AP 1852 won't obtain requested IP Address

[mojobo]

After booting a AP1852 the dhcp process is running fine, the offered ip address is requested from the AP and the DHCP Server sends a Acknowledgement - which is received by the AP. The AP is not obtaining the IP Address but initiates a new DHCP Init. So the AP can not join an Controller.

There are two controllers.

One is DHCP Server for his joined APs- it sends a NAK to the affected AP and this is o.k..

The second is not configured as a DHCP Server. It forwards DHCP conversation in the network - a windows server is the responding DHCP Server.

Please see the following Log:

Is someone able to help?

[*08/06/2020 01:45:51.3406] ADDRCONF(NETDEV_UP): wired0: link is not ready

[*08/06/2020 01:45:51.6405] ADDRCONF(NETDEV_CHANGE): wired0: link becomes ready

[*08/06/2020 01:45:51.6505] wired0: 1000 Mbps Full Duplex

[*08/06/2020 01:45:51.6505]

[*08/06/2020 01:45:55.4493] Waiting for uplink IPv4 configuration

[*08/06/2020 01:45:56.6689] chatter: DHCP-EVT: Sending DHCP discover packet length 346 bytes

[*08/06/2020 01:45:56.6689] chatter: DHCP-PAK: Sent DHCP_DISCOVER pak:

[*08/06/2020 01:45:56.6689] chatter: sent pkt source: 0.0.0.0, destination: 255.255.255.255

[*08/06/2020 01:45:56.6689] chatter: UDP sport: 68, dport: 67, length: 312

[*08/06/2020 01:45:56.6689] chatter: DHCP op: 1, htype: 1, hlen: 6, hops: 0

[*08/06/2020 01:45:56.6689] chatter: xid: c0cbc614, secs: 0, flags: 128

[*08/06/2020 01:45:56.6689] chatter: client: 0.0.0.0, your: 0.0.0.0

[*08/06/2020 01:45:56.6689] chatter: srvr: 0.0.0.0, gw: 0.0.0.0

[*08/06/2020 01:45:56.7889] chatter: DHCP-EVT: Received DHCP msg type: 2 from server: 10.17.48.203

[*08/06/2020 01:45:56.7889] chatter: DHCP-EVT: DHCP client machine state: init

[*08/06/2020 01:45:56.7889] chatter: DHCP-PAK: Received DHCP_OFFER pak:

[*08/06/2020 01:45:56.7889] chatter: rcvd pkt source: 10.17.48.203, destination: 255.255.255.255

[*08/06/2020 01:45:56.7889] chatter: UDP sport: 67, dport: 68, length: 321

[*08/06/2020 01:45:56.7889] chatter: DHCP op: 2, htype: 1, hlen: 6, hops: 0

[*08/06/2020 01:45:56.7889] chatter: DHCP server identifier: 10.17.48.203

[*08/06/2020 01:45:56.7889] chatter: xid: c0cbc614, secs: 0, flags: 128

[*08/06/2020 01:45:56.7889] chatter: client: 0.0.0.0, your: 192.168.100.215

[*08/06/2020 01:45:56.7889] chatter: srvr: 10.17.48.203, gw: 192.168.100.254

[*08/06/2020 01:45:56.7889] chatter: DHCP-PAK: Sent DHCP_REQUEST pak:

[*08/06/2020 01:45:56.7889] chatter: sent pkt source: 0.0.0.0, destination: 255.255.255.255

[*08/06/2020 01:45:56.7889] chatter: UDP sport: 68, dport: 67, length: 318

[*08/06/2020 01:45:56.7889] chatter: DHCP server identifier: 10.17.48.203

[*08/06/2020 01:45:56.7889] chatter: Request DHCP IP: 192.168.100.215

[*08/06/2020 01:45:56.7889] chatter: DHCP-EVT: Sending DHCP request packet length 352 bytes

[*08/06/2020 01:45:56.8189] chatter: DHCP-EVT: Received DHCP msg type: 6 from server: 192.168.100.50

[*08/06/2020 01:45:56.8189] chatter: DHCP-EVT: DHCP client machine state: requesting

[*08/06/2020 01:45:56.8588] chatter: DHCP-EVT: Received DHCP msg type: 5 from server: 10.17.48.203

[*08/06/2020 01:45:56.8588] chatter: DHCP-EVT: DHCP client machine state: init

[*08/06/2020 01:46:00.4577] Waiting for uplink IPv4 configuration

[*08/06/2020 01:46:05.4562] Waiting for uplink IPv4 configuration

[Leo Laohoo]

Factory-reset the AP using the command "capwap ap erase all".

Is the IP helper address pointing to the physical DHCP server or is it pointing to a "virtual" IP address?

[mojobo]

Leo, Thank you for answering. I made the factory reset but this did not help.

I think in this situation an IP Helper is not necessary. The AP behaves like a normal Client.

[Rich R · Accepted solution]

[*08/06/2020 01:45:56.8189] chatter: DHCP-EVT: Received DHCP msg type: 6 from server: 192.168.100.50
type 6 = DHCPRELEASE - that's weird but doesn't seem to be the problem

[*08/06/2020 01:45:56.8588] chatter: DHCP-EVT: Received DHCP msg type: 5 from server: 10.17.48.203
type 5 = DHCPNAK - the server is NAKing the IP it offered!  Maybe the release message from the other server is causing that.  The AP is behaving correctly in this case.  Because it received NAK from the server it starts DORA again.

Would need to see a full packet capture of these packets and detailed logs from both servers to understand why this is happening but having two opposing servers on the same subnet clearly is not a good idea!

[mojobo]

Thank you for answering. Your hint regarding the two dhcp servers in one network made the success.

I eliminated the second DHCP server - and the AP accepted the IP Address and joined the controller.