DHCP

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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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Cisco 8851 phone not detected into the network. When I plug the phone directly into the switch in registers just fine in call network. Back at my work station. I plug the computer into the corresponding port and it works fine. Plug the phone in, and it get PoE just fine, but cann't see the network. I have cleared port-security on the switch. The phone is set to recieve DHCP just fine. The settings seem to be correct as I can plug the phone directly into the switch and the phone registers in Call Manager just fine. Plug it into the corresponding port back at the work station, and no go.
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We have s small network with 30 computers , fileserver, two DC's, Hyperv, Cisco Switches and routers. DHCP is currently running of of the ASA Cisco Router . Should we switch that to one of our  domain controllers ? Not sure what the pros and cons are?
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We’ve been chasing an issue we’ve been unable to find a root cause for.  The symptoms are that random computers will lose their dynamic IP address and grab a 169.x.x.x IP address. They will however keep their default gateway settings.  If the user unplugs their network cable and reconnects it, the computer grabs the same DHCP address and works fine. I have tried reservations with the same issues. Happening at 3 different AD sites on different Vlans. I have ran wireshark and found no other rougue dhcp server listed besides my own. Happening on Win7/10 Hp/Dell. On other machines never have an issue plugged into the same switch. Scratching my head on this one.....
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Hello :-)
I am configuring dns scavenging in my dns / dhcp. currently the dhcp lease is 6 days, so according to the question https://www.experts-exchange.com/questions/29093013/DNS-Scavenging-Best-Practice.html I've defined the no-refresh and refresh values for 3 days each (50% dhcp lease). So the DNS option "allow automatic deletion of obsolete records" should be set to same dhcp lease (6 days)?

dns.JPG
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DNS scavenge with multiple DHCP lease times

We have the following configuration. Also attached is our DHCP configuration @ the top level. We have the default Server 2012 R2 options, "Dynamically update DNS records only if requested by the DHCP clients" with " discard A and PTR records when lease is deleted" ticked. We have credentials set for DNS dynamic update & our DHCP servers are added into the DNSUpdateProxy group. Scopes & counts as follows:

9 DHCP scopes with 1 day lease
12 DHCP scopes with 2 day lease
11 DHCP scopes with 8 hour lease
105 DHCP scopes with 8 day lease

Have done a lot of reading about the refresh + no refresh ideally being the same as the DHCP lease time, but assumption being DHCP lease times are same for all scopes. Our scenario is they are not, & so not really sure on the impact of different scavenging options

Majority are 8 day lease, so reading many blogs it mentions this should ideally match the total refresh. So values of 4 & 4 for no refresh & refresh, but then what is the impact of this on our scopes with 1day, 2day & 8 hour leases? Suppose the risk is they end up with duplicates until the zone is scavenged?

This is where I am thinking we should maybe configure DHCP to "always dynamically update DNS records" but they don't know if this actually required. My thinking is that if address is assigned to another computer DHCP can update DNS & we shouldnt have duplicates, then configure 4 + 4 days for scavenging. Or is this not …
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I have a DHCP server with two IP scopes.  We also have VOIP phones that use a separate VLan and receives their IP addresses via a DHCP server on my router.  We had some problems with the VOIP Vlan and was forced to put all the phones onto the default DHCP server with my computer devices.  Once we fixed the VLAN issue, we changed the configuration in the phone which put all the phones back on their own VLAN, thus releasing all the IP's leases from my default DHCP server.  This morning, I got a warning that my DHCP server was using 88% of the IP's, looked at the server and all the phones leases were back.  I know these phones are not using these IP's because the change is manual.  Each phone had to be put back onto their VLan through a manual setup.

My lease time is 6 hours, so I deleted all the phone devices that showed up, but does anyone know why after a week, they showed up and started pulling IPs?
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Windows Server 2016 DHCP server stopped handing out IP addresses.  I'm receiving a ton of the following error in the event viewer:

  • PTR record registration faor IPv4 address [x.x.x.x] and FQDN [computer name] failed with error 9017 (DNS bad key)
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I want to setup a single scope to hand out addresses to all of my student laptops....640+ laptops.

Using Windows 2008r2 server.

Is that possible?  

Thanks!
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We currently have 13 Access Points controlled by a Cisco WLC 2504.  We have two WLans - one for Guest and one for employees.  Our employees use WLan 1 which accesses the DHCP server on my domain.  The Guest uses WLAN 2 which access the DHCP on my router.  On my DHCP server we have two separate subnets with plenty of IP's available.  Due to some routing issues, I needed to use most of the available IP's for phones.  Once that was cleared up, those IP's are now free again.  My problem is that we are now unable to get an IPV4 address from the employee access point.   We have two subnets, so there are plenty.  What do I need to do to fix this issue.  Interesting enough when I create a separate vlan pn my router, any device connected to the employee access points gives me the error message - no internet access
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I'm currently replacing (NOT migrating) an old Windows 2003 SBS server (running AD,DNS, DHCP & File Sharing) with a new 2016 Essentials server.  The current 2003 SBS server is currently only server on the network with about 5 users, so it's a small implementation.   Email has been moved to O365 so nothing needs to be done with mail services.

Since the 2003 AD is cluttered with junk from over the years, I'd like to setup the new 2016 server with a completely new domain and NOT joining it to their existing 2003 domain. I'll setup the DHCP & DNS configurations, and the few users and shares can be added from scratch on the new server, then unjoin the workstations from the old domain and join them to the new domain.  

Also, after the new server is on the network and the workstations are joined to the new domain, I'd like to keep the old server on the network so I can copy some files to the new server.

I understand that since the old server is running DHCP & DNS, I'll have to turn those services OFF on the old server once the new server is on the network and handling those services.  I'm sure there are other caveats that I'm not thinking about.  

Has anyone done this type of server replacement (NOT a migration), and if so, can you provide any information or "gotchas" that I need to watch for?

Thank you.
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I have installed a new firewall and changed the gateway IP in the process for a small network. now that it is different, i added the new ip in DNS and changed it in DHCP in my server. for some reason, i am not able to access my sonicwall from my server. i can not ping it or get to it from the web browser. the other devices on my network can get to it just fine and are all on the same switch. i put in a new switch because there was a bad port on the old one, thinking it was just a switching issue. i have disabled my firewall and all the antviruses on my server and still cannot connect. my dns is not functioning correctly because of this as well. any ideas? Im at a loss
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We have a child company that has the need to separate its IT infrastructure. The child company is still on the same campus, but in 2 different buildings. Would it be feasible to use a separate Vlan and create a separate domain with its own domain controllers, dhcp server, etc.? Would you do it this way or separate the other buildings completely with their own entire infrastructure (obviously way more expensive). Thanks for your input in advance.
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I have a Server Essentials 2016 installed. DNS is installed. DHCP is installed and a scope is setup. the router is set as the gateway. I turn DHCP off on the router intending for the server to handle this but I am missing a piece(s) of the puzzle because it doesn't work. This is a test setup and I am using a home router for learning purposes.
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We have a DHCP server with multiple scopes (VLANs). We have option configured for VoIP phones too. It seems to be straight forward to configure as per MS, but anything can happen while we try to configure!. Any of you had any problem of making to work?.  Do we have to do anything on the network equipments to make this work?
I am looking for EE/KB article . I would appreciate if you could help me on this.
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I am unable to access our Cisco ASA 5505 via ASDM because we don't know IP address. We were setting up the ASA to act as a DHCP server and made a mistake and changed the IP address. We have the credentials to access it via the ASDM but without the password it won't work. I've tried to access it using Putty but it's asking for a password we don't have.  Is there a way to figure out what IP it is set for?
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Hi Experts.
I'm trying to write a PowerShell script that would tell me if all the physical Wired interfaces (ignoring virtual interfaces generated by VPNs and Physical Wireless Interfaces) are set to DHCP, not only on the IP Address, but also on the DNS Side, and set it to DHCP, if they are not.

I have the first part nailed down, It's fairly easy:
$adapters=$(Get-NetAdapter -Physical |Where {$_.MediaType -eq "802.3"})
foreach ($adapter in $adapters){
    if ( -not $(Get-NetIPInterface -InterfaceIndex $($adapter.ifIndex) -AddressFamily IPv4).Dhcp -eq "Enabled"){
        Set-NetIPInterface -InterfaceIndex $($adapter.ifIndex) -Dhcp Enabled
        Set-DnsClientServerAddress -InterfaceIndex $($adapter.ifIndex) -ResetServerAddresses
    }
}

Open in new window


That part was fairly easy to figure out.
The DNS part eludes me.
I can get the DNS Server address that is assigned to the interface like so:
Get-DnsClientServerAddress -InterfaceIndex $($adapter.ifIndex)

Open in new window


But I have no way of knowing if it was assigned via DHCP or not, even if I use the |fl switch to see all possible attributes, all I get is this:
InterfaceAlias  : Ethernet

InterfaceIndex  : 12
AddressFamily   : IPv4
ServerAddresses : {192.168.81.201}

InterfaceAlias  : Ethernet
InterfaceIndex  : 12
AddressFamily   : IPv6
ServerAddresses : {}

Any Ideas?
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Windows 7 Pro logging onto a Windows 2016 domain is very slow - i'm talking 10 minutes or more with the "Welcome" screen. Each user was configured with a roaming profile but I've now reconfigured that by removing the profile link in the user's AD account. I thought roaming profiles was the problem but still the slow logins persist. Nothing much seems to be going on while it's at the welcome screen, it just seems to be waiting for something.
Any clues on what could be causing this please?
It's a simple setup, Windows 2016 DC running DHCP and DNS and a bunch of PCs running Windows 7 Pro. DHCP is set to issue DNS of 192.168.5.3 and 8.8.8.8
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We have had a lot of people in & out of company lately, and can expect a lot more of this over the next month or so, causing my DHCP pool of addresses to be eaten up rather quickly.
I've added more, decreased the lease time from 8 days to 3, but is there a way to revoke(?) any addresses that haven been inactive in the last 3 days?
Also, I had noticed several that had BAD ADDRESS next to them. What's up with that?
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I have 3 building that are using DHCP on my sonic wall.  I wanted to setup a dedicated DHCP server in the network 192.168.0.5.  I have gotten it to work great for the 192.168.0.X range.
I have a connection going to another building that is using IP address's of 192.168.30.X.  When I use the DHCP on the Sonic wall it works (I did not setup the sonic wall)  I setup a new scope on my DHCP server for 192.168.0 and 192.168.30, I disabled the DHCP on the SONICWALL and thought it would be able find the DHCP server in the subnet of 192.168.30, but none of those devices are seeing it.  That mean I missed a setting on the Sonic wall that routes DHCP to thew subnet for 192.168.0.  If possible can I get some assistance in this configuration?
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Greeting Experts,

I need help setting up a PowerShell script to collect all of the Mac address currently blocked in DHCP ( i.e., Mac Filtering). My organization has some DHCP Server (over 60) located at each one of our sites. Can somebody help me create a script to query my companies Domain ( i.e., all the DHCP servers) and come back with a list of filtered mac addresses?  Can somebody help me with this task.... thanks
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Hello all,

I have DHCP set up to update DNS and discard host A and PTR records after the DHCP lease has expired (without scavenging enabled)  I was wondering if there was a way to "set" how frequently DHCP removes the records?  I can see that the DHCPsrvlog is generating around 12:00 a.m daily and can see it is removing records but I am not able to see when this is happening.  When I test I turn on a client and I can see the dhcp lease and the records in forward and reverse lookup.  Then the lease expires and is deleted but the records stay for X amount of hours, I come in in the morning and they are removed.  Is there a process or event that runs that I can track?  Please remember that this is working without scavenging enabled.

Thank you

Server 2012 r2
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Merge/Consolidate DHCP scope from on 2008 R2 server into the scope of another 2008 R2 server

Hoping someone who has done this on 2008 R2 can shed some light on the process.
I want to merge several DHCP scopes from an existing 2008 R2 server into the DHCP of another 2008 R2 server without causing any issue to any of them.
Both 2008 R2 servers are currently serving as DHCP servers, but for different scopes on either of them and none of them are shared between them.
The scopes are all different so I am assuming a backup on the source server and import into the target server ought to do the trick.
Or do I export individual scopes and then import then individually?
The scopes do have some reservations so those would have to move as well.
Does the source DHCP server need to be de-authorized, before I import its scope information into the new one?
As always many thanks in advance for insights.
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I'm trying to connect a Watchguard T30 to an AP320 through a Cisco Catalyst 2960.

I'm able to set up trunking on the Cisco so that I can see the AP320 through the controller, however when I connect to the WLAN I get no DHCP address, and I can't get online even when I hard code the IP. Based on some logging information I've seen on the Watchguard, it almost looks as though the Cisco switch is sending packets to the wrong gateway address.

It looks like when a device was requesting an IP on the VLAN 192.168.5.1/24 subnet that request was sent to the lan 192.168.1.1 gateway.

I'm extremely new to Cisco so it's entirely possible I'm missing something obvious, but when the VLAN's are set up on the router and then trunking is configured for those VLAN's on the Cisco, is there a place where you need to specify what Gateway to use for each trunk?
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i just want to understand 1 thing

i see a citrix environment in one company

90% of users are using xenapp having non persistence desktops.

i see seperate DHCP scope defined in one of citrix servers.

when i do ipconfig, i see address coming as 10.x.x.x

we have on premise AD where users are synced through AAD sync to office 365 and mailboxes in office 365

outlook is 2010 and is configured on premise in stalled on xenapp and published to studio

my question:
there is group policy called outlook GPO for outlook users whose cache files shoudl be enabled

i know this is bit vague

but if DHCP scope is defined in citrix server and dekstops are getting IP'S from there

how come group policy called outlook GPO is working for outlook users

when there is no DHCP scope defined in AD

I MEAN HOW that GOP is geeting affected in outlook where citrix has its own DHCP

is that some thing AD has in its users and computers accounts for cirtix servers and then it si working?
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I have a 4 machines, all running windows 7 pro. They are all on the same domain connected to a server. The server acts as our domain controller and also our DNS server. A router handles our DHCP.

I have 2 machines that are intermittently dropping server connectivity. These two machines will be referred to as 1 and 2.

Machines 3 and 4 have no connectivity issues whatsoever.

Machines 1 and 2 will work all day and then come morning, they don't have access to the mapped drives on the server.

Once they are restarted they connect back and everything seems good.

I have checked both DNS and DHCP settings on all 4 PC's and they're identitcal. DHCP seems to be working as I can release and renew IP's on all 4 machines, and I also checked the DNS by pinging IP's outside the network and also by their FQDN's. (google and bing)

Any ideas why machines 1 and 2 could be losing connectivity?
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DHCP

10K

Solutions

15K

Contributors

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).