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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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after a journey abroad, we have returned to our offices to find our laptop can no longer connect to the local network or internet.

we get the yellow exclamation mark on the nic icon in the task bar.

i have tried several things like manually entering suitable ip details in the nic properties, resetting the ip stack with netsh, removing the nic drivers and re installing them, but nothing works.

i have tested the cables and all are error free.

the laptop fails to pick up any ip details if we use dhcp client, and we are just going round in circles.

can anyone assist in helping us resolve this?

windows v7 pro 64 bit is the os being used.

many thanks
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Hello all ,

   I have 2 DNS server in production and one DHCP server , which will lease the IP address to the Wireless clients. Unfortunately in LAN environment some one has wrongly entered the DHCP server address as a secondary DNS server address. By any chance , does it disrupt the network?

Thanks

Michel
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I am trying to implement some DHCP Reservations. It is on a SBS 2011 Server. When I look in the DHCP under Address Leases I see 172.18.2.132 BAD_ADDRESS with a description "This Address is ALready In Use".

   I am assuming it means the IP address is already in use? When I sort the leases there is only one 172.18.2.132 that shows up. How can I tell what other device is using 172.18.2.132? (if that is the problem)
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Hi I have 8 scopes on my DHCP server for my WiFi giving me 2016 address available but they keep filling up when i reconcile the scopes i get 4-900 bootp requests and when i delete them all is fine but it almost immediately starts to happen again. I have seen in other forums etc that PXE boot has caused this however as this is wireless this can not be the issue
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So I have an old sonicwall I am replacing with a fortigate.  The PC's have 7 day DHCP leases... The Fortigate will be set up to be the same IP as the sonicwall was and it will have the same DHCP range... But of course when I make the swap the fortigates lease list will be empty... Im curious - as PC's check in with the firewall, will they keep their addresses?  Or will they wind up getting reset the lowest available address at the time?

Any other concerns to think about with swapping the firewalls?  

Thanks!
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Hi everyone,
i have a lan network of 30 network equipment including printer and computer, and two wifi access point, i want a correct addressing plan knowing that i have no dhcp server, just the adsl router that does the dhcp work with an address range of 172.16.1.x / 24, some proposals for an addressing plan, thanks in advance
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Hi,

I have setup a Server 2016 VPN box, all is working, can connect and ping everything until.................

When I specify a different DHCP Subnet\Range (10.50.166.0/24 - VPN Client Range) I am unable to ping anything internally, if I change the settings BACK to the same subnet that the VPN Server is in all works. (10.50.10.0/24 - Server Range).

I'm guesing I am missing a route in RRAS?
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Hi Team,

We are currently going through a change of infrastructure and of service provider and I was looking for some advice on our situation.

The current network is provided as a "Lan Extension Service/Point 2 Point Layer 2" and goes through a second site:

Main Office -> Remote Office 1 -> Satellite Office 2

There are multiple subnets/VLANs within Satelite Office 2
Data VLANs within Office 2 are a mix of static and DHCP with IP helper pointing to remote end of LES (Main Office)

New provider is an MPLS solution
Remote Office 1 is being decomissioned

Is setting up a Site-to-site VPN from Main Office - Satellite Office 2 feasible with minimal impact? How could this be implemented successfully?

DHCP over IPSEC VPN (Cisco ASA's 5506) - will this work?
There is a plan for multiple S2S IPSEC VPNs for other services/sites

This is time critical and the transition should be seamless to the end users, however future change at Satellite Office 2 will see all clients go to DHCP.

Any advice or suggestions you can provide would be great!

Thanks!
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Currently running Server 2012 R2, need to extend on our subnet.  I've found several posts and docs on this, not many touch on adjustments for other devices or servers on the network.

Current IP subnet is 192.168.0.x

I'm looking at following this, will add 255 IP addresses:
https://devget.net/windows/how-to-increase-scope-change-netmask-in-windows-server-2012/

My static IP devices on the network, they will need to have 255.255.254.0 as their subnet mask, correct?  If they aren't updated, they just wouldn't see the second range of IP's at 192.168.1.x?

Routing shouldn't be an issue, correct?  The subnet makes sure the two IP ranges can see each other?

Our firewall IP is 192.168.0.1, any machines that get an IP in the 192.168.1.x subnet wouldn't have issues going out the 192.168.0.1 GW, correct?

Thanks!
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Hi
 I have a Windows 2012 domain with a  server that is the DHCP,DNS and DC. I cannot join the computers to the domain and l think the reason is that the when I  run the ipconfig/all the router  is shown as the DNS. The router DHCP has been disabled and all the workstations are getting their IP setting from the DHCP on the DC. I would appreciate your assistance
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Hi all,

I've successfully configured a clustered SRX220H2 on image 12.1X47-D30.4.

I've managed to get everything wokring, except for DHCP.

I think the issue is deeper, however, as even with a staticvally configured IP, my client cannnot ping the Juniper cluster, and vice versa.

I've gone as far as downgrading/upgrading and complete reset of the cluster, but cannnot find where I'm making a mistake.

FYI.... I have a legacy cluster (exact same set up - model, image, etc) and DHCP is working on that one. I've even taken the config, and uploaded this to the new one I'm setting up, without any success

Any assistance wiht this would be greatly appreciated.

Thanks
Jéan
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I have decided to use Linux unbuntu to setup a DNS server and read where masquerading with this is a good idea. Can anyone give me information where I can either use a VLAN and based on this setup a DHCP scope for that subnet. I have 4 subnets and would like to turn on DHCP for each of those subnets. It does not have to be by VLAN but wanted to way that each of my subnets can get an automatic IP and would like to consolidate this to one box that could also perform as a DNS forwarder to the internet from these 4 subnets.
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I'm researching a particular scenario and the feedback here is always great. I've hit a bit of a bump on this particular scenario and would love to get feedback from resident experts. The scenario is as follows:

There are 8 branches and random users at a single branch are unable to access internal applications or the Internet.

All other branches are working as expected and the majority of the users at the effected branch are working as expected.

·         Each Branch is connected with a 10MB connection to the Internet

·         Each Branch is using a /24 subnet

·         Each Branch is using DHCP

·         Each Branch has 90 employees (Laptop, Phone, Tablet)

What could be the problem? What steps do you take to identify the issue? How would you solve it short term?


My initial thought here is that the DHCP pool is exhausted, however, what little I know about subnetting indicates that only 254 hosts could join the network, but every other branch is comfortably supporting 270. Any thoughts on how to answer the three questions would be great.
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Hi, we have DHCP snooping enabled, and ASA doing DHCP-Relay. Between 2960-L and ASA is another switch doing snooping.

Anyway we have this 2960-L as access switch trunked at 4500. When not using dhcp snooping on access, all is working fine.
DHCP-Discover, DHCP-Offer from DHCP Server and PXE-Server, DHCP-Request from Client to PXE-Server for more information regarding PXE and the DHCP-ACK from PXE-Server with all the needed information(boot file name).

however when using ip dhcp snooping on 2960-L, the important last DHCP-ACK packets from the PXE-Server are not showing up at the client interface anymore. so the Client misses the PXE-boot important information for tftp, times out and does a DHCP-Release to restart the operation...

As i said, all is working fine with only disabling dhcp snooping on access switch.
IOS already changed from 15.2-5 to 15.2-6
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Not sure where to start with this one. I have a server running Server 2012 R2 that is virtualised on another Server 2012 box.

The virtual server is the DHCP server and of late has been dropping off after a few days and will come back online and issue addresses following a restart.

Not to sure where to begin on this as the service seems to be running etc even when it falls over.

Your help is appreciated!
0
Is it better to use DHCP on my hp proliant server (Windows server 2012 R2)  , or leave it to my router to control DHCP?  and If I use DHCP in my router, do I need to install DHCP rule in my server????

NOTE: I already configured my Routerboard951 with DHCP server, and there's already a defined  pool .
I'm going to create a client-server network with my own domain. I'm using hp proliant DL380P Gen8  with windows server 2012R2 installed.

thanks in advanced
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We recently installed a Windows 2016 Server which is to be a basic Domain Controller, File Server, and to be used for DHCP / DNS.

It was installed and working for a couple of days, until DHCP stopped giving out IP addresses.

The scope was configured to give out 150 addresses which is plenty for the amount of devices, and the lease time set to 24 hours.

The service was running fine, we restarted this. And the leases showed that there was still enough IPs to go round.

Checking event viewer we see the error shown in screen1 stating another program is using Port67.

I have checked the firewall and all the rules here for Port67 are DHCP related. We currently have the router giving out DHCP but this is causing issues, so any guidance on this would be great.

Any more info needed please let me know.
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Hi,

I need to setup static reservations for several devices on my LAN that connects to my Huawei B315 LTE Router via Wi-Fi. Under DHCP I do not see any option to reserve IP Addresses for specific MAC Addresses, is this possible to do with the Huawei B315?

Thanks,
Reinhard
DHCP-Options.JPG
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Hi

My predecessors had configured a subnet for  10.14.98.0/24 on the core switch with a separate VLAN and the VLAN ID is: 98. On the wireless controller I created new SSID called MARKT and also during the SSID configuration – under Advanced options – for the access VLAN , I have put 98.
Also I configure DHCP scope on the DHCP server and the address pool is (Start IP 10.14.98.2 – End IP :10.14.98.254)

The SSID (MARKT) gets broadcasted and when I click –connect- and after putting the wireless key and says ok. On the system tray - SSID the wireless icon I can see a yellow exclamation mark - it says Limited access.
Also if I hover the cursor on the wireless icon, it says domain. Local 2(unauthenticated)
No Network access.
If I do an ipconfig on the laptop it is releasing a different IP that belongs to a different SSID and subnet.
Please let me know how to troubleshoot this as where the problem could be . When do the ipconfig it must release the IP form this scope (10.14.98.2 – 10.14.98.254).
The Core switch is CISCO 3750  and the edge is WS-C2960X-48LPS-L.

This SSID is a new setup not sure if some configuration is missing .Any help will be great and thanks in advance.
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I have installed 'File Server' , through Wifi Enclosure device (Brand: Kimax). The Kimax DHCP router/enclosure creates shares folders that I can access through 'Network'  and I can do 'Map Network Drive'. I connect to Kimax router/enclosure through Wifi.

I have also internet modem + Router installed at my home say 'MyTel'. MyTel also creates hotspot/wifi.

I have connected Kimax with MyTel through LAN Cable. If I am connected with Kimax I can access file server plus I can surf internet.

Kimax assigns IP addesses as 192.168.169... whereas MyTel 192.168.10...

Now I want to access my file server from MyTel , which is host for internet access, I want to turn off Kimax hotspot/wifi.

Kimax supports DMZ, where I have to put an IP (I have no idea it should be Kimax serires or MyTel, I have tried both but failed)

I am non-IT guy trying to configure network, my knowledge of networking terms is limited to knowledge available on net.

Set-up:
'Internet Router - MyTel'  > 'File Server - Kimax' > LAN connections

Wanting:
'Internet Router - MyTel'  >  LAN connections (With access to File Server)


May be what I am trying to do is not meant to happen - but DMZ setting Kimax hints this can be done.  Please advise
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I would like to know  if it is  DHCP server that updates the DNS record for clients, or the clients themselves will update their DNS records in DNS Server.

For instance when DHCP server hands out an IP address to CLientX, would this client  update its DNS record on the DNS server or DHCP server would do it on behalf of the client ?

Thank you
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I had this question after viewing Repeating Event ID's 5152 and 5157.

Following up on techgrl89's comment - the resolution is incomplete.

Why on earth is the firewall logging normal DHCP and LLMNR broadcast/multicast traffic?  This question has come up for years and persisted across a number of Windows versions.  I've seen discussions on many websites and never seen a convincing answer.

If it were just the fact that the firewall is filling the security event log with stuff that doesn't realistically relate to security, I'd go with the auditpol solution.

But there are two complicating factors that keep the question coming back, year after year:
  1. Many people report that it happens on system A but not on identical system B on the same network
  2. Many people report that it's associated with normally open ports being blocked

I'm experiencing both of these.  Item 1 is disturbing because one would like security-related software to behave consistently.  I find it's inconsistent not only from host to host but on a single host over time.  I am lucky enough to be able to work around item 2, but I assume this is not an option for some people.  I've seen ports 1434 and 5985 spuriously blocked when all other indications on the system (the firewall rules listed in the firewall manager, winrm quickconfig, SQL Server config manager, etc.) say they should be open (within the designated scope).
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i have 5 vlans
vlan1
vlan10
vlan20
vlan30
vlan254
every time i try and connect wirelessly to any of these vlans it gives me a default ip address. seems to work if connected via cable though. seems last time this happened i had to restart a service in the dhcp server servers app.

anyone have any ideas
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Hello all,

I have one router working like a LNS with DSL. I have a vpdn-group with l2tp procotol and as source-ip a public IP.

Also, I have this virtual template.

interface Loopback0
 ip address 10.100.0.1 255.255.255.255   // in the real scenario this is a public IP
 
interface Virtual-Template1
 ip unnumbered Loopback0
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip tcp adjust-mss 1460
 peer default ip address pool Pool_1 Pool_2
 ppp max-bad-auth 10
 ppp mtu adaptive
 ppp mru match
 ppp authentication pap chap callin
 
 
ip local pool Pool_1 192.168.1.10 192.168.1.100       // In real scenario This is public IP range.
ip local pool Pool_2 172.26.1.100 172.26.1.200        // In real Scenario this is a public IP range.

Open in new window


I need to change this configuration to use cgnat and DHCP-pool instead local pool.

I created a DHCP in the router with the pool 100.64.0.0/16 (which is the ip range determined to use cgnat).
I tested the CGNAT with physical interfaces and it's working, but I need to do it with the vpdn and the virtual template so... my two questions are:

1) Should the virtual template be the ip nat inside and the vpdn the ip nat outside?

2) Using local pools with public IPs, I don´t have care about the loopback that is a public IP, but.. right now, if I use a DHCP-pool, Which is the gateway? In a regular dhcp configuration you use to make something like this:
ip dhcp pool internal pool
 network 100.64.0.0 255.255.0.0
 default-router 100.64.254.254

interface GigabitEthernet0/0/5
 ip address 100.64.254.254 255.255.0.0

Open in new window



So the physical interface is the one that has the gateway. But in the case using the virtual-template with the loopback with public ip, which one is the gateway?


Thanks.

BR
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Good Morning,

Could someone help me with a ISP fail over config on a cisco 1900 router please.

Interface one ---------- Outside --------------- 204.206.x.x
Interface two ---------- Inside ----------------- 192.168.x.x
Interface three-------- Backup ---------------- DHCP

When the 204 link is down the DHCP link pick up
0

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).