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File Formats dhcp_network(4)
NAME
dhcp_network - DHCP network tables
DESCRIPTION
The Dynamic Host Configuration Protocol (DHCP) network
tables are used to map the client identifiers of DHCP
clients to IP addresses and the associated configuration
parameters of that address. One DHCP network table exists
for each network served by the DHCP server, and each table
is named using the network's IP address. There is no table
or file with the name dhcp_network.
The DHCP network tables can exist as ASCII text files,
binary text files, or NIS+ tables, depending on the data
store used. Since the format of the file could change, the
preferred method of managing the DHCP network tables is
through the use of dhcpmgr(1M) or the pntadm(1M) command.
The dhcp_network file is used as a policy mechanism for
whether in.dhcpd(1M) leases addresses on a given network. If
the DHCP server is not serving leases or information to a
network, there should be no dhcp_network file for that net-
work. To set the DHCP server in informational mode, where it
responds to INFORM messages but does not lease addresses on
that network, create an empty dhcp_network file for that
network. For normal operations, where the DHCP server both
leases addresses and responds to INFORM packets, create a
dhcp_network file using dhcpmgr(1M) or pntadm(1M) and popu-
late it with leasable addresses.
The format of the records in a DHCP network table depends on
the data store used to maintain the table. However, an entry
in a DHCP network table must contain the following fields:
Client_ID The client identifier field, Client_ID, is
an ASCII hexadecimal representation of the
unique octet string value of the DHCP Client
Identifier Option (code 61) which identifies
a DHCP client. In the absence of the DHCP
Client Identifier Option, the DHCP client is
identified using the form given below for
BOOTP clients. The number of characters in
this field must be an even number, with a
maximum length of 64 characters. Valid char-
acters are 0 - 9 and A-F. Entries with
values of 00 are freely available for
dynamic allocation to requesting clients.
BOOTP clients are identified by the concate-
nation of the network's hardware type (as
defined by RFC 1340, titled "Assigned
Numbers") and the client's hardware address.
For example, the following BOOTP client has
SunOS 5.10 Last change: 5 Mar 2004 1
File Formats dhcp_network(4)
a hardware type of '01' (10mb ethernet) and
a hardware address of 8:0:20:11:12:b7, so
its client identifier would be:
010800201112B7
Flags The Flags field is a decimal value, the bit
fields of which can have a combination of
the following values:
1 (PERMANENT)
Evaluation of the Lease field is turned
off (lease is permanent). If this bit is
not set, Evaluation of the Lease field
is enabled and the Lease is DYNAMIC.
2 (MANUAL)
This entry has a manual client ID bind-
ing (cannot be reclaimed by DHCP
server). Client will not be allocated
another address.
4 (UNUSABLE)
When set, this value means that either
through ICMP echo or client DECLINE,
this address has been found to be unus-
able. Can also be used by the network
administrator to prevent a certain
client from booting, if used in conjunc-
tion with the MANUAL flag.
8 (BOOTP)
This entry is reserved for allocation to
BOOTP clients only.
Client_IP The Client_IP field holds the IP address for
this entry. This value must be unique in the
SunOS 5.10 Last change: 5 Mar 2004 2
File Formats dhcp_network(4)
database.
Server_IP This field holds the IP address of the DHCP
server which owns this client IP address,
and thus is responsible for initial alloca-
tion to a requesting client. On a multi-
homed DHCP server, this IP address must be
the first address returned by
gethostbyname(3NSL).
Lease This numeric field holds the entry's abso-
lute lease expiration time, and is in
seconds since January 1, 1970. It can be
decimal, or hexadecimal (if 0x prefixes
number). The special value -1 is used to
denote a permanent lease.
Macro This ASCII text field contains the dhcptab
macro name used to look up this entry's con-
figuration parameters in the dhcptab(4)
database.
Comment This ASCII text field contains an optional
comment.
TREATISE ON LEASES
This section describes how the DHCP/BOOTP server calculates
a client's configuration lease using information contained
in the dhcptab(4) and DHCP network tables. The server con-
sults the LeaseTim and LeaseNeg symbols in the dhcptab, and
the Flags and Lease fields of the chosen IP address record
in the DHCP network table.
The server first examines the Flags field for the identified
DHCP network table record. If the PERMANENT flag is on, then
the client's lease is considered permanent.
If the PERMANENT flag is not on, the server checks if the
client's lease as represented by the Lease field in the net-
work table record has expired. If the lease is not expired,
the server checks if the client has requested a new lease.
If the LeaseNeg symbol has not been included in the client's
SunOS 5.10 Last change: 5 Mar 2004 3
File Formats dhcp_network(4)
dhcptab parameters, then the client's requested lease exten-
sion is ignored, and the lease is set to be the time remain-
ing as shown by the Lease field. If the LeaseNeg symbol has
been included, then the server will extend the client's
lease to the value it requested if this requested lease is
less than or equal to the current time plus the value of the
client's LeaseTim dhcptab parameter.
If the client's requested lease is greater than policy
allows (value of LeaseTim), then the client is given a lease
equal to the current time plus the value of LeaseTim. If
LeaseTim is not set, then the default LeaseTim value is one
hour.
For more information about the dhcptab symbols, see
dhcptab(4).
ATTRIBUTES
See attributes(5) for a description of the following attri-
bute:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWdhcsu |
|_____________________________|_____________________________|
| Interface Stability | Evolving |
|_____________________________|_____________________________|
SEE ALSO
dhcpconfig(1M), dhcpmgr(1M), dhtadm(1M), in.dhcpd(1M),
pntadm(1M), dhcptab(4), dhcp(5), dhcp_modules(5), attri-
butes(5)
Solaris DHCP Service Developer's Guide
System Administration Guide: IP Services
Reynolds, J. and J. Postel, Assigned Numbers, STD 2, RFC
1340, USC/Information Sciences Institute, July 1992.
SunOS 5.10 Last change: 5 Mar 2004 4
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This page was generated on Wed Sep 12 11:27:21 GMT 2007
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