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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It is a SBS-2011 Server. I will create a new DHCP reservation and set the reservation name to "GSMPC-11 N". Then it looks like when it goes active Windows changes the name to the computername.domain i.e. gsmpc-11.gsmetalinc.com

   Well..... what is the point in even creating a reservation name when Windows changes it to computername.domain automatically? Is there any way to stop it from changing the reservation name?
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Hello,
I have DHCP failover cluster configured (hot standby mode) and its not functioning good.
Sometimes workstations need to restart to pick up IP address.
So,I plan to remove second(standby)dhcp host and remain only one dhcp server
Is this what I need to do?Delete dhcp failover and unauthorize stand by dhcp host?Scope remains?
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Hello Experts,

I want to test DC site failure between 2 sites connected via a leased line. Both sites have 2 dcs each on Win server 2008. Both sites can communicate with each through our leased line.
Both sites have their own DNS and DHCP servers.  

The plan is to unplug both DC on one site and see if those on the other site take over and vice versa. This will simulate a complete DC site failure.

As I understand we will have to move our fsmo's role over to the active dcs when the others are taken down and also DHCP and DNS. If we did have a complete site DC failure on site1 I can I setup a DHCP and DNS in a disabled state in site2 ready to take over in case of an emergency.
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One of our client has a strange issue with migrated DHCP. They are getting BAD_IP address issued by DHCP.
Basically they exported the old DHCP and imported to new DHCP server.
Any help would be appreciated.
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Is it Enough to configure DHCP Snooping without ARP Inspection

I would like to know if it is efficient to configure just DHCP Snooping and do not configure ARP Inspection.
 I thought DHCP snooping is enough to avoid having Rogue DHCP in the Network. So what  else that ARP Inspection adds to the DHCP Snooping ?

Thank you
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I recently split our DHCP addresses between to DHCP servers.  One server has a scope of the first 127 addresses (1-127) of a network, and the other server has the remainder (128-253).  Things appeared to be working well.  Both servers lease addresses in the proper ranges, and I can ping them.  However, on two clients that host web interfaces for various programs, the web interface will not open.  They do open on the localhost.  Are there any ideas about what could be causing this?  I believe both of the clients in question have the proper DNS entries.  However, one client is set to get its address by DHCP and is assigned a reservation.  The other client has a static address.  I have added A and PTR records for both.
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Had to reboot a ESXi 5.5 server.  It decided that it wanted to pull an DHCP ipv4 address.  When trying to set it back to static. it tosses out an error that it cant save it because of iPv6.  We have that disabled.  It can pull a DHCP address no issue.  Never seen this before.  Where do i start?  

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Dear Experts
Installed windows 2016 standard and configured it to function as domain controller, DNS server and DHCP.  It is observed the after promoting the server to AD domain controller the IP of the serer in the primary dns changed to local host I mean pointing to 127.0.0.1, manually changed to the actual IP.
While creating the forward and reverse zone had selected “do not update dynamic updates”
Following are the issues faced
1.      While joining the client system that is windows 10 pro to domain it accepted to join but message shown “preferred dns could not be changed” and then after reboot able to login with domain user. Please let me know where I am going wrong
2.      When the user logon and click on network browse the domain controller can see netlogon directory but does not show the user home directory, please let me know what I have missed.
3.      I made the normal user a member of domain administrator group in the server and then logon to the client system with this user but he does not get admin privileges when click on network to change IP address it prompts for logon and password but it does not allow administrator login to client system nor it does not consider this user as administrator who is actually member of domain admin group  
4.      Before joining the client system to the domain controller is required to create A and PTR records manually and then after join the system to domain
Please help me understand and suggest the steps to resolve the above 1 to 4, this…
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We have be experiencing issues with the DNS servers that are being setup on DHCP clients. We have recently setup and configured Cisco Umbrella. The VA's have been setup and all DHCP scopes have been updated to use the VA's for DNS. All was working well or so it seemed but we started noticing DNS issues. ipconfig sometimes shows the correct DNS servers (the VA's) and sometimes shows the internal DNS server. The DNS servers change in between lease changes. Any advice on troubleshooting would be greatly appreciated.

Regards,
ABBEadmin
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I've setup a Server2016 test environment. Contains a VPN server, NPS Server and a DC. I connect to the VPN fine. Pulls an IP from the defined DHCP scope. I can ping any internal resource, but i cannot navigate to any shares. I've gone as far as completely shutting off the windows firewall on the  server and workstation(Win10) sides, still cannot navigate to a any shared folders on any of the 3 servers. Ive made sure the DNS entries are there. Any ideas as to why i cannot browse to the server by IP?

EX. from an external network connected to the VPN
ping 192.168.17.50 - get 4 responses
ping testdomain (DC server name) - Could not find host testdomain
nslookup 192.168.17.50 - Server: testdomain.test.local
                                           Address:  192.168.17.50
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I installed a domain controller with DHCP. The DHCP configuration was exported from old server and imported to new windows 2012 DC.
The DC NIC was checked for IPV6 and IP4. We are not using IPv6. DG is not enabled for IP v6.
The DHCP is not binding to the ip version 4 nic. The error with event id 10020
" This computer has al least one dynamically assigned ip v6 address. For reliable operation you should only user static ip ver 6 address"
If i uncheck the IP v6 on the NIC then DHCP works.
Any suggestions?
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We have H3C layer 3 switch. I find sometimes staff will bring their laptop / mobile to connect our network through our DHCP on server 2008.

We know their MAC address. Is it possible to deny any network on a particular MAC address on H3C switch?
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Wired users getting 192.168.1.x IP address.  Instead of 10.10.x.x
Not sure what happened.   Not all the users tho.  Any ideas?
ipconfig /renew /release not helping.  
Need some help troubleshooting.
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DHCP shows red arrow, see pic, what does this mean?
dhcp.png
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We installed DHCP and DNS on a Windows 2012 Domain controller. We disabled the IP V6 option in the TCP/IP settings since we do not use.
We rebooted the domain controller and noticed the DHCP for IP v4 stopped working.
We disabled the IP v6 option and restarted the DHCP service and it worked.
We rebooted the server to make sure that DHCP functions after reboot, but, this time DNS was not able to function correctly because we disabled IP v 6 even though
IP v6 been around a long time and you must have come across this issue. What is the fix for this?
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Get-DhcpServerV4Scope | Where-Object -FilterScript { $_.State -Eq "Inactive" } | Remove-DhcpServerv4Scope -Force -Passthru

1.Kindly provide equivalent NETSH DHCP command as like as PS CMD mentioned above

2. equivalent  power shell command  to run windows 2008 r2 server above command not running 2008 R2
Or

3. My requirement is to delete all inactive DHCP scopes  using netsh or PS(2008 R2) by excluding active one
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A fist time experience for me happened yesterday. My environment is using static IP Addresses for everything; no DHCP. A client was mistakenly assigned the same IP as our primary DNS server and everything in the environment went haywire. There has to be a way to prevent that other than the obvious. Any knowledgeable folks have an idea?
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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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Hello looking for some help on this. My ISP did an update that made it necessary for us to update our outside IP address config setting from static to DHCP. I change it and give them the Mac address of the ASA and it usually after they update the table it pulls the correct IP address. That part seems to be fine but for some reason, after the change, my site to site VPN will not come back up. Nothing else has changed. Any ideas on this? 

ciscoasa# sho run: Saved:ASA Version 8.2(5)!hostname ciscoasadomain-name 111.comenable password w3iW.W8jLtqmhFnt encryptedpasswd 2KFQnbNIdI.2KYOU encryptednames!interface Ethernet0/0 switchport access vlan 2!interface Ethernet0/1!interface Ethernet0/2!interface Ethernet0/3!interface Ethernet0/4!interface Ethernet0/5!interface Ethernet0/6!interface Ethernet0/7!interface Vlan1 nameif inside security-level 100 ip address 10.13.13.1 255.255.255.0!interface Vlan2 nameif outside security-level 0 ip address dhcp setroute!boot system disk0:/asa825-k8.binftp mode passivedns server-group DefaultDNS domain-name 111.comobject-group network obj_anyaccess-list NONATACL extended permit ip 10.13.13.0 255.255.255.0 192.1.1.0 255.255.255.0access-list VPNACL extended permit ip 10.13.13.0 255.255.255.0 192.1.1.0 255.255.255.0access-list OUTSIDEACL extended permit icmp any anypager lines 24logging asdm informationalmtu inside 1500mtu outside 1500icmp unreachable rate-limit 1 burst-size 1asdm image disk0:/asdm-731-101.binno asdm history enablearp timeout 

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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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WDS Deployment issue

In my environment we have two network. One for servers and other for clients. Let's  assume servers network is  10.0.0.0/24 and client network  is 192.168.1.0/24.I already deployed the WDS in 10.0.0.0/24 network. our AD,DNS and DHCP  is located in 192.168.1.0/24 network. Now  when I am trying to boot the client using PXE, client can't access WDS.


So how to resolve this issue.

If everything(WDS,AD,DNS,DHCP and client) in same network its working fine.
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Hey! I have a router problem. On last saturday, i got the new 1000mbit/s internet in my house. My ISP(called Digi, in Hungary .) Gave me a Huawei(Huawei EchoLife HG8242-B,) modem/router(?). I bought on monday a new TP link AC1200. BUt i was experiencing internet drop issues. (it lost connection after 30mins, and keeps doing that in that interval.) So I called my ISP, they came to my house on wednesday, and told that, the problem is in my router. So i took it back to the shop, and bought a new TP link AC1750 V4.0 on Thursday. But the problem still appear, and I've tried everything. Dhcp change, MTU size change, frimware upgrade/downgrade, DNS change but it still drops the connection on WIRED. The problem appears on every WIRED computer, at the same time. Before first my ISP came to my house, the Huawei was in Dinamic IP mode, but my ISP changed that to bridge mode, so now the connection is now, a PPOPE one. Problem still appears, every time, and ISP keep saying, there is no fault at their end. But it'S possible to get 2 wrong router? My ISP will come today too.  SO what should i change  to finally forget this problem?
The strange  thing is , from an old TP link 941N router, everything works fine.
Now, what could be the issue?
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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)?

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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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DHCP

10K

Solutions

14K

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).