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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Hello Experts-

I am having some network issues starting a few days ago.  Initially I thought it was a DNS issue as the webpages would fail to load then immediately load once refreshed.  I noticed a few DNS log errors in the even viewer as well.  Upon checking the DNS server and NIC it seems to be ok.  An nslookup will sometimes point to the correct server and address sometimes and others it will time out.  Next I started looking at connectivity from the servers and the weird thing is we still have internet connectivity, albeit not perfect but it will load the pages 90% of the time but ping results to the DHCP and DNS (separate servers) are intermittent with a 50% - 75% loss rate, other times they will ping perfectly.  Pings to the gateway seem to always go through.  I am a little befuddled on what is going on.  I am leaning towards the switch that everything is connected to is having an issue but that'd be odd since its less than 6 months old... not impossible though.  Both servers are Windows 2008, the majority of the clients are Win7 and Win10. Any thoughts would be appreciated.  Thanks!
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Hello,
Does anyone know how I can fix this issue with our Exchange 2007 on Win2003 server?  Beginning early this morning all connections from outside our LAN are lost or down on our Exch2007 Hub Transport server.  After checking all services it came down to restarting the DHCP client service and the Hub Transport server is back online.  It is very sporadic and I can't seem to find out how to fix this.

Outside email stops arriving and I'm unable to access the Exh2007 server via iPhone or OWA.

Thanks,
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Hi,

Recently had a perculiar issue with clients on one of our customers networks that stopped being able to lookup names on the internal network, losing network drives, gpo etc as a result.

DHCP is served by windows server 2008 DC with DNS service also hosted on this with the relevant pointers to this set up in DHCP.

We ended up having to statically set the DC name in the HOSTS file until I looked at this onsite this morning, I noticed a nslookup was resolving the router as the dns service instead of the DC. Powering off the router and running the same nslookup and it resolved to the DC. DNS and DHCP were both disabled on the router.

I made a change to the Interface in DNS as it was set to 'Listen On All IP addresses' I changed this to 'Listen on specific IP' which was the IP of the DC(Itself). Flushed the cache on the clients, restarted them they got the gpo, drive mappings, and I could resolve the server by name.

However, a nslookup still resulted in the router name rather than the DC name, despite obviously being able to resolve hosts on the network.

I then disabled ipv6 on one of the clients nics and hey presto a nslookup resolved to the IP of the DC, if I re-enable ipv6 on the nic it reverts back to resolving the router.

My thoughts are that the client isn't able to resolve the DC by ipv6 so it is reverting to the server for some reason, perhaps because of forwarders/root hints set up in DNS.

They are up and running again but I have noticed …
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We are replacing our DHCP server and have come across a problem I'd like expert advice on.
 - Our current DHCP servers (DC1,DC2) are providing leases without issue.
- We have configured new DHCP server (DC3, DC4)  to replace these servers.

After deactivating scopes on DC1/2 and activating on DC3/4 we are finding the following (after ipconfig /release & renew);
  • Clients on the same subnet as DC1/2 obtain leases as expected
  • Clients on a separate subnet/switch timeout when trying to contact a DHCP server, respond OK once DC1/2 scope is re-activated

I have checked a related switch and there is no ip-helper command configured. My question is - can anyone explain why this would work with DC1/2  and not DC3/4?

Thanks in advance
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hi

i'm working with a deployment tool that handles unattend install for non-m$ oses and wish to use it to deploy windows hosts

anybody knows how to associate a mac address with a specific sysprep.inf or unattend.xml file so i can set stuff such as the computer name, ip, routes.... automatically ? or maybe set these in dhcp but make them permanent through a script. ( using dhcp in production environments is prohibited at my location. please don't debate : not my call )

i don't need explanations regarding how dhcp options work but rather how to make the installer use this specific file either through said options or possibly by dropping them in a well-known location.

i'm not interested in links regarding windows deployment services which are off-topic. i'm emulating said services, not using them.

i'd also or alternatively like to be able to specify a custom post-install script. if necessary i can do the above in the postinst ( by rendering persistent a bunch of stuff learnt through dncp ) but i assume there is a better way

thanks for your help
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I was looking at system logging and noticed that a Windows 7 (or maybe 10) laptop computer at one of our remote sites made nearly 500 DHCP renewal requests in an eight hour period. Is that normal? Are PC's using DHCP normally sending IP lease renewal messages 2 3 or 4 times in a minute? If that's not normal, what would likely be the cause?
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Dear All

I have a new Mikrotik cloud core router, I need some help, please.

Interface one - ISP

Interface Two - Network Switch DHCP Scope 192.168.88.**

Interface, 12,11,10 & 9 Brideged together for DL380 Gen 9 NIC Team DHCP Scope? 192.168.89.**

I would like to be able to ping anything in any of the two networks, but I can't seem to figure this part out and need a little help, please.

Thanks
Alex
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Need to refresh DHCP IP address reassign Needed to command
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Dear experts

My situation is quite complicated.
Generally, I m creating an VPN server.
For different client connect to the VPN Server from different country, I would like to provide different dhcp-range.

I understand that dnsmasq support multiple network.
My question is how I can use the tag indicator and the client will collect the correct dhcp-range in the VPN connection situation.

e.g.
------------------------------------------
# Address range for country1 clients
dhcp-range=tag:country1,192.168.1.10,192.168.1.19,255.255. 255.0,1h

# Address range for country2 clients
dhcp-range=tag:country2,192.168.1.20,192.168.1.29,255.2 55.255.0,1h

# DHCP options given to known clients

# Subnet mask
dhcp-option=1,255.255.255.0
# Default gateway
dhcp-option=3,192.168.1.1
# DNS server
dhcp-option=6,192.168.1.3
# Broadcast address
dhcp-option=28,192.168.1.255
------------------------------------------
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We have a domain controller running Windows 2012 Server and it's also our DNS/DHCP server.  Non Windows devices acquire a DHCP lease, but fail to register in DNS.  Yesterday I added a non Windows device to the network, which immediately showed up in DHCP, but not in DNS.  This morning it finally did show up in DNS.  I added another device today and change the scavenge setting to 1 hour, but it still does not register with DNS.  I do have it checked to dynamically update DNS.

Maybe it tomorrow it will magically show up in DNS, but shouldn't it immediately be added to DNS when a DHCP lease is created?  How can I get this to happen without manually add it?
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Hello,

I moving several scopes from different DHCP server. When Importing the scope I receive the following error:

Error while importing class "Default Routing and Remote Access Class."
This class conflicts with the existing class "Classe de routage et d'accès distant par défaut." An internal error occurred.

I found that the error is related to the language ?? but still did not find a solution.

Any help?

Thank you
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i have 1 default lan and 3 vlans.
setup on our watchgaurd firewall
vlan10 ip address 172.16.0.1/23 dhcp relay to the dns server
vlan 20 ip address 192.168.20.1/23 dhcp relay to the dns server
vlan 30 ip address 192.168.30.1/23 dhcp relay to the dns server

On the dns server i have the 3 vlans with thier own scope and in thier scope options i have the router set to
vlan 10 172.16.0.1
vlan 20 192.168.20.1
vlan 30 192.168.30.1
in the dns server routing and remote access i have the ipv4 dhcp relay agent set to 172.16.0.1, 192.168.10.1, 192.168.20.1, 192.168.30.1

all of our switches have the vlans setup also
any time i connect a pc to a switch that has its port set to any of the vlans it gives a bad ip address, 169....
anything on our defualt lan works

for a while i was getting this error on our dns server event viewer.
IPBOOTP was unable to receive an incoming message on the local interface with IP address 191.168.0.4. The data is the error code.

i restarted and also deleted and created the routing and remote acces dhcp relay agent
I dont get that error code any longer but the vlans still dont work
HELP
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Hi Experts,
I want to be able to use some IP phones on a different vlan on HP procurve switches.
The phones are on VLAN1 192.x.x.x but the vlan the phone is plugged into is say vlan 100 10.x.x.x
I thought an ip helper would be all i needed. My phones are on 192.168.x.x
my normal computers are on VLAN 5 192.168.4.0
the phones do use vlan 1 for the dhcp scope options and changes the vlan to VLAN 2 and then this sends the phone to the Mitel server's dhcp. Our normal network works fine and phones get an IP on the .2 network. I want to add this new network 10.10.0.0 and pc's will be sat on this switch untagged but they need to get to the 192.168 network to get to VLAN2.

it all routes fine and i can ping across the vlans but the phones are not getting an IP from DHCP. I have tried adding an Ip helper but i am not sure where this goes in the config? vlan or switch? Do the switches need to know about the VLAN 1 or as long as the vlan 2 for phones is there should the phone be ok to find it.
Thanks
0
All,

I have a project to use DHCP on Servers.  Has any one done this in their environment, any issues or risks?

Thanks!
0
Hello

We have just rolled out IPAM,

Everything is going ok, except i am not see any AD authentications being recorded only DHCP and NPS.

So we are only seeing user details for NPS authentications, I have ensured audit logging is enabled, but i can not find anything on what could be stopping this.
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I am remodeling four homes.  I have  installed eight port structured wiring systems in all four.  Each wall jack (room) includes one ethernet jack, one cable jack, and one phone jack.  Everything is homerun to the utility room in the basement. Within the wiring cabinet located there, are punch down blocks and patch panels for all wires and cables. I would like to install  in each cabinet, an eight port router or switch to include an integrated DHCP server, and POE  jacks. One of these Jack's will be wired to a ceiling mounted Wi-Fi access point on the third floor in the center of the home. This device should be dual band AC 1200  or greater. Ultimately, the router or switch will be plugged into a cable modem providing Internet and telephone service. I am having trouble finding the router or switch, which needs to be small enough  to fit inside the wiring panel.  I also need an inexpensive access point device.  The cable modem will be mounted by the cable service provider outside the panel.  This arrangement will allow plug-and-play of any wired or wireless device in the home without the need for a PC  based DHCP server arrangement. Has anyone done this? Any recommendations? I need to keep this reasonably inexpensive.
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I migrated my DC from 2003 to 2012 R2 recently, and have been having a real bear of a time with workstation connectivity. 2003 had a clean demotion(so it seemed), I exported/imported DHCP, synced DNS, and seized FSMO properly. I have looked through ADSIEDIT to see if there were any stale records of the old DC. There seems to be something funky with DNS and/or DHCP, as I am receiving event ID's 5781 NETLOGON, and 4013 DNS-Server-service, 1054 Group-Policy, and 10020 DHCP-Server warnings/errors.
These events are occuring when reboots are not even happening. Just all day long.
On Event ID 10020 DHCP-Server warning, I do not have iipv6 enabled on my NIC. All other NIC's disabled. ipconfig /all shows no ipv6 IP address.
Workstations are consistently and intermittently loosing connection to internet with Event ID 1014. This does not occur at the same time for workstations.
What I have done so far...

I have disabled all Windows software firewalls.
My DC points to itself as the DNS server.
DCDIAG reports no errors. (also with /test:DNS)
Have disabled slow link detection on workstation GPO and DC GPO.
Disabled autotuning.
Disabled task offload on DC
Created a _msdcs zone in the root of Forward lookup zones.

This is a solo DC. Solo DNS (active-directory integrated)
Forwarders point to my ISP which is Google. (8.8.8.8, 8.8.4.4)
I have not tried disabling recursion, as I don't really see that as a troubleshooting resolution for this problem.

After migrating the …
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I need to remove a domain controller from a subsite.
The subsite has a 10Mbit link to the main office. This link is and will be used by the organization to route users at this subsite through to the main office where the new domain controller is.

If I remove the server from the office here, and it hosts DHCP, DNS and AD, how can I simply redirect the users to the main office to login and authenticate through?

Will they find the domain controller automatically through the WAN link? Do I need to have something in place to point them there?
Any guides or docs would be much appreciated.
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Hi,
We have:
SCCM 2012 R2
DP in remote office with PXE options enabled (VM within HyperV)
DHCP is on a Cisco switch
Option 66/67 set on the switch, option 66 ip [address] & option 67 ascii smsboot\x64\wdsnbp.com

When we try to do a PXE boot it displays the following error: PXE-E32: TFTP open timeout, see screenshot attached.

We use to have DHCP on the physical server at the remote office and that was also the DP and this worked fine. Since moving the DP to a VM and the DHCP to the Cisco switch it is no longer working.

Thanks
IMG_20170614_122728--003-.jpg
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I recently concluded a successful domain migration from windows Server 2008 to Windows Server 2012 R2 Essentials.  The new server is acting as a DC and is operating well.

However I have a problem Adding roles and Features.  I tried installing the DHCP Role on 2012 in order to migrate DHCP from 2008 but I keep receiving the following Message:

"The Request to add or remove features on the specified server failed.  The operation cannot be completed because the server that you specified requires a restart""

It does not appear to matter which role or feature is selected   The result is the same and numerous restarts have not resolved the problem,  

Has any one come across this problem before and resolved it?  Many thanks
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Dear experts

Background:
- Softether VPN Server (Fixed public up say: located in Singapore)
- Using Dnsmasq for DHCP
- In Dnsmasq,
           dhcp-range x 2
           Interfaces x 2

Which dhcp-range will be used when VPN client connects to the VPN Server?

Is it possible for me to select dhcp-range when I initiate the connection from different country?
e.g. from Singapore                            --> Singapore, I am getting IP Range192.168.2.10-192.168.2.50
       from Country out of Singapore --> Singapore, I am getting IP Range 10.10.2.10-10.10.2.50

Any idea how I can achieve the above?
I appreciate you advises & ideas in advance.
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Server is domain controller in cloud, connected via VPN
Server is recently migrated - 2008 on premise to 2012 in cloud.

DHCP is running on local Cyberoam router
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Which VLAN   to enable ARP inspection

I would like to know which VLAN to enable ARP Inspection. Is it going to be on the same VLAN where the Trusted DHCP server resides on ?
Or on every VLAN in the network ?

Switch(config)#ip arp inspection vlan <VLAN Name>



I also wants to know about the DHCP Option 82 configuration.
Using IP helper-address <IP address> is enough or  we need to add:
ip dhcp relay information option

Thank you
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Hi All,
I have a Cisco 2600 router with 2 Ethernet and 1 serial interface, I have the fa0/0 connected directly to my internet modem(Comcast) and have the interface setup as a dhcp client to the modem. I have the fa0/1 interface connected to another cisco switch.
The fa0/1 interface is assigned a 192.168.1.1/24 ip and its also acting as a dhcp server to the internal hosts..
The Comcast modem IP is 192.168.100.1 which I had to get from Comcast.
I also have an ip route 0.0.0.0 0.0.0.0 192.168.100.1
I don't have any NAT running, not sure if I really need it or not my internal LAN is working fine, I can ping the gtwy, the clients are getting ips from the dhcp server..

I'm having the hardest time connecting to the internet, not sure what I'm missing, mind you I'm very new to the world of cisco networking so just experimenting in a lab environment and help would be greatly appreciated.

thanks..
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Good Morning!

What does the following two options actually do for DHCPd and does it work with failover?

allow booting;
allow bootp;


Im trying to configure DHCPd Failover and from what Im reading Im not quite sure if DHCP scopes that need PXE boot will work with DHCPd Failover. I believe the two options listed above would be needed but I dont know.  If so, should they be added in the primary and secondary dhcpd.conf files or the dhcpd.master?

Also the two options below -- are they also needed and should they be added in the primary and secondary dhcpd.conf files or the dhcpd.master too?

next-server x.x.x.x;
filename "xxx";

Thanks in advance!

Primary dhcpd.conf file
#authoritative;
ddns-update-style none;
ignore client-updates;
one-lease-per-client true;
omapi-port 7911;

#Failover peer section
failover peer "dhcp-partner" {
  primary;
  address server1.paychex.com;
  port 647;
  peer address server2.paychex.com;
  peer port 647;
  max-response-delay 60;
  max-unacked-updates 10;
  mclt 3600;
  split 153;
  load balance max seconds 3;
}
include "/etc/dhcp/dhcpd.master";

Open in new window


Secondary dhcpd.conf file
#authoritative;
ddns-update-style none;
ignore client-updates;
one-lease-per-client true;
omapi-port 7911;

#Failover peer section
failover peer "dhcp-partner" {
  secondary;
  address server2.paychex.com;
  port 647;
  peer address server1.paychex.com;
  peer port 647;
  max-response-delay 60;
  max-unacked-updates 10;
  load balance max seconds 3;
}
include "/etc/dhcp/dhcpd.master";

Open in new window


dhcpd.master file
option domain-name "example.com";
allow booting;
allow bootp;
next-server x.x.x.x;
filename "xxx";
option option-242 code 242 = string;

#dhcpd wants to listen on its own networks
subnet 17.8.4.0 netmask 255.255.252.0 {
  ignore unknown-clients;
}

#dhcpd wants to listen on its own network
subnet 19.4.8.0 netmask 255.255.252.0 {
  ignore unknown-clients;
}

#Scope [12.4.4.0] TEST PXE Boot
subnet 12.4.4.0 netmask 255.255.252.0 {
  option subnet-mask 255.255.252.0;
  option routers 12.4.4.1;
  option domain-name-servers 12.2.2.198;
  pool {
    failover peer "dhcp-partner";
    default-lease-time 300;
    max-lease-time 360;
    range 12.4.5.0 12.4.5.255;
  }
}

Open in new window

0

DHCP

9K

Solutions

4

Articles & Videos

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).