New VLan can't talk to DHCP server

We have just created a new vlan (172.18.1.0/24 vlan 3) on our network and we are trying to use an exsisting DHCP server (192.168.0.1 vlan 8) But the clients on the 172.18.1.0 network can't connect to this DHCP server on vlan 8. My questions are.
1. Do we need to specify vlan 3 on the switchport that the DHCP server is plugged into?
2. Is there something @ L3 we need to enable to pass these DHCP server messages too across these vlans?
Has any used DHCP servers on different subnets?
Any info would be great.

You need to configure an IP helper on the appropriate VLAN interface(s). Routers, by default, will not forward broadcast packets. Since DHCP client messages use the destination IP address of 255.255.255.255 (all Nets Broadcast), DHCP clients will not be able to send requests to a DHCP server on a different subnet unless the DHCP/BootP Relay Agent is configured on the router. The DHCP/BootP Relay Agent will forward DHCP requests on behalf of a DHCP client to the DHCP server. The DHCP/BootP Relay Agent will append its own IP address to the source IP address of the DHCP frames going to the DHCP server. This allows the DHCP server to respond via unicast to the DHCP/BootP Relay Agent. The DHCP/BootP Relay Agent will also populate the Gateway IP address field with the IP address of the interface on which the DHCP message is received from the client. The DHCP server uses the Gateway ip address field to determine the subnet from which the DHCPDISCOVER, DHCPREQUEST, or DHCPINFORM message originates.
See more at the following document, with configuration steps and examples:
http://www.cisco.com/warp/public/473/100.html#configdhcpbootpciscoios

Similar Messages

New client cant get ip from dhcp server (web authentication)

We have WLC 5508 with two SSID staff (vlan 58, PSK auth) and customer (vlan 48, web auth)
Recently, new client can connect to SSID staff without problem but It cant get IP when it connect to Customer SSID.
many other client ( smart phone, laptop) which connect for few week still connect to Customer normally.
DHCP server still have a lot of IP for wireless client.
We want to use firewall to make policy for Customer so we put gateway of vlan 48 on the firewall.
Please check the dubug client file.
Thanks.

The debug just shows a single DHCP Discover attempt when attaching to WLAN with VLAN 48 interface. It appears the client is simply not pulling an IP (not the WLCs responsibility), although you are using DHCP-Proxy.
Can you put a wired client in VLAN 48 on the same switch as the WLC and have a client pull an IP?

Wired ethernet can't communicate with DHCP server

Hi all
I have a Mac Mini running Mac OS X Server. I recently changed a bunch of network settings, and since then I can't get the Mac to acquire an address from DHCP through the wired connection.
The wireless ethernet connects to the same router and acquires it's IP address, DNS, and router information through DHCP without a problem.
The wired ethernet connection is unable to communicate with the DHCP server. The router detects it, and sees it as having it's self-assigned ip address (169.254.74.247). The subnet mask is wrong (255.255.0.0 vs. 255.255.255.0) as well. Both are greyed out in network preferences when DHCP is selected. I've tried all of the obvious steps (restarting networking, rebooting everything, running the diagnostic tool, disabling wireless airport, etc.) to get it to work, with no change.
I can get it to connect with a manually assigned IP, but that's not a long term solution for my network.
I have had this issue with multiple routers. Currently I'm using a gigabit-e router - netgear WNDR3700. Other machines connect to the router just fine through wired ethernet (xbox360 and linkstation mini).
I'm new to Mac OS, but not new to networking. Any help would be appreciated.

This might be an old discussion but it was helpful to me. Well, almost. After reading this discussion, I arrived the same place that xoofoo above did. After some poking around, I was able to find the answers. (Feel free to correct me if I'm wrong, please!)
Here's what I did:
Launch "Server Admin" in Applications/Server folder
Open the list of services by clicking on the triangle next to the Server listed in the left pane.
Click on "Firewall"
Click on "Settings" tab
Click on "Editing services for" and select "192.168-net" (or if necessary, select "any".)
In the window below, go down the list and tick both "DHCP and Netboot client" and "DHCPDISCOVER". (hint, this list is sorted by ports number, go down and look for port 68).
Click "Save".
That should do the trick! Hope this is helpful to others in the future.

Two SSIDs; different VLANs; second VLAN can't talk to Internet

I've got an ASA 5505 firewall with internal interface 192.168.65.1 on port 1 and a WAP connected to port 5 with the address 10.10.1.1. The WAP has two SSIDs configured; one is on VLAN 1 and the other on VLAN 14. The firewall has port 5 configured as a trunk for VLAN 1,14 and the interface was configured a VLAN 14.
If I connect to the WAP using the SSID on VLAN 1 I get an address of 192.168.x.x from our internal DHCP server and have full connectivity to the internal and external networks. If I connect to the SSID on VLAN 14 I get an address of 10.10.1.x from the firewall DHCP server but am unable to connect to anything.
When connecting to the SSID on VLAN 14 I want to be able to access the external interface but not anything internally. I have configured a firewall access rule to allow 10.10.1.0/24 to outside and deny 10.10.1.0/24 to 192.168.0.0/16 but this hasn't worked.
Any ideas?

You need to configure an IP helper on the appropriate VLAN interface(s). Routers, by default, will not forward broadcast packets. Since DHCP client messages use the destination IP address of 255.255.255.255 (all Nets Broadcast), DHCP clients will not be able to send requests to a DHCP server on a different subnet unless the DHCP/BootP Relay Agent is configured on the router. The DHCP/BootP Relay Agent will forward DHCP requests on behalf of a DHCP client to the DHCP server. The DHCP/BootP Relay Agent will append its own IP address to the source IP address of the DHCP frames going to the DHCP server. This allows the DHCP server to respond via unicast to the DHCP/BootP Relay Agent. The DHCP/BootP Relay Agent will also populate the Gateway IP address field with the IP address of the interface on which the DHCP message is received from the client. The DHCP server uses the Gateway ip address field to determine the subnet from which the DHCPDISCOVER, DHCPREQUEST, or DHCPINFORM message originates.
See more at the following document, with configuration steps and examples:
http://www.cisco.com/warp/public/473/100.html#configdhcpbootpciscoios

Blu-ray can't communicate with DHCP server since I upgraded to Lion

Hi gang, hope someone can help me out. I have a Sony Blu-Ray DVD BDP-N460 that I normally use to connect to the internet and watch streaming Netflix, etc. with no problems, until I upgraded to Lion. Now, for some reason, I get an error message: "Having trouble communicating with the DHCP server." I use a wired connection directly to my AirPort Extreme, and I also use a Motorola SBV5220 SURFboard Cable Modem. I haven't changed my internet servings on my Mac.
Under system settings on my Blu-Ray on-screen display, it says "Physical connection OK, Local Settings OK, Internet Connection Failed." I've tried umpteen times going through the automated setup on my Blu-Ray, where the system automatically detects settings, etc...everything I did when I first set the system up. And I've tried countless manual setting combinations. No luck. This is really weird because I had no problems in the past...the culprit seems to be Lion because this glitch happened simultaneously with my upgrade.
I am not a networking expert so any help will be greatly appreciated.
I'm running Lion 10.7.1 on an iMac 2.4 GHz Intel Core 2 Duo with 2GB 667 MHz DDR2 SDRAM.
Thanks.

Update: So here's what's happened. I figured I would ditch the Sony and get a $99 Apple TV. I still had the same connection issues.
(FYI my network is now set up like this: Motorola Cable Modem via Ethernet to Time Capsule via Ethernet to Mac. In a separate studio, Airport Extreme wirelessly connects to Time Capsule; Airport Express connects to Extreme via Ethernet cable. For this discussion, only Time Capsule applies, not Extreme as mentioned above.)
I called support, and they had me read my Time Capsule's IP Address, Subnet Mask, Router, and DNS Server numbers to them. Then, they had me manually input those numbers into my Apple TV (via my TV screen), number-for-number, EXCEPT they had me increase the last digit of the IP Address by one (for example, my Time Capsule's IP was 10.0.1.2, and they had me make my Apple TV's IP Address 10.0.1.3).
I assume these settings would work on the Sony DVD. I'm so happy with the Apple TV that I don't even want to go back and try.
Sorry, Apple, for blaming the whole thing on Lion. Not really sure why all this happened out of the blue though.
Hope this helps somebody. I'm a happy camper now. Apple TV rocks.

New MacBook can't add OS X Server in Directory Utility

The first time I try it, I get a error -14071 (eDSInvalidReference). On the second try, I get -14740 (eServerSendError).
The only other workstation I have handy is a 10.4.11 iBook from which I can happily remove and recreate the binding.
Am I stuck on the bleeding edge? Has anyone gotten these new machines bound?
EDIT: During these attempts, Directory Service is indeed crashing. This is a COMPLETELY virgin MacBook.
Message was edited by: jaydisc

Are you attempting to connect to the OD via SSL. 10.4 clients will connect via SSL, but 10.5 client's by default won't. See http://www.afp548.com/article.php?story=20071203011158936 "SSL and LDAP in Leopard" about the differences and how to connect 10.5 via SSL.

AP gets always a new IP address from DHCP server

Hello,
When an access points doesn't find a controller it gets always a new IP address from DHCP server.
Does anyone know, why?
thanks

Hi,
From what I know this is to do with DHCP option 60 and 43.Normally when APs request for IP address, DHCP Server also returns the management IP Address of WLC if the VCI matches.
If the VCI sent by the AP does not match with the one configured under DHCP for that particulart AP type, the DHCP will never return the WLC IP and hence AP can not find the controller.And the AP keeps sending DHCP Req and sometimes end up getting two IP addresses!
So may be you can check VCI on DHCP server for that AP model.
Let me know.
Cheers

Light weight AP cannot Get IP from windows DHCP server

Hi all :
We user WISM ver.5.0.148.2 , All AP is 1230 Series and Use Windows 2003 DHCP server.All AP cannot get IP after upgraded Lightweight from Autonomous IOS.
But I found the DHCP is work if i use my notebook connect the same switch port and my notebook can get IP from DHCP server.
Anyone can tell me why MY Lightweight AP cannot get IP from DHCP server ???
thx any idea .
I confirm the AP DHCP setting enabled and the config as below :
AP000d.bc41.4392#show ip inter bri
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES DHCP up up

hi fella5:
yes , it's done , the WLC already have the SSC Code and i verify the SCC code is correctly.
the Switchport configured that vlan 99 access port and the Global Vlan ID set the IP helper to the DHCP already.I can ping to the DHCP , DNS and WLC.

How to replace DHCP server from domainA with DHCP from domainB?

Hello fellow Administrators,
We have one remote site with one subnet. There's domainA domain controller and about 100 domainA's client computers in that subnet. We're about to send 100 domainB's client computers there as well.
There's also domainA's DHCP server running on the same subnet. DHCP scope options include domainA's domain name, gw and domainA's DNS server addresses.
DomainA and DomainB belongs to separate forests and there's two-way trust between them. DomainA DNS has stubzone for DomainB and DomainB has stubzone for domainA. That's how
clients can resolve hostnames of other domain.
All domainA's clients in remote site will be replaced gradually with domainB's client computers, but this can take a long time.
I want to note, that I cannot create second subnet for domainB at the moment.
At some point, we need to deploy DHCP server to domainB's member server in the remote site. What are the steps I should take to replace existing domainA's DHCP server with domainB's DHCP server while still allowing clients from domainA and domainB to successfully
find domain controller of their own domain and being able to resolve hostnames from both domains?

When the devices on your network first request an IP address or reach the end of their leases (or you force them to check their lease is still valid) they will simply
broadcast a request for a DHCP server, and will accept an offer from the first DHCP server
to reply.
Multiple DHCP servers PT 1: Spanning multiple subnets.
If you have several VLANs or physical network segments that are separated into different subnets, and you want to provide a DHCP service to devices in all those subnets then there are two ways of doing this.
If the router / layer 3 switch separating them can act as a BOOTP/DHCP relay agent, then you can continue to keep all your DHCP server(s) in one or two central parts of your network and configure your DHCP server(s) to support multiple ranges of addresses.
In order to support this, your router or layer 3 switch must support the BOOTP relay agent specification covered in section
4 of RFC 1542.
If your router does not support RFC 1542 BOOTP relay agents, or if some of your network segments are geographically dispersed over slow links, then you will need to place one or more DHCP server in each subnet. This ‘local’ DHCP server will only serve its own
local segment’s requirements, and there is no interaction between it and other DHCP servers. If this is what you want then you can simply configure each DHCP server as a standalone server, with the details of the address pool for its own subnet, and not worry
about any other DHCP servers on other parts of the network. This is the most basic example of having more than one DHCP server on the same network.
http://www.arabitpro.com

DHCP Server configuration

Dear team,
Here is my DHCP configuration in Juniper route, but now i need to configure DHCP in windows 2008 r2 Server, kindly guide me witch is best way to go head.

Kumar
You no need to configure anything for clients when they are in same vlan or subnet of the DHCP Server. All you need to do for the other vlan clients that can be done by configuring ip helper in defualt gateway..consider
this as example..
DHCP Server 192.168.10.1 (vlan 10) ---------------------------- clients get ip because they are also vlan 10 192.168.10.5,,,,192.168.10.10 etc
other vlans, ex (vlan 20) your client ipconfig will be 192.168.20.1/24
default gateway will be 192.168.20.254 this will be in a switch Go to that interface in switch configure this ip helper address 192.168.10.1
it should work if my understanding is correct..
Thanks

SF/SG 300 DHCP server

Hi,
is it possible for SF/SG300 switches to be used as DHCP server for non-management VLAN-s.
The switch has VLAN1 as management VLAN - has IP address assigned.
The switch has additional VLAN - VLAN200 and I'd like SG300 to act as DHCP server for clients on this VLAN.
Is this possible at all?

Hi Jernej, the switch must operate in layer 3 mode. You can enable dhcp server per vlan.
To qualify to make a DHCP pool for a layer 3 vlan, none of the vlan interface can have an IP address issued via DHCP, so you vlan 1 and 200 must have a static ip address assigned. The vlan 1 does not require dhcp server configured for vlan 200 to have one.
Here is a sample configuration
config t
vlan database
vlan 200
exit
interface vlan 1
ip address 192.168.100.137 255.255.255.0
no ip address dhcp
exit
interface vlan 200
ip address 192.168.99.1 255.255.255.0
exit
ip dhcp server
ip dhcp pool network test
address low 192.168.99.1 high 192.168.99.254 255.255.255.0
default-router 192.168.99.1
dns-server 8.8.8.8
-Tom
Please mark answered for helpful posts

RV320 DHCP server

Serial Number:
Firmware Version:
v1.1.1.06 (2013-12-06, 11:02:37)
PID VID:
RV320 V01
Dear sir,
I got a issues, I have configure 2 VLAN on RV-320, VLAN 1 i have disable the DHCP, VLAN 25 i have configure DHCP Server enabled, but it seem DHCP bind on VLAN 25 is not working, then i try to config the static IP on device testing the VLAN is working, successful separate broadcast domain. and i can pint the VLAN 25 IP address, on DHCP i have re-enable VLAN 1 DHCP Server, it also working, successful assign the ip address to dynamic host.
any advise on my issues?
Thanks,

echolai@califor,
i had vlan disabled and vlan untagged for my RV320 in the lab, which would not hand out ip address for a different vlan. At this point at your earliest convenience open a support case so an engineer can look at the configuration in your router. If you like i can take a look at your config. Just send config to PM.

DHCP server and ip helper-address issue

Question,
By accident I had configured an IP HELPER-ADDRESS on a VLAN interface pointing to a DHCP server with an IP addrees in the same VLAN ( ip subnet ).
Some users had complaints and there were BAD ADDRESS entries in our DHCP server registered.
Can anyone explain to me why this is an issue please ?
My guess is that the the DHCP server receives the DHCPREQUEST from the client via the braodcast request and via the unicast request from the ip helper-address configuration. But does this really interfere with the DHCPACK and DHCPOFFER packets afterwards ?

Alex,
I've not been able to capture the network packets but I can understand if the server would send DHCPNACK requests ( wxhich would be a normal process ).
I just don't understand why so many users suddenly have issues and my DHCP scope is filling up with BAD ADDRESSES.
My assumption is that the client receives 2 valid DHCP responses ( one form the actual DHCP server and another one from the router, acting as DHCP relay agent ) and acknowledges them, but the DHCP process is somewhere corrupted ( either on the DHCP server or the DHCP client ).
I want a technical explanation for this issue :-)

Problems trying to migrating ports to a new Vlan using an externar DHCP server

Hello, here is the thing. I have the following configuration in my Core Switch:
interface Vlan1
ip address 10.24.74.1 255.255.254.0 secondary
ip address 192.0.2.54 255.255.255.0
ip helper-address 10.24.86.22
no ip redirects
As you see, we are using an external DHCP server for the Vlan1 and it is working:
Internet 192.0.2.98 0 3c97.0e23.3d8d ARPA Vlan1
Internet 192.0.2.194 0 e89a.8f77.36a0 ARPA Vlan1
Internet 192.0.2.195 0 e89a.8f77.01ab ARPA Vlan1
Internet 192.0.2.198 2 001c.25de.acaa ARPA Vlan1
Internet 192.0.2.199 0 d8eb.97a6.30a4 ARPA Vlan1
Internet 192.0.2.196 0 f0de.f1f1.1e06 ARPA Vlan1
Internet 192.0.2.203 0 e89a.8f77.016f ARPA Vlan1
Internet 192.0.2.207 4 d0c7.89d6.3ba3 ARPA Vlan1
Internet 192.0.2.211 0 4437.e636.7ef7 ARPA Vlan1
But, when a try to migrate this port to a new Vlan (Vlan50), I got the following issue:
001290: Jul 23 08:27:44.705 GMT: DHCPD: DHCPREQUEST received from client 013c.970e.233d.8d.
001291: Jul 23 08:27:44.705 GMT: DHCPD: client has moved to a new subnet.
001292: Jul 23 08:27:44.705 GMT: DHCPD: Sending DHCPNAK to client 013c.970e.233d.8d.
001293: Jul 23 08:27:44.705 GMT: DHCPD: broadcasting BOOTREPLY to client 3c97.0e23.3d8d.
001294: Jul 23 08:27:44.725 GMT: dhcp_snooping_get_ingress_port: Interface src_index 0xF
001295: Jul 23 08:27:44.725 GMT: DHCPD: DHCPDISCOVER received from client 013c.970e.233d.8d on interface Vlan50.
001296: Jul 23 08:27:44.725 GMT: DHCPD: there is no address pool for 10.24.76.1.
001297: Jul 23 08:27:44.725 GMT: DHCPD: setting giaddr to 10.24.76.1.
001298: Jul 23 08:27:44.725 GMT: DHCPD: BOOTREQUEST from 013c.970e.233d.8d forwarded to 10.24.86.21.
Any suggestions,
Thank you in advance,

Just to help someone who has the same issue.
I found this on the web site:
When the server receives a DHCPREQUEST from a client in the RENEWING (or REBINDING) state, it normally grants the renewal only if the client has an unexpired lease with this server. Otherwise the server ignores the request; the server to which the client is bound should answer the client. (The only exception is normally that if a server is sure the IP address the client is asking for is inappropriate for the client, the server will send a DHCPNAK, which forces the client back to the INIT state.)
Thank you anyway

Cisco 1702i WAP: how to get an interface in a non-native bridge group/ VLAN to be recognized by the internal DHCP server

Does anyone know how the internal DHCP server in these access points connects to virtual interfaces and bridges in the unit?
Is there some sort of default connection that connects the DHCP server to the native bridge group or VLAN?
In a test case, with an SSID in the native VLAN and bridge group, the 1702i serves an IP address to a wireless client no problem. But with a second SSID in a non native VLAN and bridge group, no IP gets served. My only guess is that since the bvi1 defaults to the native bridge group and VLAN, sub-interfaces also in this group are assumed to be in the same subnet as bvi1, or in this case:
interface bvi1
ip address 192.168.1.205 255.255.255.0
no ip route-cache
exit
It would be the ..1. subnet.
Since the dhcp pool is set as:
ip dhcp pool GeneralWiFi
network 192.168.1.0 255.255.255.0
lease 1
default-router 192.168.1.1
dns-server 8.8.8.8
exit
There may be an assumption that anything bvi1 can talk to is in the ..1. subnet, so the above pool gets activated on a request coming through bvi1.
Is the DHCP server just hanging out waiting for a request from an "area" that is assumed to be on the same subnet as the given pool?
Do I need to somehow show the device what subnet the 2nd SSID/ subinterfaces are in so the internal DHCP server can decide it needs to go to work, or is there some sort of bridging between the DHCP server and the interfaces that needs to be done? I am trying to use the same DHCP pool for the second subnet at this point, since I assume I will need another router to service an additional subnet and DHCP pool.

Keep in mind that DHCP is a broadcast packet to start. So the AP can only listen in the subnet that it has an IP address for.
Now, for any other subnet you can use the AP for DHCP but you have to have an IP helper address on your L3 pointing back to the AP.
That being said, I wouldn't use the DHCP server on the AP as it is limited. You'd be better off using a Microsoft server or some other device that is designed for DHCP.
HTH,
Steve

New VLan can't talk to DHCP server

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