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  • 1.  CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Jan 19, 2024 10:27 AM

    Hi all

    We have a reproducable problem which affects all tested CX switches.

    In the past, with e.g. switches 2930f/m, a fast and effective way to test DHCP functionality was that we put one vlan to do IP DHCP client. If it gets an IP, DHCP works.

    With our CX switches, whenever I put the ip dhcp command on an interface vlan, it does not get an IP in the respective VLAN, even when DHCP is fully funcional on this vlan.

    I checked the captures and can see the DHCP discover, also the offer. But never the accept or further.

    As this is this widespread in our network (we have quite some CX switches), I ask myself if this is a bug or if we have something in the network (e.g. firewall or such) that prevents a successful DHCP negotiation. (I already checked some things, but narrowing it down is quite difficult, TBH)

    I also checked release notes and could not find anything about it.

    Does anyone experience the same or can give some insights?

    Tested on e.g. 6200F Switches with firmware 10.10.1080



  • 2.  RE: CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Jan 19, 2024 11:53 AM

    are you properly trunking the VLAN with the dhcp server running to the rest of your network? Trunking and access syntax is a bit different on those CX switches. Sometimes it's even as simple as a "no shut" on the vlan interface.

    test locally ... do you have a network port on the same switch, natively set to that VLAN, and and plug your client directly into that port?

    can you post your config?




  • 3.  RE: CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Jan 22, 2024 02:11 AM

    Hi

    The VLANs are trunked for sure and the DHCP is working fine. I even get an IP when connecting the client to the port with the access VLAN.

    The problem is at sites where I cannot get someone to test it for me or something alike. We did not have to get someone to test that with a client in the past with e.g. 2930f switches, that's why this function is so handy.

    ATM, I cannot post a config, I need to get clearance for that.

    Regards


    Original Message


  • 4.  RE: CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Jan 23, 2024 10:57 AM

    I thought you could only DHCP on the default VLan. This may have been changed through code versions. 


    Original Message


  • 5.  RE: CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Jan 23, 2024 11:18 AM

    Hi DubyaT

    Interesting thought, so I checked some manuals.

    This manual clearly says that you can to it on any interface vlan: https://www.arubanetworks.com/techdocs/AOS-CX/10.13/HTML/ip_services_8100-83xx-9300-10000/Content/Chp_DHCP/DHCP_cli_cmds/ip-dhc-10.htm
    But besides this one, I only found that it can be done on mgmt interface or it does not explicitly say you can do it on any interface vlan (it is always shown on VLAN 1).
    So, I checked the release notes and found nothing about this particular thing.

    I guess I'll open a TAC case.

    Regards


    Original Message


  • 6.  RE: CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Mar 31, 2026 05:40 AM

    Hi rkamer,

    Have you found a solution for this yet? I'm still experiencing the same issue across all CX models we have in production.

    For testing purposes, I occasionally enable DHCP on a specific VLAN to verify that all trunks are properly tagged.

    regards

    Nico

    -------------------------------------------

    Original Message


  • 7.  RE: CX switches do not get IPs with command ip dhcp on interface VLAN

    Posted Apr 01, 2026 06:56 AM

    If you upgrade to CX version 10.17, you can enable DHCP client on all VLANs:

    Feature overview

    ▪ Pre 10.17 releases supports only one VLAN interface enabled with DHCP client

    ▪ From 10.17 release, DHCPv4/v6 client can be active on multiple VLANs simultaneously

    ▪ DHCPv4/v6 client can be enabled on multiple VRFs simultaneously

    ▪ Preferred VLAN for DHCP attributes can be configured to have a predictable attribute selection

    ▪ Recommended limit is 32 active DHCP clients.

    ▪ For the lower -end platforms (4100i, 6000, 6100) recommended limit is 16 DHCP clients

    ▪ "ip dhcp option broadcast-flag" configuration must be enabled to successfully obtain DHCP IP across multiple VLANs when the default gateway is present.

    Check the attachment to this post for more details.



    ------------------------------
    Herman Robers
    ------------------------
    If you have urgent issues, always contact your HPE Aruba Networking partner, distributor, or Aruba TAC Support. Check https://www.arubanetworks.com/support-services/contact-support/ for how to contact HPE Aruba Networking TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or HPE Aruba Networking.

    In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
    ------------------------------

    Original Message


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