DHCP scope setings from multiple DHCP Servers
Is there any way to check any particular option is configured in all scopes from multiple DHCp servers.
for eg:- we would like to check if any scope has option 150 is configured in multiple DHCP servers.
I guess there are lots of cmdlets available from Win2k12 DHCP servers.
Regards, Nidhin.CK
Hi, Nidhin...
I use NETSH tool for this, can redirect results to file or filter w/ FIND.
Example:
NETSH dhcpserver \\SERVERNAME dump | FIND /I "set optionvalue 150"
Hope this helps!
Marcelo Lucas Guimarães - MCP, MCTS, MCDBA, MCITP Blog: http://mlucasg.wordpress.com
Similar Messages
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how a dhcp client select a offer among offer from multiple dhcp server
Pankaj
It usually just accepts the first one. So if you have 2 ip helper-addresses under the vlan interface DHCP requests are sent to both DHCP server. Generally speaking the DHCP servers that replies first is the one used.
Jon -
Running a Select query against multiple sql servers using SSIS script task.
Hi Guys,
I need to fetch data from multiple sql servers using SSIS scirpt task inside a foreach container.
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Thanks in advance.Your only options is using .net code, then it will be no different than using a console app in a loop.
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Arthur My Blog -
Application Server slowdown with multiple proxy servers ?
Our environment has our iAS boxes talking to iWS web servers which are front-ended with iPlanet Proxy servers (Proxy 3.53 I believe). We are seeing significant slowdown if we try and hit our web apps through the proxy as opposed to going directly to the web server (bypassing the proxy servers). One of our "proxy" guys recalls hearing that there is an issue with the app server's handling of sessions if requests from the same user come in to the web server (and by extension the app server) from multiple proxy servers with different ip's. Has any body ever encountered this or does any body know if the app server has an issue handling the same sessions whose requests come from different ip addresses (different proxies)?
The proxy work with HTTP 1.0 and the webserver with HTTP 1.1.
This difference could be the cause of your problems.
"David Fuelling" <[email protected]> escribio en el mensaje
news:[email protected]..
Our environment has our iAS boxes talking to iWS web servers which are
front-ended with iPlanet Proxy servers (Proxy 3.53 I believe). We
are seeing significant slowdown if we try and hit our web apps through
the proxy as opposed to going directly to the web server (bypassing
the proxy servers). One of our "proxy" guys recalls hearing that
there is an issue with the app server's handling of sessions if
requests from the same user come in to the web server (and by
extension the app server) from multiple proxy servers with different
ip's. Has any body ever encountered this or does any body know if the
app server has an issue handling the same sessions whose requests come
from different ip addresses (different proxies)?
Try our New Web Based Forum at http://softwareforum.sun.com
Includes Access to our Product Knowledge Base! -
Multiple Lease Duration for one DHCP Scope?
Hi All,
I have an urgent question. I wanted to know if it is possible to have many lease durations for different computer groups getting their addresses from one DHCP scope. I saw somewhere that it is possible to use User Classs or Vendor Classes for setting a lease
duration for a group of computers sharing the same class Id ?
If it is true, How can to configure ?
Also i would like to know about the lease duration period what is the maximum days can we have ( 8 days After )?
Thanks
AtulPlease refer to the following-
http://social.technet.microsoft.com/Forums/windowsserver/en-US/26de79f9-6ad7-4088-9077-006b9dd8c1fb/multiple-lease-durations-for-one-dhcp-scope?forum=winserveripamdhcpdns
You can configure any value as lease duration; however if you want a very big/infinite value; it makes sense to convert the lease(s) to a reservation. -
NetBoot and Multiple DHCP Servers
Hey everyone,
We have a NetBoot machine running here at my school (where I work). It was working like a champ until a couple of weeks ago when our network got upgraded and there are now 2 DHCP servers on our network. That, for some reason, is totally screwing up our NetBooting process.
Here's what I think is happening, and maybe someone can tell me if I right or wrong. NetBoot (or BSDP protocol) is a "broadcast" protocol. (That means it's always just floating around out there on the network. ) NetBoot (BSDP) protocol gets injected into the DHCP stream, and any machine that gets DHCP can get BSDP, and essentially NetBoot.
The problem is with BSDP. BSDP protocol wants to have all of it's "broadcasts" come from the same server. So when we had 1 DHCP server, everything was fine, because client machines would get their whole NetBoot process from one machine... all of the BSDP broadcasts were coming from our 1 DHCP server.
Now, we have 2 DHCP servers. What happens is, a client will get some of it's BSDP broadcasts from one DHCP server, and some from another... which it does not like at all.
I recently read somewhere that it is possible to somehow make one of our DHCP servers the "authoritative" server, to which all of the clients will go to get their NetBooting info.
Does this sound in any way right? Are we on the right track ? Has anyone seen this before? Any help would be greatly appreciated. Thanks a million.
MikeNow, we have 2 DHCP servers. What happens is, a
a client will get some of it's BSDP broadcasts from
one DHCP server, and some from another... which it
does not like at all.
Not unless your new DHCP server is also a NetBoot server and is set to provide NetBoot services. BSDP and DHCP are not the same thing. If what you were saying were true, it wouldn't be possible to have DHCP and NetBoot offered by different servers.
It IS possible, however, that the two DHCP servers are causing problems by both servicing DHCP requests for the same clients. If you've got multiple DHCP servers on the same subnet (or your router's configured to pass DHCP requests between subnets), you should make sure that only one of the DHCP servers answers requests from any given client. In our world, our Novell server is the default DHCP server on our subnet, but I keep a list of excluded MAC addresses on that server so that my Macintosh clients don't get addresses from it. On the Mac OS X server, I'm careful to limit my address ranges only to those machines which have static address maps in NetInfo. That way, our servers coexist, but they don't overlap.
It's not clear from your message whether your previously solitary DHCP server was your Mac OS X server, or whether one of the two DHCP servers is that box. But whatever the servers are, it might be helpful to turn off one of them to see if the same problem occurs (assuming you can, without major network disruptions). If that's not possible, can you talk to your network admins to see if there's some way to isolate your clients and one of the servers--in other words, see if there's some way to keep DHCP servers from responding to the same requests.
There may be any number of other reasons why this problem has cropped up. You may need to dust off a hub and a copy of Ethereal or EtherPeek to sniff what's happening on the network. You might also try NetBooting in verbose mode, to see where the process craps out. IIRC, there'a decent guide for this kind of troubleshooting over at Bombich's site (www.bombich.com).
Good luck.
David Walton -
WLC 5508 and Multiple DHCP servers in different sites?
Hi
I work for health authority in our region and we just purchased a Cisco wlc 5508 controller along with 25 3500 AP's. We have multiple sites with different IP subnets in each, all connected by a frame relay (owned by ISP). Each site has its own DHCP server. I have the controller in our main site. So when I take an AP to a remote site, the Ap gets an DHCP address from local DHCP server (which is great) and contacts controller and joins controller. Everything is good. BUT, when a client joins at the remote site, it gets an address from a previous site which will not work because the client is now on a different subnet. We dont use Vlans as they dont transvers the frame relay. I need those clients to obtain DHCP from the local DHCP server from the site they are on. Is that possible??
I have updated the controller to latest version as well.
Thanks
Bryan Yaciuk, CCNA
Parkland Regional Health AuthorityWe call this as HREAP LOCAL SWITCHING!! but here is the catch.. everytime the AP joins the new site.. we need to configure the VLAN mapping and this wil do it for you!! Here is the link which will resolve ur issue..
http://www.cisco.com/en/US/tech/tk722/tk809/technologies_configuration_example09186a00807cc3b8.shtml#ll
Lemme know if this answered ur question and please dont forget to rate the usefull posts!!
Regards
Surendra -
Multiple DHCP scopes on WLC 5508 (not showing leases?)
I have 2 DHCP scopes set up on a wlc 5508, one for the AP's and another for a wlan, the leases for the AP's scope show up, but the one that the clients on the WLAN are on do not show up in the "show leases" is that a bug? normal?
Customers using Cisco Unified Wireless solutions have been reporting issues with the DHCP support provided on the Wireless LAN Controller (WLC). Some of these issues are software bugs or debugability problems. Others are due to lack of proper understanding on the DHCP implementation.
This document describes the different DHCP operations on the wireless controller, which provides consistent and accurate information to customers in an effort to reduce the related customer issues and TAC cases.
Please refer to the following link: http://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/110865-dhcp-wlc.html -
DHCP Scopes and Scope Options Import & Export
I need to adjust lease times for over one hundred scopes spread across multiple servers (about half of them are on one server, though). There will be 2 or 3 different lease times used. What is the best way to do this?
I know I can use netsh to change the option for each scope. But I would like to script the collection of the list of scopes, rather than typing the list manually. Is there a way to export a list that contains just scopes and descriptions?
ThanksHi,
Actually, it can be exported as txt file.
netsh dhcp server export c:\DHCP\myscopes.txt
Export-DhcpServer
And you can also manage it via powershell
Use the PowerShell DHCP Module to Simplify DHCP Management
http://blogs.technet.com/b/heyscriptingguy/archive/2011/02/14/use-the-powershell-dhcp-module-to-simplify-dhcp-management.aspx
Hope this helps. -
Ip source guard feature and dhcp DHCP scope exhaustion (client spoofs other clients)
Hi everybody.
A dhcp server assigns ip adress based on mac address carried by client hardware field in dhcp packets.
One potential attack is when a rogue host mimics different mac addresses and causes dhcp server to assign the ip addresses until no ip address is left for legitimate host.
For e.g a host h1 with mac1 has assigned ip address by dhcp server as:
199.199.199.1 mac1
Dhcp server has the above entry in its database.
Using hacking tools such as Yersinia or Gobbler one can create a dhcp discover messages each time creating a different mac for client hardware field in dhcp server thereby causing a dhcp server to assign ip addresses because to dhcp server , these are legitimate dhcp discover messages with each carrying a different mac in client hardware addresses.
You might say use dhcp snooping and it will prevent that ( dhcp scope exhaustion) and configure the switch to check if src mac matches the client hardware address in dhcp message. But still we can creat spoofed discover messages where src mac in ethernet header will match the client hardware address in dhcp discover message. We still did not overcome the problem.
You might say use IP source guard feature but will it really prevent that problem from happening?
Let me illustrate it :
h1---------f1/1SW---------DHCP server
Let say we have configured dhcp snooping on sw1 and f1/1 is untrusted port. The switch has following dhcp binding
199.199.199.1 mac1 vlan1 f1/1
Next we configure ip source guard to validate both src mac and src ip against the dhcp bindings . When we configures ip source guard first , it will allow dhcp communication only so a host can request ip address and a dhcp binding can be built. After that ip source guard will validate src ip or src mac or both against the dhcp binding.depending upon how we configure ip source guard.
In our case we have configured ip source guard to validate both src mac and src ip against the dhcp binding.
A dhcp binding is already created as:
199.199.199.1 mac1 vlan 1 f1/1
Now using the hacking tools Yersinia or Gobbler on h1, we create our first spoofed dhcp discover message where src mac=mac2 in ethernet header and client harware address= mac2 in dhcp discover message. Since switch is configured with ip source guard feature and therefore allows dhcp discover message to pass through. Dhcp server upon receiving the dhcp message assigns another ip address from the pool. Now the dhcp server has following entries:
199.199.199.1 mac1
199.199.199.2 mac2.
We can continue to craft spoofed dhcp discover messages as mentioned above and have dhcp server keep assigning ip addresses until the whole pool is exhausted.
So my question is how does ip source guard in conjuction with dhcp snooping prevent this particular attack from happening? ( i.e DHCP scope exhaustion)
I really appreciate your input.
thanks and have a great week.Thanks Karthikeyan.
First of all, we gather all the information about the locations of legitimate dhcp servers in our network. Once we have this information, we will configure the ports used to reach them as trusted. All the ports where end users will connect will be untrusted and therefore subject to dhcp snooping .
it means if any of user connected in that switch/vlan runs a dhcp services like vmware for eg. Snooping will prevent the dhcp/bootp servers connected to that port will not be able to process.
Yes that is correct. Because dhcp snooping feature will check these ports for the messages usually sent by dhcp server such as dhcp offer, etc. If the end user is running dhcp server using virtual machine, that port should be configured as trusted if it is dertermined that end user is running a legitimate dhcp server using vm ware.
When we have the dhcp snooping it prevents the 1st level of hacking itself. I don't think so it will have any impact on dhcp address releasing.
I am sorry. You lost me here. What is 1 level of hacking?
Dhcp snooping checks for dhcp messages such as dhcp release, dhcp decline.on untrusted port against the dhcp bindings.
Here is why;
h1---------SW1-------dhcp server
|
h2
Let say we don't have dhcp snooping in above attack and h2 is a legitimate user has already assigned ip address 199.199.199.2 by dhcp server. Thus the dhcp server has an entry:
199.199.199.2 mac2
Next we connect rogue user and it gets ip address 199.199.199.1 now the dhcp server has entries:
199.199.199. 1 mac1
199.199.199.2 mac2
Now using hacking tools, h1 create a fake dhcp release message with 199.199.199.199.2 mac2
Dhcp server upon receiving this message, will release the ip address and returns it to the pool.
By using DHCP snooping, switch will peer inside dhcp release message and checks against the binding. If there is conflict, it will drop the message.
IFor e.g
If have dhcp snooping configured , then switch will have adhcp binding as:
199.199.199.1 mac1 vlan 1 f1/1 lease time
199.199.199.2 mac2 vlan 2 f1/2 lease time.
If h1 tries to send fake dhcp release with ip address 199.199.199.2 mac2
Switch will check ip address 199.199.199.2 and mac2 against the binding related to f1/1 . Sw will find a conflict and therefore drops the dhcp release packet.
Thanks -
How to check whether DHCP scope is fully leased/ exhausted on CUCM Publisher?
Hi All,
we have few new 7942 phones deployed and they are not registering.
we suspect that dhcp scope configured on cucm pub do not have any free ips to assign.
we need to know a way to confirm DHCP indeed is the issue.
Any suggestions will be very helpful.
Thank youHi,
I do not have any customers who run DHCP on CUCM servers but I would suggest that you look at using RTMT to collect log files from the DHCPMON service.
You could also check out the blog below:
http://bhatkoti.com/2009/02/16/how-to-check-call-manager-6x-5x-7x-dhcp-lease/
The solution proposed is kind of neat but may not be something that you would be comfortable with.
Hope this helps -
When editing DHCP Scope in IPAM, get "Error: 5 - Access is denied"
Hello all!
I have a pair of Server 2012 DHCP servers configured for Failover. I also have a Server 2012 IPAM server that manages the first server in that pair, but not the second one. The reason is that I have the DHCP Failover Auto Config Sync tool running
on the first server and it can only be installed on one server of a Failover pair.
So, my diagram would look something like this:
IPAM --manages--> DHCP 1 <--Failover/Auto Sync--> DHCP 2
So, here is my problem. I can make a change to a DHCP Scope directly on DHCP 1 and it is instantaneously replicated to DHCP 2. That is no problem.
But, when I try to edit the same Scope through IPAM, it fails and returns the following error: (Error:5 - Access is denied.)
Any help would be greatly appreciated.
Thanks!Hi,
One of our service engineers here was able to reproduce the problem by removing the
IPAM computer account from the IPAMUG security group in Active Directory.
Interestingly, doing this does not change the status of the server from green to red in terms of manageability.
Can you please check and see if this is the problem?
Thanks,
-Greg
P.S. If this is not the problem, please answer a few more questions:
Is the IPAM and DHCP server joined to the same domain?
Are they multihomed servers or have only one NIC?
Are you using the same user account on IPAM and DHCP server?
Note: I tried reproducing this and when the IPAM server is removed from the IPAMUG group it does cause Error 5 - Access is denied, however I was able to get the status to turn red after doing this. I think it is critical that an Active Directory update
occur, so you should try running gpupdate /force on your DC, DHCP server, and IPAM server. -
Multiple DHCP on Multiple VLAN not working
Hi there;
In my core network switch, I have multiple VLANs, I have these command to assign to DHCP pools. I configured a port on my core switch for DMZ_VLAN and when I connect my computer to this port, I can get the ip address from the dmz_vlan dhcp pool. Because I assigned an IP address to the interface of vlan 192, then I found that one of my server "192.168.0.100" connection dropped, I cannot ping this server on the dmz VLAN, and it cannot provide the http service as usual until I remove the "interface vlan 192" from the switch. Why? However; without this command, I cannot receive the 192.168.0.0 network IP from the pool.
ip dhcp pool data_vlan1
network 10.10.1.0 255.255.255.0
default-router 10.10.1.1
dns-server 10.10.1.100 10.10.1.101
domain-name company.local
lease 7
ip dhcp pool dmz_vlan
network 192.168.0.0 255.255.255.0
default-router 192.168.0.1
dns-server 8.8.8.8 4.2.2.2
domain-name company.com
lease 7
interface vlan 10
ip address 10.10.1.254
interface vlan 192
ip address 192.168.0.254Sorry for the delay as I got busy with work. If your layer 3 switch is the default gateway for VLAN 192 then the default-router for the DHCP scope should be the IP address of the layer 3 switch interface (192.168.0.254). With that being said, the FW DMZ_192 interface, the switch SVI for VLAN 192 and the DMZ server should all be in the same broadcast domain, thus they should be able to reach each other.
So, can you confirm with me exactly what does not work on the server configured with VLAN 192 and a static IP? For instance,
1. Can you ping the server from the L3 switch
2. Can you ping the server from the FW
3. Can the server ping 192.168.0.1 and 192.168.0.254
4. Can the server ping the outside world? For instance, www.google.com and 4.2.2.2
5. Have you tried taking a test PC, connecting to the switchport configured for VLAN 192 and see if you get an IP address from the DHCP scope -
ASA Migration of DHCP Scope to a Server
Hello All,
We migrated the DHCP scope from the ASA to a MS DHCP server with this configuration:
group-policy BV-SSL1 internal
group-policy BV-SSL1 attributes
no address-pools value remotepool4 remotepool2 remotepool3
no intercept-dhcp enable
dhcp-network-scope 10.180.49.0
exit
tunnel-group BVVPN10 general-attributes
no address-pool remotepool2
no address-pool remotepool3
no address-pool remotepool4
dhcp-server 10.182.14.55
exit
tunnel-group BV-SSL general-attributes
no address-pool remotepool2
no address-pool remotepool3
no address-pool remotepool4
dhcp-server 10.182.14.55
exit
no vpn-addr-assign aaa
no vpn-addr-assign local
vpn-addr-assign dhcp
This is running good, until we used all 254 addresses that was specified in the dhcp-network-scope.
My question is should i have specified dhcp-network-scope none to allow for all 3 scopes can be used to hand out IP addresses for the remote users?
Thanks,
KimberlyOkay, that's at least a good start. Can you monitor the ULS logs while you attempt to browse to the site to see what form of error(s) you're getting?
Trevor Seward
Follow or contact me at...
  
This post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs. -
I'm migrating from a Windows 2003 server running DHCP to a Windows 2012 server with DHCP. I would like to do the migration by moving a single scope at a time. I'm only finding ways to move the entire scope. Can you move a single
scope at a time? I really appreciate any help.Hi
on server 2003
- cmd console "netsh dhcp server export c:\dhcpbackup.txt all
->enter
- stop dhcp serivce and set start up type "disabled"
copy "dhcpbackup.txt" file from 2003 to 2012 (on c drive or etc)
- install DHCP role on server 2012 but do not configure or create any scope.
- also check for is there any scope on 2012 "netsh dhcp server Show scope" if there is any "netsh dhcp server delete scope(ip of scope) dhcpfullforce" to delete
- "netsh dhcp server import c:\dhcpbackup.txt all" (where the backup file avaible)
- finaly server manager->Tools- Open "DHCP" check the situation (if there is a red cross on,right click on dhcp server click "authorize" and "Activate" .
Or you can use migration tool also;
https://technet.microsoft.com/en-us/library/dd365353%28WS.10%29.aspx?f=255&MSPPError=2147217396
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