dhcpd.conf fails to push options to fixed-address clients

[Kenneth Porter]

On 2/19/2022 8:51 AM, Simon wrote:
> What is in the leases file for 10.96.0.250 ?
Nothing whatsoever.
>
> Without digging out the book to check, I’m guessing that the server is sending a BOOTP response rather than a DHCP response. You have BOOTP enabled, so if that device previously had a BOOTP lease, then it’s possible the server is using the and ignoring what the client is asking for. You may have to remove any exiting leases for that device/address.
>
> I alway deny BOOTP, it’s a long time since I came across a device needing it, and as BOOTP has no concept of lease length, all BOOTP leases are effectively infinite which means network churn can leave you with no free leases. If you do have a device that needs it, you can allow it on a per-device basis.

Sounds logical. I changed "allow bootp" to "deny bootp" and the tcpdump 
looks the same. Still nothing in the lease file. The TP-Link router 
continues to issue a request about every 30 seconds.

Example exchange:


[root at orifice dhcpd]# tcpdump -i enp0s9 -vv -s 500 udp port bootps or 
udp port bootpc
tcpdump: listening on enp0s9, link-type EN10MB (Ethernet), capture size 
500 bytes
22:49:14.171212 IP (tos 0x0, ttl 64, id 22967, offset 0, flags [DF], 
proto UDP (17), length 399)
     10.96.0.250.bootpc > orifice.lsi.lan.bootps: [udp sum ok] 
BOOTP/DHCP, Request from 60:32:b1:a6:be:ac (oui Unknown), length 371,
           Client-IP 10.96.0.250
           Client-Ethernet-Address 60:32:b1:a6:be:ac (oui Unknown)
           Vendor-rfc1048 Extensions
             Magic Cookie 0x63825363
             DHCP-Message Option 53, length 1: Request
             Client-ID Option 61, length 7: ether 60:32:b1:a6:be:ac
             MSZ Option 57, length 2: 1024
             Parameter-Request Option 55, length 10:
               Subnet-Mask, Default-Gateway, Domain-Name-Server, Hostname
               Domain-Name, BR, Static-Route, NTP
               Classless-Static-Route, Classless-Static-Route-Microsoft
             Vendor-Class Option 60, length 8: "MSFT 5.0"
             Hostname Option 12, length 10: "ArcherAX20"
22:49:14.171673 IP (tos 0x0, ttl 64, id 12659, offset 0, flags [DF], 
proto UDP (17), length 328)
     orifice.lsi.lan.bootps > 10.96.0.250.bootpc: [bad udp cksum 0x1783 
-> 0xa0ef!] BOOTP/DHCP, Reply, length 300, xid 0x23b1a93f, Fl
           Client-IP 10.96.0.250
           Your-IP 10.96.0.250
           Server-IP orifice.lsi.lan
           Client-Ethernet-Address 60:32:b1:a6:be:ac (oui Unknown)
           file "pxelinux.0"[|bootp]