Check-Mac-Address

These scenarios show how the check-mac-address feature works for the DHCP server

../../../_images/check-mac-address.svg

Test Check MAC Address

Description

The check-mac-address option filters packets if there are differences between the MAC address found at the ethernet header and the MAC address found in the DHCP packet. To check this option, you should send packets with these differences and enable this option to see if warnings appear in your logs. Also, this test checks how the server behaves under normal conditions.

Scenario

Step 1: Set the following configuration in DUT0 :

set interfaces ethernet eth0 address 10.0.0.1/24
set service dhcp-server shared-network dhcp subnet 10.0.0.0/24 start 10.0.0.5 stop 10.0.0.5
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 2: Run the command system journal show | tail on DUT0 and check whether the output contains the following tokens:

DHCPDISCOVER from 10:00:00:00:00:02 via eth0
Show output
May 19 17:46:27.246039 osdx dhcpd[711263]: Wrote 0 leases to leases file.
May 19 17:46:27.291741 osdx dhcpd[711263]: Server starting service.
May 19 17:46:27.406538 osdx cfgd[1918]: [673163]Completed change to active configuration
May 19 17:46:27.407056 osdx OSDxCLI[673163]: User 'admin' committed the configuration.
May 19 17:46:27.429904 osdx OSDxCLI[673163]: User 'admin' left the configuration menu.
May 19 17:46:27.564205 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal show | tail'.
May 19 17:46:28.169251 osdx dhcpd[711263]: DHCPDISCOVER from 10:00:00:00:00:02 via eth0
May 19 17:46:29.169841 osdx dhcpd[711263]: DHCPOFFER on 10.0.0.5 to 10:00:00:00:00:02 via eth0
May 19 17:46:29.208893 osdx dhcpd[711263]: DHCPDISCOVER from 10:00:00:00:00:02 via eth0
May 19 17:46:29.208929 osdx dhcpd[711263]: DHCPOFFER on 10.0.0.5 to 10:00:00:00:00:02 via eth0

Step 3: Modify the following configuration lines in DUT0 :

set service dhcp-server check-mac-address

Step 4: Run the command system journal clear on DUT0.

Step 5: Run the command system journal show | tail on DUT0 and check whether the output does not contain the following tokens:

DHCPDISCOVER from 10:00:00:00:00:02 via eth0
Show output
May 19 17:46:30.244883 osdx systemd-journald[505760]: Runtime Journal (/run/log/journal/d1b141b298644f3ea5560bad25bf4943) is 1.8M, max 13.8M, 11.9M free.
May 19 17:46:30.247596 osdx systemd-journald[505760]: Received client request to rotate journal, rotating.
May 19 17:46:30.247634 osdx systemd-journald[505760]: Vacuuming done, freed 0B of archived journals from /run/log/journal/d1b141b298644f3ea5560bad25bf4943.
May 19 17:46:30.253968 osdx dhcpd[711335]: MAC received in DHCP packet (10:00:00:00:00:02) is different than source MAC in ethernet header (10:00:00:00:00:01)
May 19 17:46:30.254601 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal clear'.

Step 6: Run the command system journal show | tail on DUT0 and check whether the output contains the following tokens:

MAC received in DHCP packet (10:00:00:00:00:02) is different than source MAC in ethernet header (10:00:00:00:00:01)
Show output
May 19 17:46:30.244883 osdx systemd-journald[505760]: Runtime Journal (/run/log/journal/d1b141b298644f3ea5560bad25bf4943) is 1.8M, max 13.8M, 11.9M free.
May 19 17:46:30.247596 osdx systemd-journald[505760]: Received client request to rotate journal, rotating.
May 19 17:46:30.247634 osdx systemd-journald[505760]: Vacuuming done, freed 0B of archived journals from /run/log/journal/d1b141b298644f3ea5560bad25bf4943.
May 19 17:46:30.253968 osdx dhcpd[711335]: MAC received in DHCP packet (10:00:00:00:00:02) is different than source MAC in ethernet header (10:00:00:00:00:01)
May 19 17:46:30.254601 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal clear'.
May 19 17:46:30.313250 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal show | tail'.

Step 7: Set the following configuration in DUT1 :

set interfaces ethernet eth0 mac '10:00:00:00:00:05'
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 8: Modify the following configuration lines in DUT1 :

set interfaces ethernet eth0 address dhcp

Step 9: Run the command interfaces ethernet eth0 show on DUT1 and check whether the output contains the following tokens:

10.0.0.5
Show output
-----------------------------------------------------------------
Name           IP Address           Admin  Oper  Vrf  Description
-----------------------------------------------------------------
eth0  10.0.0.5/24                   up     up
      fe80::dcad:beff:feef:6c10/64

Step 10: Run the command service dhcp-server show leases main | grep 10.0.0.5 on DUT0 and check whether the output contains the following tokens:

10:00:00:00:00:05
Show output
10.0.0.5   10:00:00:00:00:05  2026/05/19 17:46:32  2026/05/20 05:46:32  2026/05/19 17:46:32

Test Check MAC Address VRF

Description

This scenario configures a DHCP server with VRF instead of regular interfaces and checks the check-mac-address option. To check this option, you will need to send packets with differences in the Source MAC for the link layer and the client MAC from the application layer.

Scenario

Step 1: Set the following configuration in DUT0 :

set interfaces ethernet eth0 address 10.0.0.1/24
set interfaces ethernet eth0 vrf VRF0
set service dhcp-server shared-network dhcp local-vrf VRF0
set service dhcp-server shared-network dhcp subnet 10.0.0.0/24 start 10.0.0.5 stop 10.0.0.6
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'
set system vrf VRF0

Step 2: Run the command system journal show | tail on DUT0 and check whether the output contains the following tokens:

DHCPDISCOVER from 10:00:00:00:00:02 via eth0
Show output
May 19 17:46:39.436660 osdx dhcpd[711739]: Wrote 0 leases to leases file.
May 19 17:46:39.465758 osdx dhcpd[711739]: Server starting service.
May 19 17:46:39.623407 osdx cfgd[1918]: [673163]Completed change to active configuration
May 19 17:46:39.624137 osdx OSDxCLI[673163]: User 'admin' committed the configuration.
May 19 17:46:39.646391 osdx OSDxCLI[673163]: User 'admin' left the configuration menu.
May 19 17:46:39.780648 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal show | tail'.
May 19 17:46:40.070870 osdx dhcpd[711739]: DHCPDISCOVER from 10:00:00:00:00:02 via eth0
May 19 17:46:41.071905 osdx dhcpd[711739]: DHCPOFFER on 10.0.0.5 to 10:00:00:00:00:02 via eth0
May 19 17:46:41.118255 osdx dhcpd[711739]: DHCPDISCOVER from 10:00:00:00:00:02 via eth0
May 19 17:46:41.118286 osdx dhcpd[711739]: DHCPOFFER on 10.0.0.5 to 10:00:00:00:00:02 via eth0

Step 3: Modify the following configuration lines in DUT0 :

set service dhcp-server check-mac-address

Step 4: Run the command system journal clear on DUT0.

Step 5: Run the command system journal show | tail on DUT0 and check whether the output does not contain the following tokens:

DHCPDISCOVER from 10:00:00:00:00:02 via eth0
Show output
May 19 17:46:42.460318 osdx systemd-journald[505760]: Runtime Journal (/run/log/journal/d1b141b298644f3ea5560bad25bf4943) is 1.8M, max 13.8M, 11.9M free.
May 19 17:46:42.461656 osdx systemd-journald[505760]: Received client request to rotate journal, rotating.
May 19 17:46:42.461702 osdx systemd-journald[505760]: Vacuuming done, freed 0B of archived journals from /run/log/journal/d1b141b298644f3ea5560bad25bf4943.
May 19 17:46:42.469172 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal clear'.

Step 6: Run the command system journal show | tail on DUT0 and check whether the output contains the following tokens:

MAC received in DHCP packet (10:00:00:00:00:02) is different than source MAC in ethernet header (10:00:00:00:00:01)
Show output
May 19 17:46:42.460318 osdx systemd-journald[505760]: Runtime Journal (/run/log/journal/d1b141b298644f3ea5560bad25bf4943) is 1.8M, max 13.8M, 11.9M free.
May 19 17:46:42.461656 osdx systemd-journald[505760]: Received client request to rotate journal, rotating.
May 19 17:46:42.461702 osdx systemd-journald[505760]: Vacuuming done, freed 0B of archived journals from /run/log/journal/d1b141b298644f3ea5560bad25bf4943.
May 19 17:46:42.469172 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal clear'.
May 19 17:46:42.527277 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal show | tail'.
May 19 17:46:42.628064 osdx OSDxCLI[673163]: User 'admin' executed a new command: 'system journal show | tail'.
May 19 17:46:43.201873 osdx dhcpd[711811]: MAC received in DHCP packet (10:00:00:00:00:02) is different than source MAC in ethernet header (10:00:00:00:00:01)
May 19 17:46:44.246625 osdx dhcpd[711811]: MAC received in DHCP packet (10:00:00:00:00:02) is different than source MAC in ethernet header (10:00:00:00:00:01)

Step 7: Set the following configuration in DUT1 :

set interfaces ethernet eth0 mac '10:00:00:00:00:05'
set system login user admin authentication encrypted-password '$6$GSjsCj8gHLv$/VcqU6FLi6CT2Oxn0MJQ2C2tqnRDrYKNF8HIYWJp68nvXvPdFccDsT04.WtigUONbKYrgKg8d6rEs8PjljMkH0'

Step 8: Modify the following configuration lines in DUT1 :

set interfaces ethernet eth0 address dhcp

Step 9: Run the command interfaces ethernet eth0 show on DUT1 and check whether the output contains the following tokens:

10.0.0.5
Show output
-----------------------------------------------------------------
Name           IP Address           Admin  Oper  Vrf  Description
-----------------------------------------------------------------
eth0  10.0.0.5/24                   up     up
      fe80::dcad:beff:feef:6c10/64

Step 10: Run the command service dhcp-server show leases VRF0 | grep 10.0.0.5 on DUT0 and check whether the output contains the following tokens:

10:00:00:00:00:05
Show output
10.0.0.5   10:00:00:00:00:05  2026/05/19 17:46:46  2026/05/20 05:46:46  2026/05/19 17:46:46