diff --git a/smoketest/scripts/cli/test_service_dhcp-server.py b/smoketest/scripts/cli/test_service_dhcp-server.py
index 093e43494..91ae901cd 100755
--- a/smoketest/scripts/cli/test_service_dhcp-server.py
+++ b/smoketest/scripts/cli/test_service_dhcp-server.py
@@ -1,489 +1,496 @@
 #!/usr/bin/env python3
 #
 # Copyright (C) 2020-2021 VyOS maintainers and contributors
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 or later as
 # published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import unittest
 
 from base_vyostest_shim import VyOSUnitTestSHIM
 
 from vyos.configsession import ConfigSessionError
 from vyos.utils.process import process_named_running
 from vyos.utils.file import read_file
 from vyos.template import address_from_cidr
 from vyos.template import inc_ip
 from vyos.template import dec_ip
 from vyos.template import netmask_from_cidr
 
 PROCESS_NAME = 'dhcpd'
 DHCPD_CONF = '/run/dhcp-server/dhcpd.conf'
 base_path = ['service', 'dhcp-server']
 subnet = '192.0.2.0/25'
 router = inc_ip(subnet, 1)
 dns_1 = inc_ip(subnet, 2)
 dns_2 = inc_ip(subnet, 3)
 domain_name = 'vyos.net'
 
 class TestServiceDHCPServer(VyOSUnitTestSHIM.TestCase):
     @classmethod
     def setUpClass(cls):
         super(TestServiceDHCPServer, cls).setUpClass()
 
         cidr_mask = subnet.split('/')[-1]
         cls.cli_set(cls, ['interfaces', 'dummy', 'dum8765', 'address', f'{router}/{cidr_mask}'])
 
     @classmethod
     def tearDownClass(cls):
         cls.cli_delete(cls, ['interfaces', 'dummy', 'dum8765'])
         super(TestServiceDHCPServer, cls).tearDownClass()
 
     def tearDown(self):
         self.cli_delete(base_path)
         self.cli_commit()
 
     def test_dhcp_single_pool_range(self):
         shared_net_name = 'SMOKE-1'
 
         range_0_start = inc_ip(subnet, 10)
         range_0_stop  = inc_ip(subnet, 20)
         range_1_start = inc_ip(subnet, 40)
         range_1_stop  = inc_ip(subnet, 50)
 
         self.cli_set(base_path + ['dynamic-dns-update'])
 
         pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
         # we use the first subnet IP address as default gateway
         self.cli_set(pool + ['default-router', router])
         self.cli_set(pool + ['name-server', dns_1])
         self.cli_set(pool + ['name-server', dns_2])
         self.cli_set(pool + ['domain-name', domain_name])
         self.cli_set(pool + ['ping-check'])
 
         # check validate() - No DHCP address range or active static-mapping set
         with self.assertRaises(ConfigSessionError):
             self.cli_commit()
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
         self.cli_set(pool + ['range', '1', 'start', range_1_start])
         self.cli_set(pool + ['range', '1', 'stop', range_1_stop])
 
         # commit changes
         self.cli_commit()
 
         config = read_file(DHCPD_CONF)
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
         self.assertIn(f'ddns-update-style interim;', config)
         self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
         self.assertIn(f'option domain-name-servers {dns_1}, {dns_2};', config)
         self.assertIn(f'option routers {router};', config)
         self.assertIn(f'option domain-name "{domain_name}";', config)
         self.assertIn(f'default-lease-time 86400;', config)
         self.assertIn(f'max-lease-time 86400;', config)
         self.assertIn(f'ping-check true;', config)
         self.assertIn(f'range {range_0_start} {range_0_stop};', config)
         self.assertIn(f'range {range_1_start} {range_1_stop};', config)
         self.assertIn(f'set shared-networkname = "{shared_net_name}";', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_single_pool_options(self):
         shared_net_name = 'SMOKE-0815'
 
         range_0_start       = inc_ip(subnet, 10)
         range_0_stop        = inc_ip(subnet, 20)
         smtp_server         = '1.2.3.4'
         time_server         = '4.3.2.1'
         tftp_server         = 'tftp.vyos.io'
         search_domains      = ['foo.vyos.net', 'bar.vyos.net']
         bootfile_name       = 'vyos'
         bootfile_server     = '192.0.2.1'
         wpad                = 'http://wpad.vyos.io/foo/bar'
         server_identifier   = bootfile_server
         ipv6_only_preferred = '300'
 
         pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
         # we use the first subnet IP address as default gateway
         self.cli_set(pool + ['default-router', router])
         self.cli_set(pool + ['name-server', dns_1])
         self.cli_set(pool + ['name-server', dns_2])
         self.cli_set(pool + ['domain-name', domain_name])
         self.cli_set(pool + ['ip-forwarding'])
         self.cli_set(pool + ['smtp-server', smtp_server])
         self.cli_set(pool + ['pop-server', smtp_server])
         self.cli_set(pool + ['time-server', time_server])
         self.cli_set(pool + ['tftp-server-name', tftp_server])
         for search in search_domains:
             self.cli_set(pool + ['domain-search', search])
         self.cli_set(pool + ['bootfile-name', bootfile_name])
         self.cli_set(pool + ['bootfile-server', bootfile_server])
         self.cli_set(pool + ['wpad-url', wpad])
         self.cli_set(pool + ['server-identifier', server_identifier])
 
         self.cli_set(pool + ['static-route', '10.0.0.0/24', 'next-hop', '192.0.2.1'])
         self.cli_set(pool + ['ipv6-only-preferred', ipv6_only_preferred])
 
         # check validate() - No DHCP address range or active static-mapping set
         with self.assertRaises(ConfigSessionError):
             self.cli_commit()
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
 
         # commit changes
         self.cli_commit()
 
         config = read_file(DHCPD_CONF)
 
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
         self.assertIn(f'ddns-update-style none;', config)
         self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
         self.assertIn(f'option domain-name-servers {dns_1}, {dns_2};', config)
         self.assertIn(f'option routers {router};', config)
         self.assertIn(f'option domain-name "{domain_name}";', config)
 
         search = '"' + ('", "').join(search_domains) + '"'
         self.assertIn(f'option domain-search {search};', config)
 
         self.assertIn(f'option ip-forwarding true;', config)
         self.assertIn(f'option smtp-server {smtp_server};', config)
         self.assertIn(f'option pop-server {smtp_server};', config)
         self.assertIn(f'option time-servers {time_server};', config)
         self.assertIn(f'option wpad-url "{wpad}";', config)
         self.assertIn(f'option dhcp-server-identifier {server_identifier};', config)
         self.assertIn(f'option tftp-server-name "{tftp_server}";', config)
         self.assertIn(f'option bootfile-name "{bootfile_name}";', config)
         self.assertIn(f'filename "{bootfile_name}";', config)
         self.assertIn(f'next-server {bootfile_server};', config)
         self.assertIn(f'default-lease-time 86400;', config)
         self.assertIn(f'max-lease-time 86400;', config)
         self.assertIn(f'range {range_0_start} {range_0_stop};', config)
         self.assertIn(f'set shared-networkname = "{shared_net_name}";', config)
         self.assertIn(f'option rfc8925-ipv6-only-preferred {ipv6_only_preferred};', config)
 
         # weird syntax for those static routes
         self.assertIn(f'option rfc3442-static-route 24,10,0,0,192,0,2,1, 0,192,0,2,1;', config)
         self.assertIn(f'option windows-static-route 24,10,0,0,192,0,2,1;', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_single_pool_static_mapping(self):
         shared_net_name = 'SMOKE-2'
         domain_name = 'private'
 
         pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
         # we use the first subnet IP address as default gateway
         self.cli_set(pool + ['default-router', router])
         self.cli_set(pool + ['name-server', dns_1])
         self.cli_set(pool + ['name-server', dns_2])
         self.cli_set(pool + ['domain-name', domain_name])
 
         # check validate() - No DHCP address range or active static-mapping set
         with self.assertRaises(ConfigSessionError):
             self.cli_commit()
 
         client_base = 10
         for client in ['client1', 'client2', 'client3']:
             mac = '00:50:00:00:00:{}'.format(client_base)
             self.cli_set(pool + ['static-mapping', client, 'mac-address', mac])
             self.cli_set(pool + ['static-mapping', client, 'ip-address', inc_ip(subnet, client_base)])
             client_base += 1
 
+        # cannot have mappings with duplicate IP addresses
+        with self.assertRaises(ConfigSessionError):
+            self.cli_set(pool + ['static-mapping', 'dupe1', 'mac', '00:50:00:00:00:01'])
+            self.cli_set(pool + ['static-mapping', 'dupe1', 'ip-address', inc_ip(subnet, 10)])
+            self.cli_commit()
+        self.cli_delete(pool + ['static-mapping', 'dupe1'])
+
         # commit changes
         self.cli_commit()
 
         config = read_file(DHCPD_CONF)
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
         self.assertIn(f'ddns-update-style none;', config)
         self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
         self.assertIn(f'option domain-name-servers {dns_1}, {dns_2};', config)
         self.assertIn(f'option routers {router};', config)
         self.assertIn(f'option domain-name "{domain_name}";', config)
         self.assertIn(f'default-lease-time 86400;', config)
         self.assertIn(f'max-lease-time 86400;', config)
 
         client_base = 10
         for client in ['client1', 'client2', 'client3']:
             mac = '00:50:00:00:00:{}'.format(client_base)
             ip = inc_ip(subnet, client_base)
             self.assertIn(f'host {shared_net_name}_{client}' + ' {', config)
             self.assertIn(f'fixed-address {ip};', config)
             self.assertIn(f'hardware ethernet {mac};', config)
             client_base += 1
 
         self.assertIn(f'set shared-networkname = "{shared_net_name}";', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_multiple_pools(self):
         lease_time = '14400'
 
         for network in ['0', '1', '2', '3']:
             shared_net_name = f'VyOS-SMOKETEST-{network}'
             subnet = f'192.0.{network}.0/24'
             router = inc_ip(subnet, 1)
             dns_1 = inc_ip(subnet, 2)
 
             range_0_start = inc_ip(subnet, 10)
             range_0_stop  = inc_ip(subnet, 20)
             range_1_start = inc_ip(subnet, 30)
             range_1_stop  = inc_ip(subnet, 40)
 
             pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
             # we use the first subnet IP address as default gateway
             self.cli_set(pool + ['default-router', router])
             self.cli_set(pool + ['name-server', dns_1])
             self.cli_set(pool + ['domain-name', domain_name])
             self.cli_set(pool + ['lease', lease_time])
 
             self.cli_set(pool + ['range', '0', 'start', range_0_start])
             self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
             self.cli_set(pool + ['range', '1', 'start', range_1_start])
             self.cli_set(pool + ['range', '1', 'stop', range_1_stop])
 
             client_base = 60
             for client in ['client1', 'client2', 'client3', 'client4']:
                 mac = '02:50:00:00:00:{}'.format(client_base)
                 self.cli_set(pool + ['static-mapping', client, 'mac-address', mac])
                 self.cli_set(pool + ['static-mapping', client, 'ip-address', inc_ip(subnet, client_base)])
                 client_base += 1
 
         # commit changes
         self.cli_commit()
 
         config = read_file(DHCPD_CONF)
         for network in ['0', '1', '2', '3']:
             shared_net_name = f'VyOS-SMOKETEST-{network}'
             subnet = f'192.0.{network}.0/24'
             router = inc_ip(subnet, 1)
             dns_1 = inc_ip(subnet, 2)
 
             range_0_start = inc_ip(subnet, 10)
             range_0_stop  = inc_ip(subnet, 20)
             range_1_start = inc_ip(subnet, 30)
             range_1_stop  = inc_ip(subnet, 40)
 
             network = address_from_cidr(subnet)
             netmask = netmask_from_cidr(subnet)
 
             self.assertIn(f'ddns-update-style none;', config)
             self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
             self.assertIn(f'option domain-name-servers {dns_1};', config)
             self.assertIn(f'option routers {router};', config)
             self.assertIn(f'option domain-name "{domain_name}";', config)
             self.assertIn(f'default-lease-time {lease_time};', config)
             self.assertIn(f'max-lease-time {lease_time};', config)
             self.assertIn(f'range {range_0_start} {range_0_stop};', config)
             self.assertIn(f'range {range_1_start} {range_1_stop};', config)
             self.assertIn(f'set shared-networkname = "{shared_net_name}";', config)
 
             client_base = 60
             for client in ['client1', 'client2', 'client3', 'client4']:
                 mac = '02:50:00:00:00:{}'.format(client_base)
                 ip = inc_ip(subnet, client_base)
                 self.assertIn(f'host {shared_net_name}_{client}' + ' {', config)
                 self.assertIn(f'fixed-address {ip};', config)
                 self.assertIn(f'hardware ethernet {mac};', config)
                 client_base += 1
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_exclude_not_in_range(self):
         # T3180: verify else path when slicing DHCP ranges and exclude address
         # is not part of the DHCP range
         range_0_start = inc_ip(subnet, 10)
         range_0_stop  = inc_ip(subnet, 20)
 
         pool = base_path + ['shared-network-name', 'EXCLUDE-TEST', 'subnet', subnet]
         self.cli_set(pool + ['default-router', router])
         self.cli_set(pool + ['exclude', router])
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
 
         # commit changes
         self.cli_commit()
 
         # VErify
         config = read_file(DHCPD_CONF)
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
 
         self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
         self.assertIn(f'option routers {router};', config)
         self.assertIn(f'range {range_0_start} {range_0_stop};', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_exclude_in_range(self):
         # T3180: verify else path when slicing DHCP ranges and exclude address
         # is not part of the DHCP range
         range_0_start = inc_ip(subnet, 10)
         range_0_stop  = inc_ip(subnet, 100)
 
         # the DHCP exclude addresse is blanked out of the range which is done
         # by slicing one range into two ranges
         exclude_addr  = inc_ip(range_0_start, 20)
         range_0_stop_excl = dec_ip(exclude_addr, 1)
         range_0_start_excl = inc_ip(exclude_addr, 1)
 
         pool = base_path + ['shared-network-name', 'EXCLUDE-TEST-2', 'subnet', subnet]
         self.cli_set(pool + ['default-router', router])
         self.cli_set(pool + ['exclude', exclude_addr])
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
 
         # commit changes
         self.cli_commit()
 
         # Verify
         config = read_file(DHCPD_CONF)
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
 
         self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
         self.assertIn(f'option routers {router};', config)
         self.assertIn(f'range {range_0_start} {range_0_stop_excl};', config)
         self.assertIn(f'range {range_0_start_excl} {range_0_stop};', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_relay_server(self):
         # Listen on specific address and return DHCP leases from a non
         # directly connected pool
         self.cli_set(base_path + ['listen-address', router])
 
         relay_subnet = '10.0.0.0/16'
         relay_router = inc_ip(relay_subnet, 1)
 
         range_0_start = '10.0.1.0'
         range_0_stop  = '10.0.250.255'
 
         pool = base_path + ['shared-network-name', 'RELAY', 'subnet', relay_subnet]
         self.cli_set(pool + ['default-router', relay_router])
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
 
         # commit changes
         self.cli_commit()
 
         config = read_file(DHCPD_CONF)
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
         # Check the relay network
         self.assertIn(f'subnet {network} netmask {netmask}' + r' { }', config)
 
         relay_network = address_from_cidr(relay_subnet)
         relay_netmask = netmask_from_cidr(relay_subnet)
         self.assertIn(f'subnet {relay_network} netmask {relay_netmask}' + r' {', config)
         self.assertIn(f'option routers {relay_router};', config)
         self.assertIn(f'range {range_0_start} {range_0_stop};', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_invalid_raw_options(self):
         shared_net_name = 'SMOKE-5'
 
         range_0_start = inc_ip(subnet, 10)
         range_0_stop  = inc_ip(subnet, 20)
 
         pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
         # we use the first subnet IP address as default gateway
         self.cli_set(pool + ['default-router', router])
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
 
         self.cli_set(base_path + ['global-parameters', 'this-is-crap'])
         # check generate() - dhcpd should not acceot this garbage config
         with self.assertRaises(ConfigSessionError):
             self.cli_commit()
         self.cli_delete(base_path + ['global-parameters'])
 
         # commit changes
         self.cli_commit()
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
     def test_dhcp_failover(self):
         shared_net_name = 'FAILOVER'
         failover_name = 'VyOS-Failover'
 
         range_0_start = inc_ip(subnet, 10)
         range_0_stop  = inc_ip(subnet, 20)
 
         pool = base_path + ['shared-network-name', shared_net_name, 'subnet', subnet]
         # we use the first subnet IP address as default gateway
         self.cli_set(pool + ['default-router', router])
 
         # check validate() - No DHCP address range or active static-mapping set
         with self.assertRaises(ConfigSessionError):
             self.cli_commit()
         self.cli_set(pool + ['range', '0', 'start', range_0_start])
         self.cli_set(pool + ['range', '0', 'stop', range_0_stop])
 
         # failover
         failover_local = router
         failover_remote = inc_ip(router, 1)
 
         self.cli_set(base_path + ['failover', 'source-address', failover_local])
         self.cli_set(base_path + ['failover', 'name', failover_name])
         self.cli_set(base_path + ['failover', 'remote', failover_remote])
         self.cli_set(base_path + ['failover', 'status', 'primary'])
 
         # check validate() - failover needs to be enabled for at least one subnet
         with self.assertRaises(ConfigSessionError):
             self.cli_commit()
         self.cli_set(pool + ['enable-failover'])
 
         # commit changes
         self.cli_commit()
 
         config = read_file(DHCPD_CONF)
 
         self.assertIn(f'failover peer "{failover_name}"' + r' {', config)
         self.assertIn(f'primary;', config)
         self.assertIn(f'mclt 1800;', config)
         self.assertIn(f'mclt 1800;', config)
         self.assertIn(f'split 128;', config)
         self.assertIn(f'port 647;', config)
         self.assertIn(f'peer port 647;', config)
         self.assertIn(f'max-response-delay 30;', config)
         self.assertIn(f'max-unacked-updates 10;', config)
         self.assertIn(f'load balance max seconds 3;', config)
         self.assertIn(f'address {failover_local};', config)
         self.assertIn(f'peer address {failover_remote};', config)
 
         network = address_from_cidr(subnet)
         netmask = netmask_from_cidr(subnet)
         self.assertIn(f'ddns-update-style none;', config)
         self.assertIn(f'subnet {network} netmask {netmask}' + r' {', config)
         self.assertIn(f'option routers {router};', config)
         self.assertIn(f'range {range_0_start} {range_0_stop};', config)
         self.assertIn(f'set shared-networkname = "{shared_net_name}";', config)
         self.assertIn(f'failover peer "{failover_name}";', config)
         self.assertIn(f'deny dynamic bootp clients;', config)
 
         # Check for running process
         self.assertTrue(process_named_running(PROCESS_NAME))
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)
diff --git a/src/conf_mode/service_dhcp-server.py b/src/conf_mode/service_dhcp-server.py
index ac7d95632..8d849b1e6 100755
--- a/src/conf_mode/service_dhcp-server.py
+++ b/src/conf_mode/service_dhcp-server.py
@@ -1,328 +1,334 @@
 #!/usr/bin/env python3
 #
 # Copyright (C) 2018-2023 VyOS maintainers and contributors
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 or later as
 # published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import os
 
 from ipaddress import ip_address
 from ipaddress import ip_network
 from netaddr import IPAddress
 from netaddr import IPRange
 from sys import exit
 
 from vyos.config import Config
 from vyos.template import render
 from vyos.utils.dict import dict_search
 from vyos.utils.process import call
 from vyos.utils.process import run
 from vyos.utils.network import is_subnet_connected
 from vyos.utils.network import is_addr_assigned
 from vyos import ConfigError
 from vyos import airbag
 airbag.enable()
 
 config_file = '/run/dhcp-server/dhcpd.conf'
 systemd_override = r'/run/systemd/system/isc-dhcp-server.service.d/10-override.conf'
 
 def dhcp_slice_range(exclude_list, range_dict):
     """
     This function is intended to slice a DHCP range. What does it mean?
 
     Lets assume we have a DHCP range from '192.0.2.1' to '192.0.2.100'
     but want to exclude address '192.0.2.74' and '192.0.2.75'. We will
     pass an input 'range_dict' in the format:
       {'start' : '192.0.2.1', 'stop' : '192.0.2.100' }
     and we will receive an output list of:
       [{'start' : '192.0.2.1' , 'stop' : '192.0.2.73'  },
        {'start' : '192.0.2.76', 'stop' : '192.0.2.100' }]
     The resulting list can then be used in turn to build the proper dhcpd
     configuration file.
     """
     output = []
     # exclude list must be sorted for this to work
     exclude_list = sorted(exclude_list)
     range_start = range_dict['start']
     range_stop = range_dict['stop']
     range_last_exclude = ''
 
     for e in exclude_list:
         if (ip_address(e) >= ip_address(range_start)) and \
            (ip_address(e) <= ip_address(range_stop)):
             range_last_exclude = e
 
     for e in exclude_list:
         if (ip_address(e) >= ip_address(range_start)) and \
            (ip_address(e) <= ip_address(range_stop)):
 
             # Build new address range ending one address before exclude address
             r = {
                 'start' : range_start,
                 'stop' : str(ip_address(e) -1)
             }
             # On the next run our address range will start one address after
             # the exclude address
             range_start = str(ip_address(e) + 1)
 
             # on subsequent exclude addresses we can not
             # append them to our output
             if not (ip_address(r['start']) > ip_address(r['stop'])):
                 # Everything is fine, add range to result
                 output.append(r)
 
             # Take care of last IP address range spanning from the last exclude
             # address (+1) to the end of the initial configured range
             if ip_address(e) == ip_address(range_last_exclude):
                 r = {
                   'start': str(ip_address(e) + 1),
                   'stop': str(range_stop)
                 }
                 if not (ip_address(r['start']) > ip_address(r['stop'])):
                     output.append(r)
         else:
           # if the excluded address was not part of the range, we simply return
           # the entire ranga again
           if not range_last_exclude:
               if range_dict not in output:
                   output.append(range_dict)
 
     return output
 
 def get_config(config=None):
     if config:
         conf = config
     else:
         conf = Config()
     base = ['service', 'dhcp-server']
     if not conf.exists(base):
         return None
 
     dhcp = conf.get_config_dict(base, key_mangling=('-', '_'),
                                 no_tag_node_value_mangle=True,
                                 get_first_key=True,
                                 with_recursive_defaults=True)
 
     if 'shared_network_name' in dhcp:
         for network, network_config in dhcp['shared_network_name'].items():
             if 'subnet' in network_config:
                 for subnet, subnet_config in network_config['subnet'].items():
                     # If exclude IP addresses are defined we need to slice them out of
                     # the defined ranges
                     if {'exclude', 'range'} <= set(subnet_config):
                         new_range_id = 0
                         new_range_dict = {}
                         for r, r_config in subnet_config['range'].items():
                             for slice in dhcp_slice_range(subnet_config['exclude'], r_config):
                                 new_range_dict.update({new_range_id : slice})
                                 new_range_id +=1
 
                         dhcp['shared_network_name'][network]['subnet'][subnet].update(
                                 {'range' : new_range_dict})
 
     return dhcp
 
 def verify(dhcp):
     # bail out early - looks like removal from running config
     if not dhcp or 'disable' in dhcp:
         return None
 
     # If DHCP is enabled we need one share-network
     if 'shared_network_name' not in dhcp:
         raise ConfigError('No DHCP shared networks configured.\n' \
                           'At least one DHCP shared network must be configured.')
 
     # Inspect shared-network/subnet
     listen_ok = False
     subnets = []
     failover_ok = False
     shared_networks =  len(dhcp['shared_network_name'])
     disabled_shared_networks = 0
 
 
     # A shared-network requires a subnet definition
     for network, network_config in dhcp['shared_network_name'].items():
         if 'disable' in network_config:
             disabled_shared_networks += 1
 
         if 'subnet' not in network_config:
             raise ConfigError(f'No subnets defined for {network}. At least one\n' \
                               'lease subnet must be configured.')
 
         for subnet, subnet_config in network_config['subnet'].items():
             # All delivered static routes require a next-hop to be set
             if 'static_route' in subnet_config:
                 for route, route_option in subnet_config['static_route'].items():
                     if 'next_hop' not in route_option:
                         raise ConfigError(f'DHCP static-route "{route}" requires router to be defined!')
 
             # DHCP failover needs at least one subnet that uses it
             if 'enable_failover' in subnet_config:
                 if 'failover' not in dhcp:
                     raise ConfigError(f'Can not enable failover for "{subnet}" in "{network}".\n' \
                                       'Failover is not configured globally!')
                 failover_ok = True
 
             # Check if DHCP address range is inside configured subnet declaration
             if 'range' in subnet_config:
                 networks = []
                 for range, range_config in subnet_config['range'].items():
                     if not {'start', 'stop'} <= set(range_config):
                         raise ConfigError(f'DHCP range "{range}" start and stop address must be defined!')
 
                     # Start/Stop address must be inside network
                     for key in ['start', 'stop']:
                         if ip_address(range_config[key]) not in ip_network(subnet):
                             raise ConfigError(f'DHCP range "{range}" {key} address not within shared-network "{network}, {subnet}"!')
 
                     # Stop address must be greater or equal to start address
                     if ip_address(range_config['stop']) < ip_address(range_config['start']):
                         raise ConfigError(f'DHCP range "{range}" stop address must be greater or equal\n' \
                                           'to the ranges start address!')
 
                     for network in networks:
                         start = range_config['start']
                         stop = range_config['stop']
                         if start in network:
                             raise ConfigError(f'Range "{range}" start address "{start}" already part of another range!')
                         if stop in network:
                             raise ConfigError(f'Range "{range}" stop address "{stop}" already part of another range!')
 
                     tmp = IPRange(range_config['start'], range_config['stop'])
                     networks.append(tmp)
 
             # Exclude addresses must be in bound
             if 'exclude' in subnet_config:
                 for exclude in subnet_config['exclude']:
                     if ip_address(exclude) not in ip_network(subnet):
                         raise ConfigError(f'Excluded IP address "{exclude}" not within shared-network "{network}, {subnet}"!')
 
             # At least one DHCP address range or static-mapping required
             if 'range' not in subnet_config and 'static_mapping' not in subnet_config:
                 raise ConfigError(f'No DHCP address range or active static-mapping configured\n' \
                                   f'within shared-network "{network}, {subnet}"!')
 
             if 'static_mapping' in subnet_config:
                 # Static mappings require just a MAC address (will use an IP from the dynamic pool if IP is not set)
+                used_ips = []
                 for mapping, mapping_config in subnet_config['static_mapping'].items():
                     if 'ip_address' in mapping_config:
                         if ip_address(mapping_config['ip_address']) not in ip_network(subnet):
                             raise ConfigError(f'Configured static lease address for mapping "{mapping}" is\n' \
                                               f'not within shared-network "{network}, {subnet}"!')
 
                         if 'mac_address' not in mapping_config:
                             raise ConfigError(f'MAC address required for static mapping "{mapping}"\n' \
                                               f'within shared-network "{network}, {subnet}"!')
 
+                        if mapping_config['ip_address'] in used_ips:
+                            raise ConfigError(f'Configured IP address for static mapping "{mapping}" exists on another static mapping')
+
+                        used_ips.append(mapping_config['ip_address'])
+
             # There must be one subnet connected to a listen interface.
             # This only counts if the network itself is not disabled!
             if 'disable' not in network_config:
                 if is_subnet_connected(subnet, primary=False):
                     listen_ok = True
 
             # Subnets must be non overlapping
             if subnet in subnets:
                 raise ConfigError(f'Configured subnets must be unique! Subnet "{subnet}"\n'
                                    'defined multiple times!')
             subnets.append(subnet)
 
             # Check for overlapping subnets
             net = ip_network(subnet)
             for n in subnets:
                 net2 = ip_network(n)
                 if (net != net2):
                     if net.overlaps(net2):
                         raise ConfigError(f'Conflicting subnet ranges: "{net}" overlaps "{net2}"!')
 
     # Prevent 'disable' for shared-network if only one network is configured
     if (shared_networks - disabled_shared_networks) < 1:
         raise ConfigError(f'At least one shared network must be active!')
 
     if 'failover' in dhcp:
         if not failover_ok:
             raise ConfigError('DHCP failover must be enabled for at least one subnet!')
 
         for key in ['name', 'remote', 'source_address', 'status']:
             if key not in dhcp['failover']:
                 tmp = key.replace('_', '-')
                 raise ConfigError(f'DHCP failover requires "{tmp}" to be specified!')
 
     for address in (dict_search('listen_address', dhcp) or []):
         if is_addr_assigned(address):
             listen_ok = True
             # no need to probe further networks, we have one that is valid
             continue
         else:
             raise ConfigError(f'listen-address "{address}" not configured on any interface')
 
 
     if not listen_ok:
         raise ConfigError('None of the configured subnets have an appropriate primary IP address on any\n'
                           'broadcast interface configured, nor was there an explicit listen-address\n'
                           'configured for serving DHCP relay packets!')
 
     return None
 
 def generate(dhcp):
     # bail out early - looks like removal from running config
     if not dhcp or 'disable' in dhcp:
         return None
 
     # Please see: https://vyos.dev/T1129 for quoting of the raw
     # parameters we can pass to ISC DHCPd
     tmp_file = '/tmp/dhcpd.conf'
     render(tmp_file, 'dhcp-server/dhcpd.conf.j2', dhcp,
            formater=lambda _: _.replace("&quot;", '"'))
     # XXX: as we have the ability for a user to pass in "raw" options via VyOS
     # CLI (see T3544) we now ask ISC dhcpd to test the newly rendered
     # configuration
     tmp = run(f'/usr/sbin/dhcpd -4 -q -t -cf {tmp_file}')
     if tmp > 0:
         if os.path.exists(tmp_file):
             os.unlink(tmp_file)
         raise ConfigError('Configuration file errors encountered - check your options!')
 
     # Now that we know that the newly rendered configuration is "good" we can
     # render the "real" configuration
     render(config_file, 'dhcp-server/dhcpd.conf.j2', dhcp,
            formater=lambda _: _.replace("&quot;", '"'))
     render(systemd_override, 'dhcp-server/10-override.conf.j2', dhcp)
 
     # Clean up configuration test file
     if os.path.exists(tmp_file):
         os.unlink(tmp_file)
 
     return None
 
 def apply(dhcp):
     call('systemctl daemon-reload')
     # bail out early - looks like removal from running config
     if not dhcp or 'disable' in dhcp:
         call('systemctl stop isc-dhcp-server.service')
         if os.path.exists(config_file):
             os.unlink(config_file)
 
         return None
 
     call('systemctl restart isc-dhcp-server.service')
     return None
 
 if __name__ == '__main__':
     try:
         c = get_config()
         verify(c)
         generate(c)
         apply(c)
     except ConfigError as e:
         print(e)
         exit(1)