Cisco :: 881-W DHCP Conflict With Internal AP?
Jun 13, 2012
DHCP conflict on 881-W with the internal AP?I have (12) 881-W chassis in the field. They are running DHCP services to the wired users as well as to the internal AP for reachability / management / etc. The scope for the internal AP is a /30 so only one address is in the scope and it is intended for the internal AP. This serves a a point to point link between the internal AP and the internal Router inside the 881-W chassis.
Somehow the 881-W DHCP server is getting out of synch and a conflict is occurring. It seems at some point, either at boot-up or lease expiration/renewal, the DHCP server is performing a ping to verify that the address is not in use. The AP has this address assigned prior and replies to the ping causing a conflict. I noticed an AP down today, checked the 881-W uptime and the conflict correlates to the same time. I have to manually clear the conflict and everything works as it should.The existing 12 881-w's could grow to 100's over time, so the manual intervention of clearing the conflict is not going to scale. I really want to stay away from static reservations.
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Mar 15, 2011
I have a Cisco 3750 running DHCP. We have a lot of guest users on the network, so the DHCP conflict table fills up quickly, and when it does, users can not get on the wireless network. I have to go in and clear the DHCP conflict log. (clear ip dhcp conflict *) and the problem is resolved. I see in the Cisco documentation if you don't have a DHCP database agent configured you should disable that log. I just want to make sure what the steps are and the ramifications are of disabling that log. Would IP address's still be freed up to use on the network? It also said about enabling 'ip dhcp ping' so DHCP will ping the address first to see if it's available.
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Apr 21, 2013
We have VSS configured between Cat-6509 switches (s72033-advipservicesk9-mz.151-1.SY.bin)..For the voice vlans,dhcp scope is configured within VSS and ip addresses are assigned to ip phones from these pools configured within VSS.Cat 3750 stack is connected with dual links to this vss. IP phones are connected to cat 3750 switches and desktop is connected back to IP phone. For data vlans IP addresses are assigned from external dhcp server.
Currently we are facing lot of ip conflicts for ip phones and after clearing the dhcp conflicts, IP phones starting getting IP addresses..(sufficient IP's do available in the dhcp scope for IP address assignment). (What exactly the role of no ip dhcp conflict logging command......)
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Oct 8, 2012
Im setting up SBS 2011 in a new office. From what I understand, SBS 2011 needs to be the network DHCP server for everything to run well under Active Directory. The conflict is with a FIOS router, that also �needs� to be the DHCP server in order to communicate with a set-top box (MOCA bridge.) Verizon lists a handful of network configurations with multiple routers that might work, although completely unsupported. Is it possible for router, SBS2011, and set-top box to coexist in harmony on the same network (preferably keeping DHCP server on the SBS box)?
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May 10, 2013
I configured an DHCP server on cisco 3750 switch . Wher in w3750 gets connected to plain l2 switch 2960 on floor and machine gets connected to 2960 port. [code] Below is the description of problem:
-> The Cisco 3750 switch is the DHCP server. VLAN 108 is named as internet vlan.
-> Ports in Cisco 2960 switch has been configured with "switchport access vlan 108".
-> There were no problems at all and everything had been working smoothly.
-> 3 days back, users started complaining that they couldn't access the internet. Up on troubleshooting the issue, I found out that there was an issue with the DHCP server as the computer couldn't get any IP address at all. After setting static IP address, the internet started working again.
If I bind IP to MAc address reservation on core 3750 switch for some time of moment it works but after that machine gets unreachable .I restarted the 3750 switch and also all the 2960 switches over the weekend, however, the issue still hasn't been resolved yet. I did issue the command "clear ip dhcp conflict *", clear ip dhcp binding * but no joy at all.
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Aug 22, 2011
The two controllers are having two internal DHCP servers with the same range in LAN (enx1,enx2). but i have specified which is primary DHCP server(enx3) in WLAN interface.
Now if a new user added into network, will he get IP address from primary dhcp(WLC) or AP connected WLC.
if two users connected to 2 diff AP's which are connected to 2 WLC will get the same IP address? since having same address pool configured.
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Nov 25, 2012
I am wondering if the folowing is a valid configuration:
WLC2504
AP2600
I need 3 SSID/VLAN, 1 for corporate devices, 1 for coporate smartphones, 1 for guest.
Port 1 on the 2504 should be used for management and corporate devices and connect to the corp network. Port 2 is for smartphones/guest and will be connected to a Cisco ASA 5515 that is connected to a second ISP.
Corp devices should get IP from an Windows DHCP. Smartphones/guest should get IP from the WLC. Is this possilbe? I read this in a document "To use the WLC as a dhcp, you need to enable DHCP proxy as it is required." Some how I am imagining that this will mess with the Windows DHCP. Is it better to use the ASA as DHCP for smartphones/guest?
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Oct 19, 2011
I've a question about VPN IPSEC on ASA5510
In the LAN network , we use a DHCP on a Windows2003Server. Is it Possible to Configure the remote VPN Clients to use this DCHPserver throughout the VPN IPSEC and Assigned Automatically IP when the connection is done?
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May 6, 2012
How do Mobility Groups work with internal DHCP scopes on a WLC 5508?We have a WLC 5508 with two internal DHCP scopes which redirect to captive portals for authentication. I am looking at putting in a second WLC in a mobility group setup to provide some WLC redundancy. The LWAPs will be setup so that every second AP is on the has the second WLC as its primary controller. If the primary WLC fails we want the secondary to be able to take over and issue IP's from the internal scope. How do you set this up with a Mobility group so the second WLC does not act as a rouge DHCP server while the primary WLC is still active?
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Jun 28, 2012
We created the management interface, an internal DHCP scope in same subnet, and Two SSID tied to the same management interface:
- when we connect to the first SSID we have and IP address
- but when we connect to the secone SSID: impossible to get an ip address - auth and association are OK
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May 7, 2012
I am hoping to get your feedback around the dhcp issues I am facing with Two Centrally Switched Wireless LANs. The setup is as follows:
- I have a WLC 5508 which has been configured with 4 SSIDs, out of which 2 are using Central Authentication and Switching. - I have an LWAP connected to the WLC in HREAP mode. - WLC is configured as the DHCP server for clients connecting to the SSID 'Guest'. For the rest, I am using external dhcp server. - Only one scope for Guest Interface is setup on the WLC.
Problems:
1. As far as I know, for WLC to act as internal dhcp server, it is mandatory to have the proxy enabled, but the Clients connecting to SSID 'Internet' are unable to get an ip address from the external dhcp server, if dhcp proxy is enabled on the WLC. If i disable the proxy, it all works fine.
2. DHCP does not release the ip addresses assigned to clients even after they are logged out.
3. If a machine which was earlier connected to 'Guest' SSID connects to the 'Internet' SSID, it requests the same ip it was assigned by the WLC which it was assigned under 'Guest', but gets tagged with the V LAN configured on the management interface.
************Output from the Controller********************
(Cisco Controller) >show sysinfo
Manufacturer's Name............. Cisco Systems Inc.Product Name................ Cisco Controller Product Version................. 7.0.116.0Bootloader Version................ 1.0.1Field Recovery Image Version..................... 6.0.182.0Firmware Version..... FPGA 1.3, Env 1.6, USB console 1.27Build Type.......... DATA + WPS + LDPE
[code]...
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Jul 21, 2012
A client wants us to use the internal DHCP server on a 5508 instead of Windows DHCP. They will have 15 APs initially and upto 25 later. The docs on the 7.2 WLC make it sound like this is discouraged: Internal DHCP Server.
The controllers contain an internal DHCP server. This server is typically used in branch offices that do not already have a DHCP server. The wireless network generally contains 10 access points or fewer, with the access points on the same IP subnet as the controller.
In this case, the APs will not be in the same subnet as the Managment Internet.Is it a mistake to use the internal DHCP with upto 25 APs (3 WLANs)?
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Mar 25, 2013
setup a DHCP server on a WLC 2504. I'll try to resume my configuration:
I have 2 networks: inside users (vlan 1) and external users (vlan)
My controller uses the port 1 to connect to the switch, which has a trunk with WLC.
I have two routers, one using vlan 1 (192.168.3.0/24) and one using vlan 10 (200.X.X.X). All ports to these routers are access ports on their respective vlans.
I have 2 SSID, one for inside, other to outside. Inside is working very well.
To the outside I created a DHCP escope and already set the IP of the management interface 192.168.3.119.
Managemente interface (vlan 1 inside): 192.168.3.119/24
Outside interface (vlan 10): 200.X.X.195 - Default gateway 200.X.X.X.193
I alredy checked the DHCP Proxy in Advanced option.
See the output of the debug client:
(Cisco Controller) >
(Cisco Controller) >
(Cisco Controller) >
[Code].....
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Apr 8, 2008
I am trying to setup a guest vlan. I set up an interface for the guest vlan on my 4402 controller. I assigned the guest vlan interface an IP of 192.168.2.10 with a 24 bit subnet mask.
This vlan will go to my DMZ where there is no DHCP server so I need to setup the internal DHCP server. I created a new scope but I'm having trouble with what to put in the Network field for the DHCP scope. The pool addresses are 192.168.2.100-200. with a 24 bit subnet mask.
Every time I try to apply the configuration I get an "error in setting DHCP scope network and netmask".
I've tried using:
192.168.2.10
192.168.2.255
192.168.2.254
as entries for the Network setting but no go. The docs say to enter the IP address used by the management interface with subnet mask applied.
I was assuming they meant the interface for the guest vlan.
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Jan 12, 2012
How to clear dhcp lease in WLC 6.0.199 from the IP leased from internal server?
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Apr 5, 2012
I've got a new CT2504 controller with software version 7.0.220.0 Regarding to [URL]I've tried to configure the internal DHCP on a dynamic-interface, but this is not possible:(Cisco Controller) >config interface dhcp dynamic-interface vlan401 primary 172.16.x.3 vlan401 Interface IP can not be used as internal DHCP server IP It works, if I use another IP (aka DHCP server) in the same subnet or in another subnet. It works also for the management interface.
(Cisco Controller) >show interface detailed management
Interface Name................................... management
MAC Address...................................... d0:c2:82:xx:xx:xx
IP Address....................................... 10.2.x.135
IP Netmask....................................... 255.255.255.240
IP Gateway....................................... 10.2.x.129
[code].....
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Feb 24, 2013
I have a cisco wlan controller (2100) running software 7.0.235.0. I have the internal private wlan running off of port 1 and that is working fine with an internal dhcp server.Is it possible to setup another ssid (guest) and have the interface directly linked to a static ip on the WAN and also use the built in cisco internal dhcp server?
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Jan 19, 2013
I'm using a 2601X router connecting to a broadband connections. The following NAT connections is working but I need to do NAT exemptions to set up my VPN appliance on the DMZ. I see a lot of documentation on how to use a pool of public addresses to do that, but I only have the one dhcp address from my isp.
!
boot system flash:c2600-adventerprisek9-mz.124-25d.bin
!
!
!
interface FastEthernet0/0
[code]....
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Apr 7, 2013
DHCP scope is configured on a WLC 5508.I'm checking if there' a way for WLC to clear the dhcp leasing when a user is diconnected from wireless?
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Jul 28, 2011
In application udp port listening with 3330 i am sending udp request from port 0.0.0.0:3330 to 0.0.0.0:3330 that is same port in the same machine, application works fine with udp sending and receiving also fine, for clarification. s there any conflicts in the communication ?
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Apr 22, 2011
When I sign on the internet, I get a Windows System Error - "There is an IP address conflict with another system on the network." I went to command prompt and typed "ipconfig /renew" but the response was "No operation can be performed on Local Area Connection while it has media disconnected".
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Apr 16, 2011
A couple of days ago my internet was working fine at a speed of around 5mps, I then received a message informing me of an ip conflict, since then my internet has really slowed down to 0.12mbs.
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Jan 4, 2012
Problem with a conflicting IP address. Basically on a normal running day my wireless is switched on and connected perfect to my internet, however if i want to download any large files i plug my Ethernet to my laptop and disable the wireless from my laptop, instantly then the LAN connection kicks in and im on the internet again as i find download speeds are faster through a LAN. However today my wireless is fine but the second i switch to LAN the ! symbol appears and a message says their is an IP conflict.
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Jan 22, 2012
i cant connect to the internet every time i open my laptop. so i have to disable the connection first and then diagnose it to connect to the internet. Pop ups about IP conflict sometimes occur.. what should i do? i already tried ip/release and ip/renew but it didn't work..
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Jan 29, 2013
I've got a wireless network, consisting of two Windows 7 PCs, a wireless printer, an Android tablet and an iPhone. The PCs are always on the network; the other devices only connect occasionally. The router is a Dynamode R-ADSL-C4-W-G1. IP addresses are assigned by DHCP, and both PCs are set up to get an IP address automatically.Now and again, I get an error message on my PC, saying Windows has detected an IP address conflict on the network. I looked in the System Event Log, and found the following message: Quote:The system detected an address conflict for IP address 10.0.0.3 with the system having network hardware address [hex number here]. Network operations on this system may be disrupted as a result.
When I checked in the router settings, I found 10.0.0.3 had been assigned to the other PC, which also has the hardware address given in the error message - I'm not sure how that constitutes a conflict!When I get this error message, I never encounter any connectivity problems - i.e. both machines can still access the internet.
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Jan 12, 2012
I have a Cisco ASA5505 running 8.2(1) and I am using ASDM to manage the firewall. I have a Linux VPN server on the inside with and IP address of YYY.YYY.YYY.39 with a static NAT to the outside with an address of XXX.XXX.XXX.171 . I have a site to site VPN tunnel which terminates on the outside of the ASA on the outside interface XXX.XXX.XXX.190 .Traffic from the YYY.YYY.YYY.0/24 network can't transverse the site to site VPN as there is a conflict of IP address's on the far side so it is natted via a dynamic policy to host address ZZZ.ZZZ.ZZZ.100, Users remote into the inside(YYY.YYY.YYY.0/24) for support via the Linux VPN server (.39) and then need to communicate down the site to site VPN. The problem is that the static NAT for the incomming connections takes preference and bypasses the site to site VPN tunnel for outbound traffic. I tried to create a policy Static nat but it tries to modify the static nat that handels the incomming traffic to the Linux server.
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Jun 26, 2012
I recently changed my home configuration. I have AT&T DSL and I replaced my 2WIRE gateway with an AT&T provided Motorola Modem and a Linksys E2500 router on Sunday. For the last few days, all has been good. Last night and this morning, one of the computers in the house began getting IP conflict messages. The computer is provided by my company and uses the Cisco VPN client. I am not sure if it is conflicting because of the VPN (only seems to happen when it's connected) or with one of the other devices on the network (i have four other computers, a game system, and a few phones on the network).
Is there a way to prevent a conflict from happening again? My work requires me to have a constant connection for days at a time and these IP conflicts are causing constant headaches. Would creating a static IP address on the work computer outside of the DHCP range clear this up?
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Aug 5, 2011
I'm trying to perform ping to another network segment using nat to those devices but the ipaddress i assigned are the same as the segment i am trying to monitor is there anyway to overcome this?
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Jul 25, 2012
Can an IP conflict cause network issues for computers other than the devices that have the same IP? I have resolved an issue where someone was testing a device on our network and assigned a static IP that was already in use by one of our printers. Specifically, I am curious if the IP conflict could have caused issues with mapped network drives for other computers. I just seemed to have network gremlins for the 2 days of the IP conflict.
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Oct 26, 2012
I've been getting a popup error message for about a week:"There is an ip address conflict with aother system on the network". This is only for 2 desktop PCs with wired ethernet connections. Wireless devices are fine with no error message. The wired LAN PCs basically lose all network capability. Reboot fixed it, but it returned every time it was rebooted.I have a Virgin Media Superhub with another router configured as an access point. To cut a long story short, after trying to reset everything, re-installing network adapters & swapping ports, I decided to set the Superhub to Modem Mode, and re-configure the access point router to act as a standard wireless router. In other words renewing the whole network's LAN IP addresses.I now don't lose network capability, but the error message is still appearing on both wired LAN PCs. I use the Fing app on my android phone which lists IP addresses for all devices on the network, wired and wifi, and no 2 addresses are the same, which suggests that DNS is doing its job.
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Mar 20, 2011
I have been having router/wireless internet issues since my internet provider had to come out and fix the outside lines. Ever since then I get the Network Error: "Windows has detected and IP address conflict" whenever my laptop and my wife's try to use the wireless at the same time. I have tried release/renew of my IP address and also reseting my router to factory settings to no avail.
Computer info and ipconfig/all:
Tech Support Guy System Info Utility version 1.0.0.1
OS Version: Microsoft Windows 7 Home Premium , 64 bit
[Code].....
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Jul 10, 2012
[code] Whenever I am browsing online, every once in a while the internet just cuts out. It still says I am connected to my wifi network, but there is "limited or no connectivity." Whenever it happens, everything on the network loses its internet at the same time. In the household, there is one PC (mine), one Mac (my wife's), one iPod touch, and 2 iPhones that all connect to the wifi. The vast majority of the time, when this problem occurs, simply unplugging the router and then plugging it back in fixes the issue.Sometimes however things are different. Especially lately, I sometimes get an "IP conflict" error message. It says another device on the network is using the same IP address. Sometimes with this error simply unplugging and replugging in the router works. Sometimes the router has to be reset twice before things start working again with this error. The error doesn't happen every time the disconnect occurs, but it seems to be getting more frequent lately.Sometimes the disconnect happens when I am playing an online game that requires a constant connection to the internet. Sometimes this goes as usual, where a single router reset fixes the problem. However, sometimes this situation gets more complicated. One game in particular (League of Legends, if it matters) has this problem all of the time. When the internet disconnects while this game is playing, I do not get the "limited or no internet" warning. Instead, the computer seems to think that it is connected, and that the internet is working.
During this scenario, resetting the router once is never enough. After resetting once, the wifi reconnects and now it realizes something is wrong. After the first reset, the computer seems to "realize" something is wrong after all, and I am connected to the network but this time with the "limited or no internet" warning. A second router reset after this usually fixes the problem.Last night the worst disconnect happened yet. It was in the middle of a game, and the internet cut out, with no warning on the network. After one router reset, the wifi network reconnected immediately with an "IP address conflict" error, and then I was connected with "limited or no internet" on the network. I did the second router reset as usually required, but nothing happened. After a second and a third reset, there was still a permanent "limited or no internet" warning.I tried hardlining in directly to the modem and there was still no internet. Running the network diagnostic on my laptop fixed it however and I was connected to the internet. However, wifi still would not work, even after trying the diagnostic again. Running the diagnostic came up with an error that the DNS server was not responding and so nothing could be done.This time I reset everything. Unplugged both the router and the modem and left them unplugged for 30 minutes. When I turned everything else on again, same issue. Connected to the wifi network, but "limited or no internet." I unplugged everything again, left them overnight, and this morning after plugging everything back in the internet was back.A few final points I think might be relevant:
1) When checking the system event logs, it's usually a DNS error that I get (see event logs, 1st attachment).
2) This disconnect error seems to be more prevalent when more devices are on the network. As I said, they have gotten more frequent lately, especially the IP conflict warnings, since the 2 iPhones were added a few weeks ago. 5 months ago when it was only my PC on the network, these issues were practically non-existent.
3) It's a Belkin wireless g-plus router. Model # F5D7231-4 version 1213. It is an older router.
4) This has been happening for almost a year, but just recently gotten so bad I have to get this fixed, especially after last nights that could not be reset no matter what.
5) I'm not sure the disconnects have ever happened why the PC is not connected. That may not be relevant however, because my PC is almost always on since I work from home, while the iPhones, iPod touch, and my wife's Mac are only connected periodically.
6) This error has occurred while my PC is the only device connected to the wifi network, but it seems much less frequent.
7) The time the error seems most likely to occur is when another device connects to the network, such as when my wife first gets home from work. This is not exclusive however, and the DC's can happen at any time.
I've seen that people want ping tests and ipconfig /all tests so I will post mine. I will edit my post with the same tests done the next time this dc happens. I've also included a screenshot of that xirrus wifi program. [code]
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Oct 19, 2012
There are about 3 laptops, one desktop, and 2 gaming consoles that are using the router. Everything connects fine expect the one laptop. It is an ASUS laptop running Windows 7. Whenever the laptop is going to connect to the internet every other device using the internet is stalled for a few moments, then reconnects. The computers then give the IP Address Conflict message. This is extremely frustrating. Sometimes it happens when people are accessing the Web for college assignments, and sometimes gaming, which is annoying to get disconnected from. I have tried to release / renew the IP, but it tells me it can't complete the process.
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