# Subnet configuration

Supports multiple subnet with the DHCP server located on the MiVoice Office 400. The maximum number of subnets it can support is 100. DHCP Discover messages in a subnet are forwarded by a DHCP Relay (a service configured on the gateway of the subnet) to the DHCP server on MiVoice Office 400.

Table 1. DHCP multi-subnet support
Parameter | Explanation
Gateway | Gateway IP address of the subnet.
Subnet mask | 32-bit number that masks the IP address, and divides the IP address into network address and host address.
Enable |
Primary DNS server | Address of the primary DNS server (entry is read from the DNS server).
Secondary DNS server | Address of the secondary DNS server (entry is read from the DNS server).
First IP address | First address of the address range controlled by the DHCP server.
Last IP address | Last address of the address range controlled by the DHCP server.
Lease time | Time frame provided to the user to work with a certain IP address. Before the validity period expires, the DHCP clients (e.g. system phones) notify the DHCP server whether they want to maintain their link. Once the validity period has expired, the DHCP server extends the validity of all the links for which it received such requests and resets the timer for the validity period. All links for which no request was received are disconnected and the corresponding IP addresses are released.
Relay option | A DHCP Relay can be configured to add a Relay Agent Information (Option 82) into the forwarded DHCP Discover message. It is recommended that the same information is entered in the DHCP server. The option 82 string is entered in HEX format. A relay agent sends an option 82 (example: 01 0b 00 02 00 16 45 53 2d 34 31 32 34). This string is entered in the subnet settings without spaces (example. 010b0002001645532d34313234) For a subnet, if the MiVoice Office 400 DHCP server has the DHCP Relay Option configured and now receives a DHCP Discover message without option 82 or with a wrong option 82, then it ignores the DHCP Discover and doesn’t send an “Offer” back

Parent topic: DHCP server
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