DHCP option 82 is required for dhcp?

[eigrpy]

Hi, DHCP option 82 is an option. We did not configure it on WLC and it seems working well. but recently we found some clients cannot get ip address. After debug ip dhcp on switch dhcp, it was found that dhcp option 82 is not present. So I want to know if the option 82 is required for the client to get ip address? or in what situation we need to configure dhcp option 82? Thank you

[balaji.bandi]

check this explanation :

https://mrncciew.com/2013/05/18/understanding-dhcp-option-82/

https://www.cisco.com/c/en/us/td/docs/wireless/controller/7-4/configuration/guides/consolidated/b_cg74_CONSOLIDATED/b_cg74_CONSOLIDATED_chapter_010110010.html

[eigrpy]

Client cannot get ip. Can we say adding option82 can resolve the issue? 

[balaji.bandi]

at this stage, we are not sure how your environment configured, but configuring Option 82 not going to harm ( but as i mentioned this may or may not a fix issue).

if still not working we need to se how your helper-address configured to get IP address from WLC? enable-debug to see what is wrong and post completely debug here for us to understand correctly.

[MHM Cisco World]

https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/113302-dhcp-option82-00.html

according to client op 82 we can give each group of client a specific range from subnet

[eigrpy]

The below is only debug ip dhcp info I have now. Please let me know what other debug is needed

*Mar 19 22:47:23.288: Option 82 not present
*Mar 19 22:47:23.288: DHCPD: Reload workspace interface Vlan40 tableid 0.
*Mar 19 22:47:23.288: DHCPD: tableid for 10.1.218.1 on Vlan40 is 0
*Mar 19 22:47:23.288: DHCPD: client's VPN is .
*Mar 19 22:47:23.288: DHCPD: No option 125
*Mar 19 22:47:23.288: DHCPD: DHCPREQUEST received from client 0140.665c.7116.9e.
*Mar 19 22:47:23.288: DHCPD: DHCPREQUEST received on interface Vlan40.
*Mar 19 22:47:23.288: DHCPD: FSM state change INVALID
*Mar 19 22:47:23.288: DHCPD: Workspace state changed from INIT to INVALID
*Mar 19 22:47:23.288: DHCPD: Client either rebooted or rebinding we are seeing the client for first time
*Mar 19 22:47:23.288: DHCPD: excluded address: 10.1.218.126
*Mar 19 22:47:23.288: DHCPD: Finding a relay for client 0140.665c.7116.9e on interface Vlan40.
*Mar 19 22:47:23.288: DHCPD : Locating relay for Subnet 10.1.218.1
*Mar 19 22:47:23.289: DHCPD: Looking up binding using address 10.1.218.1
*Mar 19 22:47:23.289: DHCPD: setting giaddr to 10.1.218.1.
*Mar 19 22:47:23.289: DHCPD: BOOTREQUEST from 0140.665c.7116.9e forwarded to 10.1.218.6.
*Mar 19 22:47:23.289: DHCPD: BOOTREQUEST from 0140.665c.7116.9e forwarded to 10.1.218.5.
*Mar 19 22:47:23.290: Option 82 not present
*Mar 19 22:47:23.290: DHCPD: Reload workspace interface Vlan40 tableid 0.
*Mar 19 22:47:23.290: DHCPD: tableid for 10.1.218.1 on Vlan40 is 0
*Mar 19 22:47:23.290: DHCPD: client's VPN is .
*Mar 19 22:47:23.291: DHCPD: No option 125
*Mar 19 22:47:23.291: DHCPD: forwarding BOOTREPLY to client 408d.6671.169e.
*Mar 19 22:47:23.291: DHCPD: Forwarding reply on numbered intf
*Mar 19 22:47:23.291: DHCPD: Option 125 not present in the msg.
*Mar 19 22:47:23.291: DHCPD: Clearing unwanted ARP entries for multiple helpers
*Mar 19 22:47:23.291: DHCPD: src nbma addr as zero
*Mar 19 22:47:23.291: DHCPD: ARP entry exists (10.1.218.126, 408d.6611.169e).
*Mar 19 22:47:23.291: DHCPD: egress Interfce Vlan40

[MHM Cisco World]

Cisco Bug: CSCvo65701 - WLC randomly updating ARP entry with incorrect type