Question about dhcp on WAN & LAN



  • I am using SG-2440 2.3.2-RELEASE-p1, WAN interface connected to ISP's cable modem, LAN interface to switch, OPTx not used.

    In my dhcpd log I have an error, which reads in part```
    Sending on BPF/igb1/00:08:a2:0a:b1:bb/192.168.1.0/24
    Oct 29 14:13:31 dhcpd Can't bind to dhcp address: Address already in use
    Oct 29 14:13:31 dhcpd Please make sure there is no other dhcp server
    Oct 29 14:13:31 dhcpd running and that there's no entry for dhcp or
    Oct 29 14:13:31 dhcpd bootp in /etc/inetd.conf.

    
    I believe I am only running 1 dhcp server, unless perhaps the ISP cable modem is running one.  I have no access to that device and it is on a different subnet (192.168.100.1) so I would think it makes no difference.  Or does it?
    
    I used 'setup wizard' to set up SG-2440, it defaulted to WAN DHCP and since ISP provides a dhcp address, I assumed this was correct option.  I am wondering if that is the wrong choice. 
    
    The LAN setup defaulted to static, 192.168.1.1/24 and so I accepted that even though some LAN clients use DHCP.  I note that igb1 in the error msg is the LAN interface. Have I set this up incorrectly?  Should dhcp be on LAN and not WAN, and WAN be set to 192.168.1.1/24?
    
    My dhcp clients all have no problem access internet and IP's are what I expect.  Even if I do have this set up wrong, it seems to work ok.
    
    The above error msg refers to /etc/inetd.conf.  I cannot find that file using Diagnostics-> CmdPrompt "ls /etc/*.conf".  Where is that file located?
    
    If my setup is not right, what should I do to get it correct?

  • Netgate Administrator

    The most likely cause for that error is that the DHCP service on LAN tried to start twice. The second instance cannot use the already in-use socket so fails.

    If the LAN clients are receiving an IP address correctly then it's probably not causing an issue, it's mostly cosmetic.
    Are you still seeing that error after a reboot?

    It looks as though you have configured it correctly for your network.

    Steve



  • @stephenw10:

    The most likely cause for that error is that the DHCP service on LAN tried to start twice. The second instance cannot use the already in-use socket so fails.

    If the LAN clients are receiving an IP address correctly then it's probably not causing an issue, it's mostly cosmetic.
    Are you still seeing that error after a reboot?

    Steve:  Thank you, that helps my brain.  I don't see that error after a reboot, and today, I don't see that error at all during dhcp renewal.


  • Netgate Administrator

    Sounds like it was something transient then and only cosmetic anyway. That's the desired behaviour if for some reason it tries to start twice on the same interface.

    Keep an eye on the logs but if you don't see it again then you're all good.

    Steve


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