Device receives another IP - wlc9800

[lizochkanovichenko]

Hello!

I have noticed that some devices have been assigned a different IP address than their network. Corporate PCs recieve IP-address from network 10.148.x.x but PCs recieve IP-address from another network - 192.168.x.x. 

For example,

For this WLAN the dhcp Required is disable. 

Could there be a problem with this? But then why do other devices get the correct IP?
I also deleted such clients from the controller, they reconnected and received the correct IP address.

Thanks in advance! 

Have a nice day! 

[marce1000]

     >...but PCs receive IP-address from another network - 192.168.x.x. 
   - 192.168.x.x is a link local address , that only means that no address could be obtained from a DHCP server

   + Start with an overall checkup of the wlc9800 configuration with the CLI command show tech wireless
      and feed the output from that into Wireless Config Analyzer
      Do not use a simple show tech as input for this procedure.

  + For best DHCP setups look at : https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/technical-reference/c9800-best-practices.html#DHCPbridgingandDHCPrelay

  + Look at client health using  : https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/217738-monitor-catalyst-9800-kpis-key-performa.html#anc5  when making changes (before or after)

 +   - Further engage in full client debugging according to https://logadvisor.cisco.com/logadvisor/wireless/9800/9800ClientConnectivity , these debugs can be analyzed with Wireless Debug Analyzer   (for those clients who can not obtain an IP address through DHCP)

  M.

[Rich R]

DHCP required forces a client to initiate a DHCP request after it joins the WiFi because any traffic sent from any other IP will be dropped.
DHCP not required means clients can use static IP if they want to, or some dumb clients will not renew DHCP on joining so may try to use the same IP they were using from a previous connection.  Basically the client can use any IP they want to even if it doesn't work. If you want clients to use DHCP then you should set DHCP required.

Make sure your software is up to date as per TAC recommended link below.

[lizochkanovichenko]

Hello everyone!

@Rich R @marce1000 

I added ip-helper address on SVI, eneble Relay Information Option and specified Source-Interface Vlan. Also I enable IPv4 DHCP Required but I didn't specified DHCP Server IP Address because we have two DHCP and I can't add both ip. 

I see then problem don't solve. What else do I need to do?

Thanks in advance! 

[marce1000]

       - Did you execute  the  checkup of the wlc9800 configuration with the CLI command show tech wireless
      feeding  the  the output from that into Wireless Config Analyzer
                        (Do not use a simple show tech as input for this procedure)

      - You will (also) need to fully debug a (problem)  client using instructions from https://logadvisor.cisco.com/logadvisor/wireless/9800/9800ClientConnectivity    
           you can have client debugs analyzed with Wireless Debug Analyzer

   M.

[MHM Cisco World]

can I see the config of ip helper 

MHM

[lizochkanovichenko]

Hello!

There:

interface VlanX
ip dhcp relay information trusted
ip dhcp relay source-interface VlanX
ip address 10.x.x.x x.x.x.x secondary
ip address 10.x.x.x x.x.x.x
ip helper-address 10.y.y.y
ip helper-address 10.y.y.y
end

[MHM Cisco World]

Vlan SVI mgmt use for WLC not for wifi client'

You need to add ip helper under vlan svi of wifi client 

MHM

[marce1000]

  - What you could do to test the DHCP server availability on the intended WLAN/VLAN is put a laptop in that same VLAN on the
     wired network and check if it can obtain an ip address through DHCP , 

 M.

[lizochkanovichenko]

Hello!

@marce1000 

Yes, PC obtain an ip address through DHCP in Wired. And also I have old WLC5508 in our network and there is no problem here. I notice problem in WLC 9800. 

[marce1000]

                   >.....Yes, PC obtain an ip address through DHCP in Wired

   - Strange then you must delve into deep client debugging according to +     https://logadvisor.cisco.com/logadvisor/wireless/9800/9800ClientConnectivity , these debugs can be analyzed with Wireless Debug Analyzer   (for those clients who can not obtain an IP address through DHCP)

  M.

[Rich R]

As @MHM Cisco World pointed out you should not have any helper or DHCP relay info on your WLC AP management interface!  That is done purely on your switch/router client interface (9500 in your case).

Run a radioactive trace when a client connects and run a packet capture on the 9500 client interface to confirm the DHCP requests are reaching the 9500.  Also packet capture on packets to and from DHCP server to make sure DHCP requests are being relayed and replies are being received.

[lizochkanovichenko]

@MHM Cisco World 

WLC connect to Cisco Catalyst 9500. C9500 have interface vlan for wifi client and have ip helper addrress. In WLC I created only mgmt vlan, another vlan I just announced. If I creat vlan for for wifi client what address should I enter?

Thanks. 

[MHM Cisco World]

then friend no need ip helper under mgmt vlan in WLC 
you need ip helper in C9500 VLAN SVI 
MHM

[lizochkanovichenko]

The ip helper adress is SVI for wifi client in C9500. There:

interface VlanX
ip address 10.x.x.x x.x.x.x
ip helper-address 10.y.y.y
ip helper-address 10.y.y.y
end