این پیغام زمانی نشون داده میشه که یک MAC آدرس از دو پورت وارد سوییچ بشه.
So, I was doing some practicals today in the Cisco labs at QUT and I came across something I found awfully hard to troubleshoot! I found, that while I was trying to set up port security on some FastEthernet connections that were connecting to hosts, the switch was telling that there were two MAC addresses coming from my host. I was utterly confused! I thought it was something to do with the switch, or maybe my running-config so I spent ages looking them over and checking to see what the issue was. I was using two computers to simulate two hosts apart of the same VLAN across a few switches as seen below.
I had set my ports to only accept one sticky MAC address, because they would only need one as they were connected to a host and that is what the practical was telling me to do. But, for some strange unknown reason, the ports would shutdown because almost instantly after coming online, they received two different MAC addresses. I had to change the maximum number of MAC addresses to 2 using switchport port-security maximum 2 on the Interface. Take a look below, at what I saw when the two MACS cohabited
peacefully.
This strange MAC address, that clearly didn’t fit – 0201.0000.0000 was somehow, coming in off my FastEthernet port and I had no idea why or how or why! especially, when I didn’t have this issue on one of my other switches that my other host connected to it making up the network simulation. I looked at my running-config on both switches over and over and was completely lost!
It wasn’t until I decided to connect my computer back up to the university network, to get Internet access, so I could Google this address that I found the problem. And the problem as it seems lies in the operating system Windows Server 2003 that I was using on my hosts. Turns out, there is a function in the LAN adapter on Windows Server 2003 that is installed that faciliates and enables Network Load Balancing. Now, this funny address, was apart of that service on my computer. And the reason I didn’t have the issue on my other host was because the service was disabled. On the offending computer as shown below, you can see the network service enabled.
So, all you have to do to get rid of this pesky MAC address that keeps appearing across your MAC tables and whatnot, is disable this service like shown below.
And, with a simply unchecking of the box. You are free of this problem! and with that, I was able to change my port security maximum back to 1 MAC address and have the sticky MAC learning work as it should. So! what did I learn today? when setting up the IP addresses at the beginning of your simulation, make sure to have Network Load Balancing unticked if I’m working on Windows Servers 2003 or 2000.
0201.0000.0000 Problem Solved! | Technology | Mitchell Pearson
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