Network Configuration / DHCP General Options Network Mask

Description

DHCP general option network mask is modified automatically when modifying the eth1 network configuration.

Context

IPBRICK network configuration is tightly connected to the DHCP and DNS services, so when modifying the network configuration at Advanced Configurations - IPBRICK - Definitions, one must expect that every service configuration should be adjusted automatically in accordance with the network modifications operated.

Meanwhile there is a known issue with the DHCP service so you are recommended to check, verify and if necessary adjust the specific configuration of your DHCP server.

Scenario

Here we present a known scenario (example) with the description of the issue detected:

• scenario before any modification
  • eth0
    • address: 192.168.130.1 / 24 (mask)
    • network: 192.168.130.0
    • broadcast: 192.168.130.255
  • eth1
    • address: 192.168.2.1 / 24 (mask)
    • network: 192.168.2.0
    • broadcast: 192.168.2.255
  • gateway
    • eth1
    • 192.168.2.254
  • DHCP - General Options
    • Network Mask: 255.255.255.0

Now we are going to modify the network configuration of the eth1 interface, this is exclusively the only modification that we will be doing:

• modifying eth1 and gateway
  • eth1
    • address: 72.29.87.114 / 29 (mask)
    • network: 72.29.87.112
    • broadcast: 72.29.87.119
  • gateway
    • eth1
    • 72.29.87.113

Now if you check the DHCP - General Options you will find that the Network Mask was modified automatically to "255.255.255.248".

Please adjust to the desired value of "255.255.255.0".

Solution

When modifying the network configuration of any network interface card (eth0, eth1, eth2, ...) please check and if necessary adjust the settings of the DHCP server.

Advanced Configurations - Support Services - DHCP - Subnets : General Options