IP Prefix-List

IP Prefix-list was always whirlwind to me. Every time I was stuck up with ge (greater than equal) or le (less than equal) keywords. So I finally made a mind to write up a strong posting on it, so that one can understand the concept from root and able to implement in network with full understanding. In posted tutorial I tried to explain the basic functionality of ip prefix-list, sequence numbers along with optional parameters ge and le.
Click here to read the full tutorial of IP Prefix-list.

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Innovations can never be stopped

Innovations can never be stopped. I would like to share link of amazing clock which was being share by one of my friend.

The lines of the clock is given below:-

1st Line is Second's
2nd Line is Minute's
3rd Line is Hour's
4th Line is the Day of the week
5th Line is today's Date
6th Line is the Month
7th Line is Year
Click here to see the clock

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Network Outage: %ETHCNTR-3-LOOP_BACK_DETECTED

The network is performing well, unfortunately we received a call that the few of the directly connected to each other are not working and the links attached to the switches were also not working. After logging on to the switches, we saw a weird error message "%ETHCNTR-3-LOOP_BACK_DETECTED: Keepalive packet loop-back detected on FastEthernet0/1". Fa0/1 was uplink to another switch and the port state was showing error disabled. The switch port goes in error disable mode if it detects any error situation on the port. The port is shut down and need to enable manually or automatically if configured. By default, all the cisco switches and routers send loopback frames (ethertype 0x9000) with SA=DA=It’s own mac-address. If the Keepalive packet is received on the same port it was sent from, then a loop exists which even cannot be detected by spanning tree protocol. This is likely the same as of split horizon technique in layer three devices. The problem most likely arises because of unmanaged switches or hubs connected to the switches.
To overcome the problem, we need to add “no keepalive” command under interface which prevents the port from being disabled. This issue is documented in Cisco bug ID CSCea46385.

Disable "no errdisable detect cause loopback" command is another way to handle the problem. By doing this when the switch detects the error disable message of loopback, it will not take any action.

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