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19

With a very low lease time you will see an increase of network traffic, particularly broadcast traffic as the "discover" and "offer" phases of DHCP are layer 2 broadcasts. How much of an issue this is depends on many factors such as the size and complexity of the network, latency, performance of the DHCP server, etc. Keep in mind DHCP clients do not wait ...


12

Matching the DHCP lease times with the connection limit of your AP doesn't strike me as the best way of handling the issue. The two don't have to match. Lower the DHCP lease time to something like twice the length of the demo (completely arbitrary suggestion) and expand your DHCP scope to accommodate as many leases as you think you'll have in a reasonable ...


6

As MadHatter mentioned in a comment, the leases file is periodically re-created to avoid this problem. While the period isn't mentioned in the documentation, discussions on the dhcp-users mailinglist indicates that it should be done once an hour, and I've checked the source code and found that this is correct. Unfortunately this isn't a configurable option. ...


6

There's an official Technet guide for this that I'd use, rather than that one. The process below is a "merge," rather than what would normally be called an "import", and will only modify existing scopes if you import scopes that exist on the target server. If that is the case, you'll need to selectively import scopes, instead of just using the /all switch. ...


5

Set the value for option 51 to 4294967295 seconds and it will show up in the GUI as unlimited. C:\Users\EAnderson>netsh dhcp server scope 10.0.0.0 show optionvalue Changed the current scope context to 10.0.0.0 scope. Options for Scope 10.0.0.0: DHCP Standard Option : General Option Values: OptionId : 51 Option Value: ...


4

One thing that seems to be rarely suggested is inspecting at one of the clients that has a bad address and looking at where it came from. For example, on a Windows client "ipconfig /all" will tell you immediately what the rogue server address was. For long term monitoring, the check_dhcp plugin for Nagios can be set to warn if you have too many responses, ...


4

Here is the Technet DHCP Console Icon Reference Guide. That icon means: DHCP server warning. Available addresses for server scopes are 90 percent or more leased and in use. This means that the server is nearly depleted of available addresses to lease to clients.


4

It is possible, as outlined in this technet article. http://technet.microsoft.com/en-us/library/dn495425.aspx This guide describes the steps for migrating existing DHCP server settings to a server that is running Windows Server 2012 R2. Migration documentation and tools ease the migration of server role settings and data from an existing server to ...


4

Strictly speaking, yes. The client hardware address is a data field that will be in both the DHCPDISCOVER message (which won't leave the LAN) and the DHCPREQUEST message, which will be relayed by the relay agent. Why do you ask?


3

1 - Is there a limit to the number of DHCP Scopes I can deploy to a Windows Server 2012 R2 server? If there is, I'll need to consider adding more DHCP servers now. According to this: http://social.technet.microsoft.com/Forums/windowsserver/en-US/759becd0-9fbe-44e6-aac8-6f50036294c2/windows-2008-r2-x64-dhcp-server-maximum-scope-?forum=winserverNIS There is ...


3

This is not what search in resolv.conf does. It specified the DNS servers that your PC will use for DNS lookups, and the search domain used for hostname-only lookups. Example: nameserver 192.168.50.11 nameserver 192.168.50.12 search mynet.local In the above snippet, the servers 192.168.50.11 and 192.168.50.12 will be used for lookups, with the ...


3

The Windows DHCP server doesn't track anything about the "state" of a host to which it assigns an IP address. If the DHCP server receives DHCP requests from the same MAC address in two different subnets (presumably with one or both relayed through a DHCP relay agent) it will issue leases for that MAC in both subnets. (The same MAC address making multiple ...


3

The FORCERENEW provides the mechanism for the server to indicate to the client to re-new. Not sure if it is implemented in your distro.


3

If you have DHCP Audit logging enabled you might have the data in the logs. Details on how to set up DHCP Audit Log on Windows Server 2008 including the event types (e.g IP address lease etc) By default the log files would be located in %windir%\System32\Dhcp.


2

The configuration you're talking about is known as "split-scope," and the advantage it provides is redundancy - if one DHCP server goes down, the other can take over, instead of having your clients simply unable to receive a DHCP address. Of course, the reundancy comes with a management overhead, but it can be worthwhile. And since you're doing Windows, it ...


2

In what circumstances should you configure multiple DHCP servers on the same subnet? You want more than crappy uptime. My understanding of using more than one DHCP server is that your clients will use the nearest DHCP which could be unpredictable. This is probably why DHCP in Windows has the ability to work in a failover scenario with ...


2

Hopefully, you can control the hardware MAC addresses of your virtual ethernet interfaces. In that case, I had a similar problem, and ISC bind was equally uncooperating with my configuration efforts. The best solution, which I am still using for years reliably, is to edit the leases file so that desired IP addresses get assigned to corresponding hardware ...


2

You can't control somebody else's computer. If somebody else has "Administrator" or superuser-level access to the machine then all bets are off. You're better off doing this in the network, where you can control things. I see you say "...without the help of the router", but enforcing network policy with the network equipment gives you the best chance to a ...


2

Wireshark Try a running a protocol analyzer like Wireshark while connected to the subnet in question. You'll want to filter on bootp messages. If you want to do this in a truly passive manner, you'll have to wait until a client on that subnet initiates a DHCP request, after which you'll see all of the DHCP servers listening on the subnet respond to the ...


2

OK. So you want all of the traffic to go out the closest gateway, but you can't get there from here. It's all the same layer 2/3 network so there's no way to prioritize the gateways so that clients use the closest one. If you use different subnets on each side then that presents the wrinkle of having to route traffic between the two subnets so you'd then ...


2

As long as the routing is in place such that the DHCP relay to Router 0 actually traverses Router 2 & 1 to Router 0 and back, then yes, it will work just fine. It's no different than VLANs across Layer 3 switches with IP Forwarding enabled. You could even think of it as getting a DHCP address across a WAN link from a remote DHCP server if you'd like.


1

Try using the samba package. You may need to install libnss-windbind as well. This should enable using WINS as a name service. You will need to add wins to the hosts entry in /etc/nsswitch.conf. I have the bonjour package installed on a Window system, but its address is not available. Media services are announce, but only have the machine name. ...


1

First of all you have to use a managed switch. If you are not using a managed switch, then nothing is stopping a person with sufficient privileges on individual machines from simply spoofing a MAC address of another machine. Once the MAC address is being spoofed, there is no way to tell the difference between the two. With a managed switch you can either ...


1

No, this will not work. Both DHCP Servers must be at least Windows Server 2012. As an aside, you should be removing 2003 from your environment quickly, not tying it in to new infrastructure. It goes end of extended support early next year.


1

Assuming Windows: Run Wireshark. Do ipconfig /release followed by ipconfig /renew on the command line.


1

You need a BOOTP and TFTP server. You could set "next-server" to your current DHCP server setting to your TFTP server too. You won't be able to run remote boot without correct BOOTP server set to TFTP server (next-server). First you need a BOOTP/DHCP server to setup the client network configuration and inform what server will be used for PXE/TFTP server. ...


1

I am 95% sure the DHCP server in Cisco IOS doesn't record this information at all. You'll need to run your DHCP server somewhere else, or collect the hostnames through some other mechanism.


1

I hate to post and then immediately post my own answer but when I was working on getting the DHCP client configuration and leases file I noticed about half a dozen lease entries. Just to create a clean file to post here I deleted that file and rebooted. After that it grabbed the proper DNS server info. While I feel there was more to it my solution was to ...


1

There is probably no reason to keep it like this, it's unnecessarily complicated. 192.168.50.0/24 and 192.168.51.0/24 can be combined into one subnet, 192.168.50.0/23, so you could reconfigure that on the DHCP server and get rid of the Superscope. Then configure it as 192.168.50.0/23 on the router/vlan as well. The only issue is going to be subnet mask ...


1

Each server will log to it's own Event log upon running out of ip addresses in it's portion of the scope. Create a Task on each server to send an email for that Event.



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