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

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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




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

    Posted 30 days ago

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




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

    Posted 30 days ago

    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