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Can someone share with me how to set options on dhcp server? I need to setup Option 43 for Cisco AP to find WiFi Controller.
Wednesday, January 23 2019, 03:04 AM
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  • Accepted Answer

    Wednesday, January 23 2019, 08:54 AM - #Permalink
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    Hello Greg,
    When setting extra options in dnsmasq, I suggest doing it in a file /etc/dnsmasq.d/any_name_you_like. You can see the format of the options in /etc/dnsmasq.d/dhcp.conf. It looks like you want something like:
    dhcp-option=enpXXX,43,some_string
    Where enpXXX is your LAN interface. Repeat the line for multiple LAN interfaces.
    The problem is the "some_string".

    From this Cisco Doc, you may just want a comma separated, quoted IP address list. Try both quoted and unquoted.

    After making your change, restart dnsmasq with "service dnsmasq restart".
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  • Accepted Answer

    Thursday, January 24 2019, 03:31 AM - #Permalink
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    Nick, thanks for your assistance. This is what I have so far:
    /etc/dnsmasq.d/wifi-dhcp-option
    option vendor-class-identifier "Cisco AP c1815"
    dhcp-option=enp2s0f1,43,"192.168.101.210"

    I've restarted the dhcp service but the AP does not appear to grab the option. Can you confirm that I have typed the lines correctly?
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  • Accepted Answer

    Thursday, January 24 2019, 08:42 AM - #Permalink
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    I'm not sure what the "option" line is doing. Does the dhcp-option need one or two IP's? I've tried googling around and not go anywhere particularly useful. You can see the dhcp-option parameter in the dnsmasq man pages. I would probably ask the Cisco people directly what they require.

    From the man pages and your attempt, I'd try:
    dhcp-option=enp2s0f1,vendor:Cisco AP c181543,192.168.101.210"
    I can't work out if the vendor is required or not. If not specified, does it send option 43 to to every DHCP response?
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  • Accepted Answer

    Thursday, February 14 2019, 02:13 PM - #Permalink
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    Hi Gregory,
    I was wondering if you had made any progress on this? I'd trying to do almost exactly the same thing, and have come up with using


    dhcp-vendorclass=cisco,Cisco
    dhcp-option=cisco,43,f1:04:c0:a8:00:ca


    Using dhcpdump to sniff the DHCP requests and responses looks prommising:-
    ---------------------------------------------------------------------------

    TIME: 2019-02-14 13:59:56.160
    IP: 0.0.0.0 (60:73:5c:2f:40:af) > 255.255.255.255 (ff:ff:ff:ff:ff:ff)
    OP: 1 (BOOTPREQUEST)
    HTYPE: 1 (Ethernet)
    HLEN: 6
    HOPS: 0
    XID: 000018b3
    SECS: 0
    FLAGS: 7f80
    CIADDR: 0.0.0.0
    YIADDR: 0.0.0.0
    SIADDR: 0.0.0.0
    GIADDR: 0.0.0.0
    CHADDR: 60:73:5c:2f:40:af:00:00:00:00:00:00:00:00:00:00
    SNAME: .
    FNAME: .
    OPTION: 53 ( 1) DHCP message type 3 (DHCPREQUEST)
    OPTION: 57 ( 2) Maximum DHCP message size 1200
    OPTION: 61 ( 7) Client-identifier 01:60:73:5c:2f:40:af
    OPTION: 54 ( 4) Server identifier 192.168.0.1
    OPTION: 50 ( 4) Request IP address 192.168.0.249
    OPTION: 12 ( 16) Host name AP6073.5c2f.40af
    OPTION: 55 ( 9) Parameter Request List 1 (Subnet mask)
    6 (DNS server)
    15 (Domainname)
    44 (NetBIOS name server)
    3 (Routers)
    7 (Log server)
    33 (Static route)
    150 (???)
    43 (Vendor specific info)

    OPTION: 60 ( 14) Vendor class identifier Cisco AP c1040
    ---------------------------------------------------------------------------

    TIME: 2019-02-14 13:59:56.160
    IP: 192.168.0.1 (0:25:b3:25:dc:42) > 255.255.255.255 (ff:ff:ff:ff:ff:ff)
    OP: 2 (BOOTPREPLY)
    HTYPE: 1 (Ethernet)
    HLEN: 6
    HOPS: 0
    XID: 000018b3
    SECS: 0
    FLAGS: 7f80
    CIADDR: 0.0.0.0
    YIADDR: 192.168.0.249
    SIADDR: 192.168.0.1
    GIADDR: 0.0.0.0
    CHADDR: 60:73:5c:2f:40:af:00:00:00:00:00:00:00:00:00:00
    SNAME: .
    FNAME: .
    OPTION: 53 ( 1) DHCP message type 5 (DHCPACK)
    OPTION: 54 ( 4) Server identifier 192.168.0.1
    OPTION: 51 ( 4) IP address leasetime 86400 (24h)
    OPTION: 58 ( 4) T1 43200 (12h)
    OPTION: 59 ( 4) T2 75600 (21h)
    OPTION: 15 ( 13) Domainname XXXXXXXXXXXXX
    OPTION: 43 ( 6) Vendor specific info f104c0a800ca ......
    OPTION: 6 ( 4) DNS server 192.168.0.1
    OPTION: 3 ( 4) Routers 192.168.0.1
    OPTION: 1 ( 4) Subnet mask 255.255.255.0
    ---------------------------------------------------------------------------


    The DHCP server seems to be passing the data I want it to, but the APs are still not finding the controller.
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  • Accepted Answer

    Friday, February 15 2019, 08:49 PM - #Permalink
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    Hi James, after trying many options, we connected to the physical AP via serial cable and manually pointed it to the Controller.
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