darinjw
asked on
Network Engineering Dilemma - Thoughts appreciated
I'm researching a particular scenario and the feedback here is always great. I've hit a bit of a bump on this particular scenario and would love to get feedback from resident experts. The scenario is as follows:
There are 8 branches and random users at a single branch are unable to access internal applications or the Internet.
All other branches are working as expected and the majority of the users at the effected branch are working as expected.
· Each Branch is connected with a 10MB connection to the Internet
· Each Branch is using a /24 subnet
· Each Branch is using DHCP
· Each Branch has 90 employees (Laptop, Phone, Tablet)
What could be the problem? What steps do you take to identify the issue? How would you solve it short term?
My initial thought here is that the DHCP pool is exhausted, however, what little I know about subnetting indicates that only 254 hosts could join the network, but every other branch is comfortably supporting 270. Any thoughts on how to answer the three questions would be great.
There are 8 branches and random users at a single branch are unable to access internal applications or the Internet.
All other branches are working as expected and the majority of the users at the effected branch are working as expected.
· Each Branch is connected with a 10MB connection to the Internet
· Each Branch is using a /24 subnet
· Each Branch is using DHCP
· Each Branch has 90 employees (Laptop, Phone, Tablet)
What could be the problem? What steps do you take to identify the issue? How would you solve it short term?
My initial thought here is that the DHCP pool is exhausted, however, what little I know about subnetting indicates that only 254 hosts could join the network, but every other branch is comfortably supporting 270. Any thoughts on how to answer the three questions would be great.
It can be switch problem or some network problem, may be loop. How often it happen, do you have this problem every day? You have to take all possible problems and narrow it down. It can be something with wifi access point. You may have saturation max out, cpu max sometimes.
Can you tell us a little more about this network? What switches, what access points you have, how many clients on wifi and how many on cables?
Can you tell us a little more about this network? What switches, what access points you have, how many clients on wifi and how many on cables?
As you mention, and others have referenced, it is impossible to have more than 254 simultaneous hosts in a given /24 network, at a time. Which means that DHCP lease times must be pretty short, because some, inactive devices, are going to have to give up their leases fairly frequently so that others can take them. So this may very well be a DHCP issue. As others have mentioned, it could also be something else - like a switch port - that's causing the problem for this particular device. I would definitely recommend taking Olgierd's suggestions. And if they don't work, you might want to consider widening the network scope for that branch office. It seems that, in any case, you're running pretty tight on addresses there. Can you give it a /23 mask, for that office? If it's too close to others, can you change the range entirely, and THEN give it a /23 mask?
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A few questions for you:
1) did you check your DHCP server to verify if all of your IP addresses are binded? If so, verify that your lease time is not too long (4 hrs vs many days)
2) for the users unable to connect, have you verified their IP address?
3) Also ping your default gateway from that workstation (ping doesn't always answer back, so verify if there is an ARP entry by typing arp -a in a command line)
4) Also, I would do an ipconfig /all and check that the DHCP server listed really is your server (sometimes users run out of ports and buy a linksys or something else like that... and DHCP is enabled)
If this doesn't put you on the right track, please let me know what you found out with the above suggestions.
Good Luck!