load balancing. It does that after calculation the metric which considers the minimum Bandwidth and total Delay along the path for a destination. Now, if there are equal paths available to a destination network and we don't want EIGRP to do equal cost load balancing we will be targeting …

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Jan 19

Cisco 6500 Ignores NTP Requests

I faced an issue with one of our 6500 series switches where 6500 acting as NTP server was not replying to some NTP client which access the switch on a certain port. The clients accessing the switch on a different port were able to sync OK. The version used on the switch is quite quite old but this …

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