but it's all part of job and entertainment. So few minutes later I logged into the network using my VPN access to see what's going on. So as I logged in into the network, I found ..... "Nothing". I mean everything was looking ok and there wasn't any log into the ACS (Used For AAA based Access) suggesting someone made changes into the network on Friday. Also no log into local log of concerned devices stating any reason.
So after this initial investigation I was pretty sure now that there wasn't any change made in the network since Friday. Which leads to conclusion that it's either problem with the Unix server itself or there is some configuration issues with the server.
Next I dropped any email back to unix guy stating I didn't find anything unusual, please confirm if:
> Any changes were made into the configuration of Unix Server recently ?
> Restart the network Services of the Unix Server
> Send me "ifconfig -a" command output from Unix Server command prompt.
BTW... "ifconfig -a" is equivalent to "sh protocols" in Cisco IOS world and "ipconfig /all" from Windows OS world.
and just a minute later the Unix guy replied me back stating:
> There were no changes made into the configuration since last few days
> Restarting network services didn't help
> ifconfig -a results attached
# ifconfig -a
inet 127.0.0.1 netmask ff000000
inet 10.136.110.149 netmask ff000000 broadcast 10.255.255.255
inet 172.17.1.132 netmask ffff0000 broadcast 172.17.255.255
So as you guys can see, the E0 Ethernet interface is Running fine and even IP was looking good from my prospective since I already had checked the VLAN subnet for it. But did you see the mask highlighted with YELLOW color ? Isn't that looking weird ? I mean did you ever know that there are some devices out there which takes netmask/subnet mask into Hexadecimal format ?
At-least I didn't....
So next step was to determine the subnet mask into Decimal format to see if it matches my network device configuration. So I quickly took the windows calculator and tried to conver ff000000 into binary. Though It took a min or two to figure out how many digits from Hex needs to be picked up for each decimal block. And the answer was "Two"
so finally I had answer that subnet mask was put by unix administrator was "255.0.0.0" where my vlan subnet configuration was configured for different subnet mask. So I quickly replied unix administrator suggesting to change the subnet mask to the correct one and of course that fixed the issue.
After that next morning I did some research on Subnet mask in Hex format and found that some old Unix box use to support it in that format only.
But one interesting thing I found was that our very own Cisco IOS also supports that format. And I was like :
Yes. So I quickly did some test and here are results:
R1#sh run | i terminal
R1#sh run | b netmask
ip netmask-format hexadecimal
line aux 0
line vty 0 4