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Function Specification
99
3.6.10.
DHCP Client
[Operating interface]
WAN interface
[Basic specifications]
It is based on RFC2131 and RFC2132. Moreover, it supports the DHCP relay function.
Supported messages are as follows.
Packet Direction
DHCP Message
Send
DISCOVER, REQUEST, RELEASE, DECLINE
Receive
OFFER, ACK
When the ACK message from DHCP server is received, ARP checks duplication of the distribution IP address.
The DHCP RELEASE message is sent when IP address distributed from the DHCP server overlaps with the LAN
interface IP address of this product. Afterwards, the DHCP sequence resumes.
[DHCP message transmission timing]
Transmission timing of RENEWING/REBINDING is as follows.
Extension Request
Timing
Destination
No. of
Transmissions
Description
RENEWING
Lease time×0.5
unicast
1
T1
unicast (resend) *
If the remaining time until T2 is at least 60 seconds, it is
sent by half.
REBINDING
Lease time×0.875
broadcast
1
T2
broadcast
(resend)
*
If the remaining time until lease time is at least 60
seconds, it is sent by half.
Transmission timing of DISCOVER message is as follows.
DISCOVER Transmission
Timing
Description
At DHCP startup
When there is no response 3 seconds after transmitting, it will be retransmitted.
Resending is repeated twice, and if there is still no response after 20 seconds, the
transmission will be redone.
(If there is no response, send in 3 seconds -> 3 seconds -> 23 seconds -> 3 seconds
-> 3 seconds ...)
When lease time expires
As with DHCP startup, when there is no response 3 seconds after transmitting, it will
be retransmitted.
Resending is repeated twice, and if there is still no response after 20 seconds, the
transmission will be redone.
(If there is no response, send in 3 seconds -> 3 seconds -> 23 seconds -> 3 seconds
-> 3 seconds ...)