HP V1910 Switch Series User Manual

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When the half lease duration elapses, the DHCP client sends to the DHCP server a DHCP-REQUEST
unicast to extend the lease duration. Upon availability of the IP address, the DHCP server returns a
DHCP-ACK unicast confirming that the client’s lease duration has been extended, or a DHCP-NAK
unicast denying the request.
If the client receives no reply, it will broadcast another DHCP-REQUEST message for lease extension after
7/8 lease duration elapses. The DHCP server will handle the request as above mentioned.
DHCP message format
Figure 234 gives the DHCP message format, which is based on the BOOTP message format and involves
eight types. These types of messages have the same format except that some fields have different values.
The numbers in parentheses indicate the size of each field in bytes.
Figure 234 DHCP message format
op (1)
0715
htype (1) hlen (1) hops (1)
xid (4)
23 31
secs (2) flags (2)
ciaddr (4)
yiaddr (4)
siaddr (4)
giaddr (4)
chaddr (16)
sname (64)
file (128)
options (variable)
 op: Message type defined in option field. 1 = REQUEST, 2 = REPLY
 htype, hlen: Hardware address type and length of a DHCP client.
 hops: Number of relay agents a request message traveled.
 xid: Transaction ID, a random number chosen by the client to identify an IP address allocation.
 secs: Filled in by the client, the number of seconds elapsed since the client began address
acquisition or renewal process. This field is reserved and set to 0.
 flags: The leftmost bit is defined as the BROADCAST (B) flag. If this flag is set to 0, the DHCP server
sent a reply back by unicast; if this flag is set to 1, the DHCP server sent a reply back by broadcast.
The remaining bits of the flags field are reserved for future use.
 ciaddr: Client IP address.
 yiaddr: 'your' (client) IP address, assigned by the server.
 siaddr: Server IP address, from which the clients obtained configuration parameters.
 giaddr: IP address of the first relay agent a request message traveled.
 chaddr: Client hardware address.
 sname: Server host name, from which the client obtained configuration parameters.
 file: Bootfile name and path information, defined by the server to the client.

HP V1910 Switch Series Specifications

General

Brand	HP
Model	V1910 Switch Series
Category	Switch
Language	English