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proc_configuring-an-external-dhcp-server.adoc

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Configuring an External DHCP Server to Use with {ProductName}

To configure an external DHCP server running {EL} to use with {ProductName}, you must install the ISC DHCP Service and Berkeley Internet Name Domain (BIND) utilities packages. You must also share the DHCP configuration and lease files with {ProductName}. The example in this procedure uses the distributed Network File System (NFS) protocol to share the DHCP configuration and lease files.

Note
 If you use dnsmasq as an external DHCP server, enable the dhcp-no-override setting. This is required because {Project} creates configuration files on the TFTP server under the grub2/ subdirectory. If the dhcp-no-override setting is disabled, clients fetch the bootloader and its configuration from the root directory, which might cause an error.
Procedure

  1. On your {EL} host, install the ISC DHCP Service and Berkeley Internet Name Domain (BIND) utilities packages:

    # {client-package-install-el8} dhcp-server bind-utils

  2. Generate a security token:

    # dnssec-keygen -a HMAC-MD5 -b 512 -n HOST omapi_key

    As a result, a key pair that consists of two files is created in the current directory.

  3. Copy the secret hash from the key:

    # grep ^Key Komapi_key.+*.private | cut -d ' ' -f2

  4. Edit the dhcpd configuration file for all subnets and add the key. The following is an example:

    # cat /etc/dhcp/dhcpd.conf
default-lease-time 604800;
max-lease-time 2592000;
log-facility local7;

subnet 192.168.38.0 netmask 255.255.255.0 {
	range 192.168.38.10 192.168.38.100;
	option routers 192.168.38.1;
	option subnet-mask 255.255.255.0;
	option domain-search "virtual.lan";
	option domain-name "virtual.lan";
	option domain-name-servers 8.8.8.8;
}

omapi-port 7911;
key omapi_key {
	algorithm HMAC-MD5;
	secret "jNSE5YI3H1A8Oj/tkV4...A2ZOHb6zv315CkNAY7DMYYCj48Umw==";
};
omapi-key omapi_key;

    Note that the option routers value is the {Project} or {SmartProxy} IP address that you want to use with an external DHCP service.

  5. Delete the two key files from the directory that they were created in.

  6. On {ProjectServer}, define each subnet. Do not set DHCP {SmartProxy} for the defined Subnet yet.

    To prevent conflicts, set up the lease and reservation ranges separately. For example, if the lease range is 192.168.38.10 to 192.168.38.100, in the {ProjectWebUI} define the reservation range as 192.168.38.101 to 192.168.38.250.

  7. Configure the firewall for external access to the DHCP server:

    # firewall-cmd --add-service dhcp \
&& firewall-cmd --runtime-to-permanent

  8. On {ProjectServer}, determine the UID and GID of the foreman user:

    # id -u foreman
993
# id -g foreman
990

  9. On the DHCP server, create the foreman user and group with the same IDs as determined in a previous step:

    # groupadd -g 990 foreman
# useradd -u 993 -g 990 -s /sbin/nologin foreman

  10. To ensure that the configuration files are accessible, restore the read and execute flags:

    # chmod o+rx /etc/dhcp/
# chmod o+r /etc/dhcp/dhcpd.conf
# chattr +i /etc/dhcp/ /etc/dhcp/dhcpd.conf

  11. Enable and start the DHCP service:

    # systemctl enable --now dhcpd

  12. Export the DHCP configuration and lease files using NFS:

    # {client-package-install-el8} {nfs-server-package}
# systemctl enable --now nfs-server

  13. Create directories for the DHCP configuration and lease files that you want to export using NFS:

    # mkdir -p /exports/var/lib/dhcpd /exports/etc/dhcp

  14. To create mount points for the created directories, add the following line to the /etc/fstab file:

    /var/lib/dhcpd /exports/var/lib/dhcpd none bind,auto 0 0
/etc/dhcp /exports/etc/dhcp none bind,auto 0 0

  15. Mount the file systems in /etc/fstab:

    # mount -a

  16. Ensure the following lines are present in /etc/exports:

    /exports 192.168.38.1(rw,async,no_root_squash,fsid=0,no_subtree_check)

/exports/etc/dhcp 192.168.38.1(ro,async,no_root_squash,no_subtree_check,nohide)

/exports/var/lib/dhcpd 192.168.38.1(ro,async,no_root_squash,no_subtree_check,nohide)

    Note that the IP address that you enter is the {Project} or {SmartProxy} IP address that you want to use with an external DHCP service.

  17. Reload the NFS server:

    # exportfs -rva

  18. Configure the firewall for DHCP omapi port 7911:

    # firewall-cmd --add-port=7911/tcp
# firewall-cmd --runtime-to-permanent

  19. Optional: Configure the firewall for external access to NFS. Clients are configured using NFSv3.

    # firewall-cmd --zone public --add-service mountd \
&& firewall-cmd --zone public --add-service rpc-bind \
&& firewall-cmd --zone public --add-service nfs \
&& firewall-cmd --runtime-to-permanent