• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 144
  • Last Modified:

Laptops acquire wrong DCHP, DNS and Gateway address for Wireless

Our company is on a 192.168.14.x private network. Our DNS/DHCP server is at 192.168.14.5 and the default gateway is at 192.168.14.1 In the past week, random computers on our network have been getting the incorrect DNS server of 192.168.14.235. This address is the Cisco phone system.

When a computer has the incorrect DNS server, they have no connectivity to the Internet. We tried resolving the problem by running ipconfig /release and /renew, and ipconfig /flushdns; we also tried a winsock reset, None of these things resolved the issue.  We tried assigning a static address, which worked, but when we removed the static if failed back to the 14.235 phone system address again.

The computer is running Win10 Pro X64. The weird part of this is that the PHone system does not have any wireless conbnection and the problem oly affects the wireless; the wired connection works properly

Incidentially, there have been no configuration changes to any networking equipment or to the phone system this year and this problem 'suddenly' popped up last week.

Does anyone have any idea why this is happening and how to resolve it?
0
LostInWindows
Asked:
LostInWindows
  • 4
  • 4
  • 3
  • +2
2 Solutions
 
JohnBusiness Consultant (Owner)Commented:
Take one problem laptop and try the following:

Open cmd.exe with Run as Administrator
Then  netsh int ip reset c:\resetlog.txt
Also, ipconfig /flushdns followed by net stop dnscache followed by net start dnscache
Then restart the computer

Does this solve the issue?  If so, TCP/IP Reset and DNS Flush is very easy to do on the others.
0
 
max_the_kingCommented:
Hi,
chances are that computers are connected on the phone which is connected to the switch, and they get the dhcp parameters which should be peculiar to phones.
If this is the case, the main anomaly is that you have both PCs and phones on the same vlan, which should be avoided. If you cannot implement vlans to separate traffic, you can either disable dhcp server on cisco phone system (and give phones static IPs) or fix the 2 DHCP servers in a way that they do not mess each other.
In you actual situation, if i understand well, PC and phones get their IP from either a dhcp server for PC or the Cisco phone system: you might as well have a unique dhcp server giving the same DNS parameter. It will be just a workaround, due to the fact that phones and PCs should be on different subnet.

hope this helps
max
0
 
Istvan KalmarHead of IT Security Division Commented:
Hi,

It seems, that you not configured vlan for PHONES, or you not configured properly the switches, if you use cisco swithes you need

Switch#conf t

Switch(config)#interface GigabitEthernet <interface ID>

Switch(config-if)#switchport trunk encapsulation dot1q

Switch(config-if)#switchport mode access

Switch(config-if)#switchport voice vlan <Voice VLAN ID>

Switch(config-if)#switchport access vlan <VLAN ID>
0
Become an IT Security Management Expert

In today’s fast-paced, digitally transformed world of business, the need to protect network data and ensure cloud privacy has never been greater. With a B.S. in Network Operations and Security, you can get the credentials it takes to become an IT security management expert.

 
LostInWindowsAuthor Commented:
I appreciate all the comments. Here is some more infor:
  • The phone system has been installed for about 3 years.
  • All the phones have their own wiring back to the phone system.
  • We do not have a managed switch on site.
  • The laptop connections worked perfectly until a couple of weeks ago when, after no changes, the wireless started getting wrong IP information.
  • Although I may be able to sell the boss on a managed switch, as it did work before for years, I am thinking that the managed switch, although nice to have, isn't required.
  • The Wi-Fi comes from the router and the computers using wired connections do not have an issue.
0
 
masnrockCommented:
Is the firmware up to date on all devices? Have you checked the settings for the WAPs and/or WLAN controller? You also might want to check the switch settings for the ports the WAPs are on.
0
 
max_the_kingCommented:
Hi,

The laptop connections worked perfectly until a couple of weeks ago when, after no changes, the wireless started getting wrong IP information.

it may well be that the dhcp server used so far has run out of IP addresses: you should check there.

max
0
 
LostInWindowsAuthor Commented:
I ahve determined that the IP information that the wireless devices are getting is coming from the Cisco UC500 Phone System. If I can figure out how to disable the wireless, my problem would be solved.
0
 
JohnBusiness Consultant (Owner)Commented:
Log into the Cisco wireless and disable Wi-Fi
0
 
LostInWindowsAuthor Commented:
I will, but I have to determine the CLI to do that. I am not bilingual. I don't speak Cisco.
0
 
JohnBusiness Consultant (Owner)Commented:
Perhaps a Cisco expert will look in here.
1
 
masnrockCommented:
Do you have the Cisco Configuration Assistant? You might be able to work that way to get it disabled.
0
 
masnrockCommented:
Here's a link to download Cisco Configuration Assistant:
https://software.cisco.com/download/release.html?mdfid=281010085&softwareid=281161599&release=3.2(3)&relind=AVAILABLE&rellifecycle=&reltype=latest&i=rm

And here is a link that talks a bit about configuring wireless on a UC500:
https://supportforums.cisco.com/document/34261/wireless-security-cisco-unified-communications-500-series-cisco-smart-business

Basically, this gives the sections you need to go to in order to work on wireless settings, but you will instead be looking to delete or disable the wireless related settings.
0
 
LostInWindowsAuthor Commented:
Thanks to all who submitted comments. Now that we have Wi-Fi disabled on the cisco, everything works as I exect it to.
0
 
JohnBusiness Consultant (Owner)Commented:
Thank you for your update and I was happy to help you resolve your issue.
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Improve Your Query Performance Tuning

In this FREE six-day email course, you'll learn from Janis Griffin, Database Performance Evangelist. She'll teach 12 steps that you can use to optimize your queries as much as possible and see measurable results in your work. Get started today!

  • 4
  • 4
  • 3
  • +2
Tackle projects and never again get stuck behind a technical roadblock.
Join Now