The Dynamic Host Configuration Protocol (DHCP) is an auto configuration protocol used on IP networks and an extension of the Bootstrap Protocol. DHCP allows for computers to be configured automatically to communicate with each other over an IP network without the need for manual setup by a network administrator. The implementation of DHCP relies on a DHCP server to hand out network configuration information to DHCP-capable clients that request an IP address (and other information required or useful in communicating with other devices on an IP network). In addition to an IP address, common configuration information served over DHCP includes a default gateway, subnet mask and DNS sever(s).

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Hi All,

i am trying to get a 2012 server to use two ranges of IP's in the same DHCP scope, i have changed the Subnet Mask to and the two ranges i'm tryign to use is -  it worked fine and handed out 192.168.1.xxx addresses, but i wanted to test it as if all the 192.168.1.xxx addresses were used up, so i excluded them out of the range but then  when i plug my laptop onto the network of the server it doesn't give me an IP address.  i would have thought it would just give me an IP of 192.168.0.xxx.  but it hasn't and if it has then the default gateway is blank.

any suggestions?
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I had a requirement which I like to check if its possible to assign an endpoint ip address by the radius attribute Framed-IP-Address for 802.1x client?

An example is an endpoint performed 802.1x and its ip address is assigned by Radius Framed IP Address attribute based on selection such as user name using radius server such as Cisco ISE
We have a problem with our remote clients that are terminating across the cisco anyconnect VPN.  Currently we are unable to browse to the \\unc path of the said remote client, but not all machines.   The problem has been intermittent for a over a year now.  It has gotten worse since 1809 update to Win10.

We can browse from remote client to the LAN and UNC paths.
We can ping both ways i.e. 172 (local LAN) to the remote vpn client IP 10.255.255.*.
DNS is registering the 10.255.255.* IP in reversse lookup.
DNS is also registering local IPs on the forward lookup zone domain.local - this seems to be what is being resolved.

Im thinking its DNS wrongly configured but hesitant to make changes...

Any ideas?

I have (several) 7301 routers running 15.2(4) that are located behind Comcast routers.  I need them to VPN to a public router knowing that the Comcast IPs might change at any time based on factors outside of my control.  So the central VPN point is my only fixed location and the 7301s all sit BEHIND a vendor provided router.  The 7301 gets its IPv4 from a DHCP server (again, can change) and its IPv6 from SLAAC.  The central router has both fixed IPv4 and IPv6 addresses on it.

My goal is to route everything on the G0/1 side of the 7301 to the central router (ASR running IOS-XE 3.16.07b [asr1001x-universalk9.03.16.07b.S.155-3.S7b-ext.SPA.bin]) including both IPv4 and IPv6.  I'll want to run OSPFv2 and OSPFv3 across the link.

Note that the central router is actually on the public network with real world IPs.  The 7301 is behind a Comcast business router *somewhere*.  The goal is to create a tunnel for IPv4/IPv6 between the G0/1 side of the 7301 and the central router.

Performance is a plus. Secure tunnel is not a requirement, but nice as long as its not a significant impact to throughput.

My assumption is that the 7301 will have to initiate a connection to the central router. But in all my experimentation, I haven't been able to create a GRE tunnel without a valid destination (which the 7301 does not have) nor have I yet been successful in an IPSEC tunnel that can carry both IPv4 and IPv6 over it.
Fortigate 110C - How do I configure 2 or more Lan interfaces and for each separate DHCP - If I cant have the option to define each port?
What is the VLAN that I can create ?
Im attaching screenshot of the main screen...

I am one of the network admins of a business complex, containing several different companies.
To handle internet for every company, we have an Ubuntu machine acting as a gateway.
There's several static. public ip-adresses, and several dhcp-networks, all being handled by this gateway(it acts as dhcp too)

What I need is something to monitor network traffic flowing through the gateway.   I've tried with NTOP, but I haven't been able to get the data I need, or, atleast, I don't understand how I'm supposed to. i've been looking in a graphical interface for it.

What i would like to be able to see, if possible, is what VLAN or what IP, be it static or set by the dhcp server on the gateway, is accessing what. If it's possible to get the type of traffic on that specific VLAN or IP, and even if there's possible to see what IP-address that specific host has.
It would be great if there's an interface for it accessible through http/s.

I've been looking some at munin, and nagios, but haven't really found out if this can do what I need.

Any tips?
So far the one most seem to suggest when I've googled is Ntop. but I can't seem to get the data broken down into VLAN level or something similar. I might have missed something in the configuration, but...

So if anyone have any tips or good sites with documentation to set up what i need to do, it would be very appreciated.

Thank you

Hi Experts,

We have 25 wireless access points in our LAN, some of them are Netgear Genie, Netgear Nighthawk, Netgear N300, TP Link, D-Link and Unify access points (Mash wireless devices).

we never had any issues with them util last Thursday when all of a sudden users had started complains about loss or wireless connectivity and slowness, we figured out that the DHCP wasn't leasing IP's due to network card failure. We installed new DHCP server and users started receiving IP's, now we have observed that max 15 access points can be up at a time and if we try to add and start using another AP then wireless user started facing extreme slowness or complete dis connectivity as soon as we remove that additional AP then everything get back to normal.  

The strange part is if we use port as a switch for wired connected devices (PC, laptop or a server then it works perfectly fine with any issues but as soon as we start connecting to AP as a wireless user than wireless services starts moving downhill.

The Ethernet connectivity (wired) is fine and not even a Singal issue ever reported, the wired and wireless they both sharing same LAN, we don't have any wireless controller in the network.

Please share you expert opinions and knowledge to mitigate this issue.

Awaiting for your reply.

Thanks in advance.


Abdullah Jamali
I have 2 AD-Integrated DNS servers that have been running on the domain for about 5+ years. It's full of old A records and as a result, a single IP address (for example may point to 3 or 4 different computers. I see lots of records with old timestamps (2017, 2016 for example). Although I am tempted, I don't want to assume they are stale (or incorrect) and blindly start deleting A records.

'Scavenge Stale Resource Records' is enabled. No-refresh interval is set to 7 days and the Refresh interval is also set to 7 days. I am assuming the servers are using the default security settings (I am not the one who set them up). Dynamic update is set to 'Secure only'. IPs are assigned using the Microsoft DHCP server on the same domain.

(I am only referring to DNS records added automatically, not static records). So if a computer was decommissioned 3 years ago (for example), why is the A record still there?
What would you recommend as the best way to clean up to non-static A records on this DNS server?
I'm trying to get an HP 2920-48G Procurve switch setup with multiple VLANs that received DHCP from a Server 2012 R2 server on one of the VLANs. I'd also like one of the VLANs (VLAN 30) to be restricted from seeing any other traffic and only able to route outside.

I am having a difficult time getting DHCP to work on any VLAN other than VLAN 1 and that only works because it is on the same subnet.

The DHCP server IP address is
VLAN 1 is
VLAN 10 is
VLAN 20 is
VLAN 30 is
VLAN 40 is yet to be determined

Internet firewall is

Below is my config. I have recently updated the firmware on the switch to the latest stable release from HP. Any help would be greatly appreciated.

Startup configuration: 8

; J9728A Configuration Editor; Created on release #WB.16.08.0001
; Ver #14:

hostname "HP-2920-48-1"
module 1 type j9728a
trunk 48 trk1 lacp
ip route
ip routing
snmp-server community "public" unrestricted
   ip address dhcp-bootp
router rip
   redistribute connected
vlan 1
   name "DEFAULT_VLAN"
   no untagged 1-15,17-47
   untagged 16,Trk1
   ip address
vlan 10
   name "Business VLAN"
   untagged 1-15,17-47
   tagged Trk1
   ip address
   ip helper-address
Cisco R setting DHCP-PD , right method is set a WAN pre 64 bit hex IPv6 left the local mac layer identify ?

The using R wire Cisco only allowed a NAME just  , example 2002 ,  which was on Rv042G set DHCP-PD 2002:: Prefix , is the current Router under previous Rv042G stored at the Server of Cisco caused this ?  Or the apply wont' be processed going on ?
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Dear All

               i have a server 2008 with DHCP enabled, and i found that DHCP show all ip range has been released out, but actually i see some ip within the range are still available and has not been leased, any idea what caused such issue ?


I have two DCs acting as DHCP servers (Windows server 2008 R2). Devices connected to an access point (Unifi ap pro) gets an IP address from the DCs.

How do devices know which dhcp server they should get its IP address?

How can I make the DHCP servers redundancy so if one DC goes down, the devices are still able to get an IP from the secondary DHCP.

I am looking to change my dhcp server from domain controller to cisco firewall.  I have enabled dhcp server  on cisco 5510 and turned the dhcp server service off on the domain controller.   When I restart the pc expecting it to get ip from cisco it does not work.

However When I turn back on  the dhcp server service on the server (win 2008) everything is fine.

Attached is a pic of the cisco dhcp server settings

I am wondering am I supposed to do something else.  I thought when I enable dhcp server on the firewall .. it will automatically assign ip.
We have an Allworx phone system, with HP and Aruba Procurve (PoE) switches connecting the phones and servers. We have a problem with intermittent one-way audio- I think I know the cause but I don't know how to solve it. Our phones are supposed to obtain IP addresses in the range from the Allworx server. I have found that a small number of phones randomly obtain IP addresses from our Windows DHCP server in the range The VoIP VLAN is set to 200 and the Windows distribution VLAN is set to the default (I believe it is numbered as 0 on the switches). Every time a phone has the one-way audio problem, it is in the Windows distribution range. Not every phone in the windows range has the problem, but every time a phone has a problem it is in that range. We don't want to expand the VoIP traffic into the Windows range. But I think the problem is the phones that get the wrong IP addresses. It is not limited to a set of phones, but there are usually about 5 or 6 that could be any of 45 phones at this site. All phones are statically set when they are issued to use VLAN 200, and the problem occurs regardless of phone or switch port. Users are not moving equipment around, so that is not the cause.

So the problem is that DHCP appears to be bleeding into VLAN 200. The PC's on the DEFAULT VLAN never get IP addresses in the network. Switches are up-to-date with firmware. We have this problem at other sites as well, but one site …
We have a printer issue that is having an issue connecting to a network via wifi. We have DHCP setup on our Sonicwall firewall, but we are not using this for the printers, we have setup a range of IPs outside of the DHCP scope, to be used specifically for these printers. One of the printers ( they are not able to print to, nor is it pingable. If we change it to DHCP and it gets another IP, we can print and all is fine. If we assign it another static IP from the range I mentioned above ( it prints fine as well. There JUST seems to be an issue with this one IP ( - Like I mentioned, no one else would be getting this IP because it is outside of the DHCP scope, and there is no other device in the building that is statically assigned this IP. Has anyone seen this type of issue? Any suggestions?
we are moving to Server 2016 from Server 2012- we have 2 domain controllers both running DNS DHCP AD etc- one of them is configured as a radius server for VPN connectivity

Can both of them be configured so that they both can be listed in Cisco ASA as radius servers? or is this one of those there can only be one?
We are getting rogue IP addresses and when that is happening we are having intermittent connectivity.  We have 2 dhcp servers, one windows for school and one through Sonic wall for rest of complex.  we moved our servers to a new server room and started having this issue.  We didn't change anything else.  We have unifi wifi and witches, NO USG and cant figure this out.  I have a meeting I have to be at in 13 minutes, so please ask away and I will get you as much info as I can.  We have restart we have done as much as we can think of and it is mostly one set of Atom Win 10 Notebook/Tablet computers having this issue.  And connectivity is noticed with our HVAC, automated logic.  Also if I  ping my cloud key, I get about 1/3 that don't return.

Also, school is on a 10.10.X.X and church side is  we need to be clear what is behind content filter is the reason for the two subnets.

The screen shot is what we get when the Atom win 10's loose connectivity.

Remember I just a priest and I do this cause we are a poor church with a school, so be gentle...

Thanks again.

My company currently it's moving to a new phone system and we are stock. our DHCP it's set to IP Scope 192.168.16.xx and I created a second Scope 10.11.0.xx so it can connect via VPN tunnel with the VoIP system of our another office (we are in So. Cal and the other office in Florida) now, To my knowledge I need to create the scopes and the services on DHCP so I can setup the relay to ensure that traffic can go from the 10.11 network using the 192.168 network as gateway and at some point  create a VLAN in my switches to route.

I did all the first part until before the VLAN part, I have some problems.

1-Computers on my Scope 192.168.16.xx are registering on the 10.11.0.xx I need to know how to stop them from doing that, I need to keep them alive but without merging

2-Do I need to create a vlan to route all my VoIP traffic ? we have layer 2 switches and the router it's managed by our ISP or Do I need to setup a a new port in my firewall with that subnet routing all traffic from 10.11 to the public IP

I have a VM running server 2008 R2 as my DHCP I have 2 virtual NICS installed one running on 192.168.16.xx and the other on 10.11.0.xx
I have RRA installed with IGMP installed, and my gut tells me that I did something wrong

I have not done something like this in years so if there is anyone that can give me some guiadence I will really appreciate it.

I am trying to configure DHCP options for HP Thin Clients to boot into PXE. I am working off this documentation from HP


I understand about PXE, and what I don't really understand why HP says 43 and 60 should be removed

And want to do is have these options set in powershell script because we have several different subnets
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I had this question after viewing Cisco ASA 5505 host license limit workaround and dhcp lease time.

In my office network some end users cant access the internet even though they are connected to the lan.

Is there a workaround ? I am using Cisco asa 5505 with 50 license limit.
I use different netsh commands to run individual back ups of DHCP servers.
For example:
netsh dhcp server dump > \\\dhcp$\Area1\dhcpcfg.txt
netsh dhcp server export \\\dhcp$\Area1dhcpdb all
netsh dhcp server dump > \\\dhcp$\Area1\dhcpcfg.txt
netsh dhcp server export \\\dhcp$\Area2\dhcpdb all
I have to go on each server to run this
Please indicate a power shell command I could use to run once and back up all my dhcp servers
Windows Server 2012 R2 DHCP - Left hand Reservation list is not in numerical order

Hi, I have two DHCP servers at one physical site (Failover setup) that don't show the DHCP reservation order in numerical sequence, all my other DHCP servers at other sites however do show them in numerical order.
We reserve our IP addresses against MAC addresses, so it can be annoying trying to find the IP reservation in the left hand list.
The right hand column can be easily sorted in numerical order but that doesn't help, as all properties are set in the left hand column.
Any ideas on how to correct this ?
Have a small environment with no networking engineers. About 30 laptops on and off the wired and wireless throughout the day. It makes it difficult for deploying applications and scripts to them (like with PSexec or PDQ). Both DHCP and DNS are on 2 windows servers replicated.
Is there a recommended approach to updating a laptops IP when it goes from wired to wireless faster?
I have a VLAN network that is out of IP addresses. We have to stay on IPv4 for a number of reasons, so I think the best way to fix the issue is to add a subnet range. The current subnet is and I would add a subnet, then move all of the statically assigned devices to that network.... which should avoid the complexities of setting up DHCP and IP helpers on the switches. There are some other subnets and VLAN's configured as well, and the switches are stacked. The switches are Aruba L3 switches. Here are the VLAN setups- Subnets's 3rd octets match the VLAN ID for the 192.x.x.x networks:
VLAN ID         Name              IP
1                       DEFAULT
         Tagged:  1/37,1/43-1/44,2/45-2/48,3/4,3/6
         Untagged: 1/1-1/10,1/12-1/17,1/19,1/21-1/34,1/36,1/38-1/42,1/45-1/48,1/A1-1/A2,2/1-2/44,3/1-3/3,3/5,3/7-3/24
2                       VoIP                 172.16.x.xx
         Tagged: 1/1-1/48,1/A1-1/A2,2/1-2/48,3/1-3/3,3/7-3/24
         Untagged: 3/4,3/6
5                       Facility2 
         Tagged: 1/17
         Untagged: 1/11,1/18,1/20,1/37
7                       Facility3 
          Tagged: 1/45
          Untagged: 1/35
8                       Facility4 
          Tagged: 1/46
          Untagged: 1/43

So, I am not touching the VoIP network.
The 5 VLAN is the one I have set up, but I am unclear on the whole tagging versus …
Need some help in tracking down an IP conflict that I have.  DHCP servers are Windows 2016 servers (setup in a failover scenario) but I have a MacBook that has had this happen twice in the last month.  He will get a popup saying:

Another device on the network is using your computer's IP address (  

I'm not sure if this IP was for his wired connection or his wireless but only seems to affect his MacBook.  With DHCP servers there shouldn't really ever be IP conflicts (unless someone adds a static IP which I don't think this is the case here - it could be but I doubt it).  In DHCP servers, logs don't show anything...

Anyway at this point to track down what grabbed the .204 IP?






The Dynamic Host Configuration Protocol (DHCP) is an auto configuration protocol used on IP networks and an extension of the Bootstrap Protocol. DHCP allows for computers to be configured automatically to communicate with each other over an IP network without the need for manual setup by a network administrator. The implementation of DHCP relies on a DHCP server to hand out network configuration information to DHCP-capable clients that request an IP address (and other information required or useful in communicating with other devices on an IP network). In addition to an IP address, common configuration information served over DHCP includes a default gateway, subnet mask and DNS sever(s).