bootpd(1M)

NAME

bootpd — Internet Boot Protocol server

SYNOPSIS

/usr/lbin/bootpd [-d debuglevel] [-p ping-timeout] [-t timeout] [-P] [configfile [dumpfile]]

DESCRIPTION

The bootpd daemon implements three functions: a Dynamic Host Configuration Protocol (DHCP) server as defined in RFC1541, an Internet Boot Protocol (BOOTP) server as defined in RFC951 and RFC1395, and a DHCP/BOOTP relay agent as defined in RFC1542. It also contains some of the useful fields as defined in RFC2132.

bootpd is run through inetd (see inetd(1M)). It is run by /etc/inetd when the following line (or equivalent) is included in the file /etc/inetd.conf:

bootps dgram udp wait root /usr/lbin/bootpd bootpd 

bootpd starts when a boot request arrives. If it has not received another boot request after 500 minutes, bootpd exits. The -t option can be used to specify a different timeout value in minutes (such as -t20). With a timeout value of zero (-t0), bootpd never exits.

The -d option sets the verbosity level (1-3) of the logging emitted by the daemon via syslog (see syslog(3C)). For improved performance, this option should not be used. If this option is not used, no logging is done by syslog except for fatal errors.

By default, the bootpd daemon pings the IP address before assigning the address to a client to check if the IP Address is already in use. The -P option suppresses bootpd from pinging this address.

The -p option can be used to specify the ping timeout period. The server pings for this duration of time to check if the IP address is already in use. The ping-timeout period is specified in milliseconds and the maximum value is 3000 milliseconds. When the -P option is used, the -p option has no effect, since bootpd never pings the IP address.

When bootpd receives a DHCP/BOOTP request, it first checks if the hardware address of the client is listed in the /etc/dhcpdeny database. If yes, this client is denied lease. If the client is not listed in the dhcpdeny database, it checks whether the client information is in the /etc/bootptab database. If the client information is available, bootpd sends back the reply. Otherwise, it checks whether there is any matched relay information for the client in the /etc/bootptab database. If so, bootpd goes through a series of checks to see if it should relay the request. If no matched relay information was found, bootpd checks whether the client information is matched by a pool or device group in the /etc/dhcptab database. If a match is found, bootpd sends back a reply. The request is dropped if no matched group information is found.

To reply to a DHCP or BOOTP request the server puts together a BOOTREPLY message and does a number of checks to ensure the message is sent to the correct destination.

bootpd first checks the ciaddr (client IP address) field of the DHCP/BOOTP packet. If this field is nonzero, the BOOTREPLY message is sent to the IP address identified in ciaddr.

If the ciaddr field is zero, bootpd checks the giaddr field. If this field is not zero, bootpd sends the BOOTREPLY message to the relay agent specified in giaddr field and the relay agent delivers the BOOTREPLY message to the client. If the giaddr field is zero, bootpd sends the BOOTREPLY message to the client. In both cases, the BOOTREPLY will either be sent to the IP address specified in the yiaddr (your IP address) field or as a broadcast message. On HP-UX, there are two ways to specify that the BOOTREPLY should be sent as a broadcast message.

1.: The client sets the broadcast flag bit in the flag field (bit 0) of the DHCP/BOOTP request packet.
2.: Define the ba tag in the bootptab file (see Tags for client entries below)

For the case where the bootpd has matched a relay entry in /etc/bootptab, it attempts to forward the request to the configured DHCP/BOOTP server.

bootpd first checks whether the relay function is enabled for the requesting client. The relay capability is configurable. If the relay function is disabled, then the request packet is dropped.

Before bootpd relays the request, it also examines the giaddr (gateway IP address) field. The client sets the giaddr field to zero when it sends out the request. If the relay agent finds this field is zero, it fills this field with the primary IP address of the interface on which the request was received; otherwise, the relay agent does not change this field. Then bootpd increments the value of the hops field, and relays the request to the DHCP/BOOTP servers that have been configured for this client.

If the relay function is enabled for this client, bootpd checks the hops field of the DHCP/BOOTP request packet. The client sets the hops field to 0 when it sends out the DHCP/BOOTP request. The hops value is increased every time the request packet is relayed by a relay agent. The maximum hop number can be configured. The maximum possible hop number allowed is 16. The default maximum is set to 4. The request packet is dropped if the hop value exceeds the configured maximum.

Then bootpd compares the value of the secs (seconds since the client began booting) field of the DHCP/BOOTP packet to the threshold value. The client sets the secs field to zero when it first sends out the request. The client repeats the request if it does not receive a reply. When the client repeats the request, it sets the secs value to the number of seconds since the first request was sent. bootpd does not relay the request if the value of the secs field is less than the threshold value. The threshold value can be configured. The default value is 0.

Configuration

Upon startup, bootpd reads its configuration files to build its internal database, then listens for boot request packets. The default configuration files are /etc/dhcpdeny, /etc/bootptab, and /etc/dhcptab. The bootptab file can be specified in the command line. bootpd rereads its configuration file when it receives a hangup signal, SIGHUP, or when it receives a boot request packet and detects that the configuration file has been updated. If hosts are added, deleted, or modified, their entries in the bootpd internal database are updated accordingly when the configuration files are reread. The /etc/dhcpdeny database contains the list of hardware addresses of the clients that will not be served by this server.

If bootpd receives a SIGUSR1 signal, it dumps its memory-resident database to the file /var/tmp/bootpd.dump or the dumpfile specified in the command line.

The configuration file can contain two types of host entries:

1.: The client entries, which contains the client information.
2.: The relay entries, which contains the configuration to relay DHCP/BOOTP requests for one or more clients.

The configuration uses two-character, case-sensitive tag symbols to represent host parameters. These parameter declarations are separated by colons (:). The general format is:

hostname:tg=value :...: tg=value :...: tg=value :...

where hostname is the actual name of a DHCP/BOOTP client in the client entries, and in the case of a relay entry, it can be the actual name of a client if it is an individual relay entry, or it can be a name for a group of clients if it is a group relay entry. tg is a two-character tag symbol. Most tags must be followed by an equals-sign, and a value as above. Some can appear in a boolean form with no value (that is, :tg:).

Blank lines and lines beginning with # are ignored in the configuration file. Host entries are separated from one another by newlines; a single host entry can be extended over multiple lines if the lines end with a backslash (\). It is also acceptable for lines to be longer than 80 characters. Tags can appear in any order with the following exceptions: The host name must be the very first field in an entry, and the hardware type tag, ht, must precede the hardware address tag, ha. and the hardware mask tag, hm.

IP addresses are specified in standard Internet dot notation, and can use decimal, octal, or hexadecimal numbers (octal numbers begin with 0, hexadecimal numbers begin with 0x or 0X). Certain tags accept a list of one or more IP addresses (ip_address_list). When more than one IP address is listed, the addresses must be separated by whitespace.

The types of tags can be grouped into three categories:

1.: The tags that can be used for both the client and the relay entries.
2.: The tags that can only be used in the relay entries.
3.: The tags that can only be used in the client information entries.

Tag ip is used to differentiate a client entry from a relay entry. An entry with tag ip defined is treated as a client entry. A relay entry can contain the relay configuration for an individual client, also a hardware address mask mechanism is provided to configure the relay entry for a group of clients. The group client relay entries are kept in a linear sorted table by bootpd. When a client does not have an individual relay specification, the linear table is searched to see if there is a match for the client. If there are multiple matched entries in the sorted table, only the first one is used. Tag hm is used to differentiate an individual client relay entry from a group relay entry. The linear sorted table is sorted on the value of tag hm. The search and match mechanism is explained in the discussion of tag hm.

Tags for both kinds of entries

ha=hardware-address

This tag specifies the hardware address of the client. The hardware address must be specified in hexadecimal; optional periods and/or a leading 0x can be included for readability. The ha tag must be preceded by the ht tag (either explicitly or implicitly; see tc below).

ht=hardware-type

This tag specifies the hardware type code. hardware-type can be an unsigned decimal, octal, or hexadecimal integer corresponding to one of the ARP Hardware Type codes specified in RFC1010. It can also be specified by the symbolic names ethernet or ether for 10-Mb Ethernet; ethernet3 or ether3 for 3-Mb experimental Ethernet; ieee802, tr, or token-ring for IEEE 802 networks; pronet for Proteon ProNET Token Ring; chaos, and arcnet, for Chaos and ARCNET, respectively.

tc=template-host

This tag indicates a table continuation. Often, many host entries share common values for certain tags (such as domain servers, etc.). Rather than repeatedly specifying these tags, a full specification can be listed for one host entry and shared by others via the tc mechanism.

The template-host is a dummy host that does not actually exist and never sends boot requests. Information explicitly specified for a host always overrides information implied by a tc tag symbol. The value of template-host can be the host name or IP address of any host entry previously listed in the configuration file.

Sometimes it is necessary to delete a specific tag after it has been inferred via tc. This can be done using the construction tag@ which removes the effect of tag. For example, to completely undo an RFC1034 domain name server specification, use :ds@: at an appropriate place in the configuration entry. After removal with @, a tag is eligible to be set again through the tc mechanism.

Tags for relay entries

bp=bootp-servers: This tag specifies the BOOTP servers that DHCP/BOOTP requests will be relayed to. The value of bootp-servers can be one or more individual IP addresses, and/or one or more network broadcast addresses. A relay entry with this tag configured indicates that the relay function is on for the clients specified in this entry. A relay entry missing this symbol means that the relay function is off for the clients specified in this entry.
th=threshold: This tag specifies the threshold value in seconds for the entry. The default value is 0.
hp=hops: This tag specifies the maximum hops value. If the hops value exceeds 16, it is set to 16. The default value is 4.
hm=hardware-address-mask: This tag specifies the mask for the hardware address ha. hardware-address-mask must be specified in hexadecimal. An optional leading 0x can be included for readability. The hm tag must be preceded by the ht tag (either explicitly or implicitly; see tc above). Each 0 bit in hm specifies that the corresponding bit in ha is a "don't-care" bit, each 1 bit in hm specifies that the corresponding bit in the ha value is ANDed with the hm value. If the result is the same and also the hardware type matches, then a match is found. For example,
if (((hm & ha)==(client_hw_addr & hm)) && (ht == client_hw_type)) then a match is found else continue the search

Tags for client entries

ba

This tag specifies that bootpd should broadcast the boot reply to the client. As a boolean tag, it causes bootpd to send the boot reply on the configured broadcast address of each network interface. You can also assign the tag an IP-address value, which specifies the specific IP or broadcast address for the boot reply.

bf=filename

This tag specifies the filename of the bootfile that the client should download. The client's boot request, and the values of the hd (see below) and bf symbols, determine the contents of the bootfile field in the boot reply packet.

If the client specifies an absolute path name (in its boot request), and that file is accessible on the server machine (see below), bootpd returns that path name in the reply packet. If the file is not accessible, the request is discarded; no reply is sent. If the client specifies a relative path name, bootpd constructs a full path name by appending the relative path name to the value of the hd tag, and tests to determine if the full path name is accessible. If the full path name is accessible, it is returned in the boot reply packet; if not, the request is discarded.

Clients that do not specify boot files in their boot requests always elicit a reply from the server. The exact reply depends on the values of the hd and bf tags. If the bf tag specifies an absolute path name, and the file is accessible, that path name is returned in the reply packet. Otherwise, if the hd and bf tags together specify an accessible file, that file name is returned in the reply. If a complete file name cannot be determined, or the file is not accessible publicly, the reply contains a zeroed-out bootfile field.

If the tftp pseudo-user exists, bootpd treats all path names (absolute or relative) as being relative to the home directory of tftp and checks there first. If the file is not accessible under the tftp home directory or the tftp pseudo-user does not exist, bootpd checks for the file relative to /.

For a file to be available, it must exist, and be publicly readable.

All file names are first tried as filename.hostname and then simply as filename. However, in the case when the tftp pseudo-user exists, but filename.hostname and filename are not accessible under the tftp home directly, only filename is checked relative to /.

Note that a file considered to be accessible relative to / might not actually be accessible via tftp if the command line arguments to tftpd disallow that path.

bs=size

This tag specifies the size of the bootfile. The parameter size can be either a decimal, octal, or hexadecimal integer specifying the size of the bootfile in 512-octet blocks, or the keyword auto, which causes the server to automatically calculate the bootfile size at each request. Specifying the bs symbol as a boolean has the same effect as specifying auto as its value.

ci=client_ID

This tag specifies the client identifier of the client. The parameter client_ID can be either a hexadecimal integer, or a string contained in double quotes. The client_ID is a unique identifier that the DHCP client may use to identify itself to the server. If present, the client identifier supersedes the hardware address, so a client and an entry will only match in one of two situations: one, they both have the same client identifier, or two they both have the same hardware address and neither has a client identifier. If a request has a client identifier, then that is used to match the client up with an entry in the bootp configuration file. One common client ID used is to concatenate the hardware type (e.g. 0x01 for ethernet) with the hardware address.

cs=ip_address_list

This tag specifies the IP addresses of RFC865 Quote of the Day (cookie) servers.

dn=domain_name

This tag specifies the domain name of the client for Domain Name Server resolution (see RFC1034).

ds=ip_address_list

This tag specifies the IP addresses of RFC1034 Domain Name servers.

ef=filename

Specifies the name of an extensions file. The file, retrievable via TFTP, contains information which can be interpreted in the same way as the 64-octet vendor-extension field within the BOOTP response. The maximum length of the file is unconstrained. All references to an extensions filename within the file are ignored.

gw=ip_address_list

This tag specifies the IP addresses of gateways for the client's subnet. If one of multiple gateways is preferred, it should be listed first.

hd=home-directory

This tag specifies a directory name to which the bootfile is appended (see the bf tag above). The default value of the hd tag is /.

hn

The presence of this tag indicates that the client's host name should be sent in the boot reply. The hn tag is a boolean tag. bootpd attempts to send the entire host name as it is specified in the configuration file or hosts database. The configuration file is checked first, if the host name is not found, the hosts(4) database is then checked. If the hostname cannot fit into the reply packet, an attempt is made to shorten the name to just the host field (up to the first period, if present) and then tried. In no case is an arbitrarily truncated host name sent. If nothing reasonable can fit, nothing is sent.

im=ip_address_list

This tag specifies the IP addresses of Impress network image servers.

ip=ip-address

This tag specifies the IP address of the DHCP/BOOTP client.

lg=ip_address_list

This tag specifies the IP addresses of MIT-LCS UDP log servers.

lp=ip_address_list

This tag specifies the IP addresses of Berkeley 4BSD printer servers.

md=merit_dump_file

This tag specifies the name of a file to dump the core of a client.

ms=ip_address_list

This tag specifies the IP address(es) of SMTP servers available to the client (RFC2132).

na=ip_address_list

This tag specifies the IP address(es) of RFC 1001/1002 NetBIOS name server(s) in order of preference.

nb=ip_address_list

This tag specifies the IP address(es) of RFC 1001/1002 NetBIOS datagram distribution server(s) in order of preference.

nc=NetBIOS_node_type

Specifies the NetBIOS node type code. Allows NetBIOS over TCP/IP clients to be configured as described in RFC1001/1002. The NetBIOS_node_type can be an unsigned decimal, octal, or hexadecimal integer corresponding to one of the client types as follows:

0x1 or B-node for B-node;
0x2 or P-node for P-node;
0x4 or M-node for M-node;
0x8 or H-node for H-node.

nd=string

This tag specifies the NetBIOS over TCP/IP scope parameter for the client as specified in RFC 1001/1002.

ns=ip_address_list

This tag specifies the IP addresses of IEN-116 name servers.

nt=ip_address_list

This tag specifies the IP addresses of Network Time Protocol servers. Servers should be listed in order of preference.

pd=NIS+-domain-name

This tag specifies the name of clients NIS+ domain name (RFC2132).

ps=ip_address_list

This tag specifies the IP address(es) of NIS+ servers available to the client (RFC2132).

rl=ip_address_list

This tag specifies the IP addresses of RFC887 Resource Location Protocol servers.

rp=root_path

This tag specifies a path name to be mounted as a root disk.

sa=tftp_server

This tag specifies the IP address of the TFTP server where the client's bootfile resides. When this option is enabled, bootpd uses the IP address specified in this tag for the siaddr field in a BOOTP/DHCP packet header. Otherwise, the IP address of the BOOTP/DHCP server is used in the siaddr field. The sa tag allows the BOOTP/DHCP server and the TFTP server to be two different systems, if desired.

sm=subnet-mask

This tag specifies the client's subnet mask. subnet-mask is specified as a single IP address.

sr=destination_ip_address gateway_ip_address ...

This tag specifies a list of static routes that the client should put in its routing cache. Each route consists of a pair of IP addresses. The first address is the destination address, and the second is the router. Use the gw= option to specify the default route (0.0.0.0) as it is not a legal destination address.

ss=ip_address

This tag specifies the IP address of a swap server.

Tnnn=generic-data

This is a generic tag where nnn is an RFC1533 option field tag number. Use this option to configure RFC1533 options not currently supported with bootpd tag names. This option allows one to immediately take advantage of future extensions to RFC1533. The generic-data data can be represented as either a stream of hexadecimal numbers or as a quoted string of ASCII characters. The length of the generic data is automatically determined and inserted into the proper fields of the RFC1541-style boot reply.

to=offset

This tag specifies the client's time zone offset in seconds from UTC. The time offset can be either a signed decimal integer or the keyword auto which uses the server's time zone offset. Specifying the to symbol as a boolean has the same effect as specifying auto as its value.

ts=ip_address_list

This tag specifies the IP addresses of RFC868 Time Protocol servers.

yd=NIS-domain-name

Specifies the name of the client's NIS domain.

ys=ip_address_list

Specifies the IP address(es) of NIS servers available to the client. Servers should be listed in order of preference.

vm=magic-cookie

This tag specifies the RFC1048 vendor information magic cookie. magic-cookie can be one of the following keywords: auto (indicating that vendor information is determined by the client's request), rfc1048 (which always forces an RFC1048-style reply), or cmu (which always forces a CMU-style reply).

Vnnn=generic-data

This is a generic tag for vendor specific information where nnn is a vendor defined option field tag number. The generic-data data can be represented as either a stream of hexadecimal numbers or as a quoted string of ASCII characters. The length of the generic data is automatically determined and inserted into the vendor specific field of the RFC1541-style boot reply.

xd=ip_address_list

This tag specifies the IP addresses of systems that are running the X Window System Display Manager and are available to the client. Addresses should be listed in order of preference.

xf=ip_address_list

This tag specifies the IP addresses of X window System font servers available to the client. Servers should be listed in order of preference.

Dhcpdeny Configuration

The configuration file /etc/dhcpdeny contains the list of hardware addresses, one address per line, for clients that will not be served by our server. If we know about some bad clients in the network and we don't want to serve them, add the hardware address of those clients in this file. This file, like other configuration files, takes # character as the starting of a comment.

Dhcptab Configuration

The configuration file /etc/dhcptab defines groups of IP addresses that to be leased out to clients. It also specifies certain general behaviors of the server, such as whether or not to give addresses from these groups to bootp clients or only to DHCP clients.

The configuration file has a format similar to the /etc/bootptab configuration file, with a keyword followed by one or more tag symbols. These tag symbols are separated by colons (:). The general format is:

keyword:tg=value :...:tg=value :...: tg=value :...

where keyword is one of four allowed (non-case-sensitive) symbols and tg is a two or more (case-sensitive) character tag symbol. Most tags must be followed by an equals-sign and a value as above. Some can also appear in a boolean form with no value (i.e. :tg:).

Blank lines and lines beginning with # are ignored in the configuration file. Keyword entries are separated from one another by newlines; a single host entry may be extended over multiple lines if each continued line ends with a backslash (\). Lines may be longer than 80 characters. Tags can appear in any order.

IP addresses must be specified in standard Internet ``dot'' notation, and can use decimal, octal, or hexadecimal numbers (octal numbers begin with 0, hexadecimal numbers begin with 0x or 0X). Certain tags accept a list of one or more IP addresses (ip_address_list). When more than one IP address is listed, they must be separated by white space.

The currently recognized keywords are:

dhcp_pool_group: This keyword is followed by tags defining a group of IP addresses to give out to clients on the same subnet, and the characteristics of that group. In addition to the tags defined for DHCP groups, all of the two-letter tags for bootp entries may also be used (except for ht, the hardware type tag, ha, the hardware address tag, or ci, the client ID tag. Required tags are: subnet-mask, addr-pool-start-address, and addr-pool-last-address.
dhcp_device_group: This keyword is used to define a group of IP addresses on a subnet much like dhcp_pool_group, but with one exception: all clients in a device group must have the same client class (specified with tag class-id). This allows different types of clients to receive different parameters from the server. Required tags are: class-id, subnet-mask, addr-pool-start-address, and addr-pool-last-address.
dhcp_default_client_settings: This keyword is followed by tags to be applied to all groups. These tag values can be overridden for a specific group if that tag is defined for that specific group. This keyword simply saves one from entering the same tag for every group. Thus most tags that may be used for dhcp_pool_group, and dhcp_device_group, may be used here. The tag descriptions specify if a tag may not be used here.
dhcp_server_settings: This keyword is followed by tags that specify a few general behaviors for the dhcp server as a whole.

The currently supported tags for dhcp_server_settings are:

allow-subnet-selection

This boolean tag specifies that bootpd supports the subnet selection option (RFC 3011). However, a group will support the subnet selection option only when this tag is specified in that group.

dhcpdb-write-perf=

This parameter takes a small integer (like 2 or 5) as input. If set, the write to the /etc/dhcpdb file will be delayed by the server. This will increase performance for busy servers. If set to a value greater than 2, the server will spawn a new process to do the writing, which will be a considerable performance improvement.

callback-style=OLD|NEW

Callbacks are a powerful feature that allow the system administrator to customize the operation of the server. A user-supplied executable file (typically a shell script) is executed each time one of the main server actions is performed (example: granting a lease). An argument list is passed in with information about the individual client and the lease. The callback-style= tag specifies whether the old (and confusing) argument list should be used with the call-on-xxx feature described below. The new (and recommended) argument list is much simpler to use, and is identical for all of the call-on-xxx functions. The new style simply inserts a value of "00" for fields that are not sensible for a particular callback. The new argument list is:

filename: client-id htype haddr ipaddr subnet-mask lease-expiration hostname gateway

The old argument list is described for each of the individual callbacks below.

call-on-unrequited=filename

This tag specifies an executable file filename that will be called when the server receives a request to which it cannot send a response. Certain arguments will be passed in; the call executed will be:

filename: client-id htype haddr [gateway]

where client-id is the client ID in hex if present, or 00 if there is no client ID. htype is the hardware type as per the ARP section of the "Assigned Numbers" RFC. haddr is the hardware address in hex. gateway is the IP address of the bootp relay agent. If the packet was not relayed, then this field is absent.

The currently supported tags for dhcp_pool_group, dhcp_device_group, and dhcp_default_client_settings are:

allow-subnet-selection

This boolean tag specifies that this group supports the subnet selection option. However, if this tag is not specified in the dhcp_server_settings, then this option will also be ignored. This tag is inappropriate for dhcp_default_client_settings.

call-on-assignment=filename

This tag specifies the fully qualified filename to be called when an IP address has been assigned to a new client. Some arguments will be passed in, the call will be made as follows:

filename: client-id htype haddr ipaddr subnet-mask lease-expiration [hostname]

where client-id is the client ID in hex if present, or 00 if there is no client ID. htype is the hardware type as per the ARP section of the "Assigned Numbers" RFC. haddr is the hardware address in hex. ipaddr is the IP address that was assigned to the client. subnet-mask is the subnet mask of the client represented as an IP address. lease-expiration is the bootpd internal representation of when the lease will expire (based on a C call to time()), a value of ffffffff represents an infinite lease. If there is a hostname associated with this address, then it is the final argument.

call-on-decline=filename

This tag specifies the fully qualified filename to be called when an IP address has been declined by a new client. Some arguments will be passed in, the call will be made as follows:

filename: client-id htype haddr ipaddr subnet-mask

call-on-discard=filename

This tag specifies the fully qualified filename to be called when an IP address has been discarded due to a conflict. Some arguments will be passed in, the call will be made as follows:

filename: client-id htype haddr ipaddr subnet-mask

call-on-release=filename

This tag specifies the fully qualified filename to be called when an IP address has been released by a client. Some arguments will be passed in, the call will be made as follows:

filename: client-id htype haddr ipaddr lease-expiration

call-on-lease-extend=filename

This tag specifies the fully qualified filename to be called when an IP address lease for a client has been extended. Some arguments will be passed in, the call will be made as follows:

filename: client-id htype haddr ipaddr subnet-mask lease-expiration

where client-id is the client ID in hex if present, or 00 if there is no client ID. htype is the hardware type as per the ARP section of the "Assigned Numbers" RFC. haddr is the hardware address in hex. ipaddr is the IP address that was assigned to the client. subnet-mask is the subnet mask of the client represented as an IP address. lease-expiration is the bootpd internal representation of when the lease will expire (based on a C call to time()), a value of ffffffff represents an infinite lease.

call-on-discover=filename

This tag specifies the fully qualified filename to be called when the server receives a discover. It should be noted that this callback can only be used when callback-style is set to new. The format of the arguments passed to this callback is same as the format specified for callback-style=new. If a particular parameter is not known or not required, 00 can be used in it's place.

call-on-offer=filename

This tag specifies the fully qualified filename to be called when the server sends an offer to a client. It should be noted that this callback can only be used when callback-style is set to new. The format of the arguments passed to this callback is same as the format specified for callback-style=new. If a particular parameter is not known or not required, 00 can be used in it's place.

class-name=classname

This tag specifies a name to refer to a device group by. It is only applicable to dhcp_device_group. The only use that bootpd makes of this field is in logging errors found in the configuration of the group.

pool-name=poolname

This tag specifies a name to refer to a pool group by. It is only applicable to dhcp_pool_group. The only use that bootpd makes of this field is in logging errors found in the configuration of the group.

class-id=client-class

This tag specifies the client-class that clients must have to be assigned to this group. This tag is required for dhcp_device_group and is inappropriate for any other keyword. Some DHCP clients send out a client-class that identifies a class that a client belongs to. For an IP address to be assigned from a device group address pool, not only must the client be on the right subnet, it must send a request with a client-class that matches that defined for the class-id. This may be specified in either hex or in ASCII (an ASCII string must be enclosed in double quotes).

ncid

This is a boolean tag that instructs bootpd not to send the class-id back to the client. This tag is applicable only for dhcp_device_group.

re

This is a boolean tag that instructs the bootpd to match the class-id in the client's request with the class-id in any dhcp_device_group, that contains the re tag using any basic regular expression. This tag is applicable only for dhcp_device_group.

subnet-mask=mask

This tag specifies the subnet mask for the addresses in the group being defined. It is specified as an IP address. This tag is required for both dhcp_device_group and dhcp_pool_group, and is inappropriate for dhcp_default_client_settings.

addr-pool-start-address=IP-address

This tag specifies the lowest address in the pool group to be assigned. This tag is required for both dhcp_device_group and dhcp_pool_group, and is inappropriate for dhcp_default_client_settings.

addr-pool-last-address=ip-address

This tag specifies the highest address in the pool group to be assigned. This address and the addr-pool-start-address define a range of addresses that can be assigned to clients. For the server, no two group address ranges may overlap.

reserved-for-other=ip-address-list

This tag is followed by one address that falls in the range of the group. This address is reserved, and will not be assigned to any clients by the DHCP server. Alternatively, a range of addresses may be defined by giving 2 addresses, with the range being the addresses from the first address up to the second address, inclusively. This tag may be repeated to reserve more addresses in the same group. It is not appropriate for dhcp_default_client_settings.

lease-time=seconds

This tag specifies the time in seconds that a lease should be given to each client. The word "infinite" may be used to specify leases that never expire. The default is "infinite." Note that if a client asks for a shorter lease than is configured for it, it will get that shorter lease time. A lease time shorter than 120 seconds will be silently upgraded to 120.

lease-grace-period=percent

This tag specifies the time after a lease expires during which that lease will not be assigned to a new client. percent is the percentage of the configured lease time that this grace period lasts. The default is 5%.

tr=percent

This tag specifies the DHCP IP lease renewal time (T1). This is the time interval from lease assignment until when the client attempts to renew the lease. RFC1541 states that T1 defaults to half the lease duration. The minimum value is 40 percent. T1 must always be smaller than T2.

tv=percent

This tag specifies the DHCP IP lease rebind time (T2). This is the time interval from lease assignment until when the client attempts to obtain a new lease from any server. RFC1541 states that T2 defaults to 0.875 times the lease duration. The minimum value is 50 percent. T2 must always be greater than T1.

lease-policy=policy

This tag specifies whether or not the assigning of new leases can be done. If policy is set to reject-new-clients then no new clients can get a lease, and only clients with existing leases will get a response. accept-new-clients is the default.

allow-bootp-clients=boolean

This tag specifies whether or not bootp clients can be members of the group being defined. The default is false. If boolean is TRUE, then an IP address may be assigned to a client that doesn't have an entry in the bootptab file and that is on the same subnet as the group being defined. This address is treated as an infinite lease, and a boot reply is sent to the client. This tag is is not appropriate for dhcp_device_group, since bootp clients don't have a client class (and therefore a bootp client would be incapable of matching the client class of the device group). If this tag is used for dhcp_default_client_settings, then it is only applicable to pool groups.

ddns-address=ip-address

This tag specifies the IP address of the Domain Name Server (DNS) to which dynamic update requests are sent.

pcsn

This tag specifies that the name sent by client should be given preference. As a boolean tag, if set it causes bootpd to accept the name sent by the client (if any). If name is not sent by the client, bootpd tries to find one.

sp

As a boolean tag, if set it causes bootpd to not use pre-requisite section in the update request when an update request is to be sent to DNS.

DHCP/BOOTP Packet

The DHCP/BOOTP packet has the following format:

struct dhcp { 
    unsigned char   op;            /* packet opcode type */ 
    unsigned char   htype;         /* hardware addr type */ 
    unsigned char   hlen;          /* hardware addr length */ 
    unsigned char   hops;          /* gateway hops */ 
    unsigned long   xid;           /* 4 bytes transaction ID */ 
    unsigned short  secs;          /* seconds since boot began */ 
    unsigned short  flags;         /* if giaddr!=0,client flags*/ 
    struct in_addr  ciaddr;        /* client IP address */ 
    struct in_addr  yiaddr;        /* 'your' IP address */ 
    struct in_addr  siaddr;        /* server IP address */ 
    struct in_addr  giaddr;        /* gateway IP address */ 
    unsigned char   chaddr[16];    /* client hardware address */ 
    unsigned char   sname[64];     /* server host name */ 
    unsigned char   file[128];     /* boot file name */ 
    unsigned char   options[312];  /* options area */ 
}; 

DHCP Option Numbers

The DHCP/BootP options discussed above correspond to the option numbers in RFC1533 as follows:

Number	Tag	Description
1	`sm`	Subnet Mask
2	`to`	Time Offset
3	`gw`	Gateways
4	`ts`	Time Servers
5	`ns`	IEN 116 Name Servers
6	`ds`	Domain Name Servers
7	`lg`	Log Servers
8	`cs`	Cookie Servers
9	`lp`	LPR Servers
10	`im`	Impress Servers
11	`rl`	Resource Location Servers
12	`hn`	Send Host Name in reply
13	`bs`	Boot File Size
14	`md`	Merit Dump File
15	`dn`	Domain Name
16	`ss`	Swap Server
17	`rp`	Root Path
18	`ef`	Extensions Path
28	`ba`	Broadcast Address
33	`sr`	Static Routes
40	`yd`	NIS Domain
41	`ys`	NIS Servers
42	`nt`	NTP Servers
43	`V###`	Vendor Specific Information
44	`na`	NetBIOS Name Servers
45	`nb`	NetBIOS Datagram Distribution Servers
46	`nc`	NetBIOS Node Type
47	`nd`	NetBIOS Scope
48	`xf`	X Font Servers
49	`xd`	X Display Manager
51	`lease-time`	IP Address Lease Time
58	`tr`	Lease Renewal Time (T1)
59	`tv`	Lease Rebinding Time (T2)
60	`class-id`	Class Identifier
61	`ci`	Client Identifier
64	`pd`	NIS+ Domain
65	`ps`	NIS+ Servers
69	`ms`	SMTP Servers

EXAMPLES

This is an example of a /etc/bootptab file:

# Common entry 
  
global.defaults:\ 
    bf=C2300A:\ 
    hd=/usr/lib/X11/:\ 
    hn:\ 
    ht=ether:\ 
    vm=rfc1048 
  
# Now the actual individual entries 
  
xterm1:\ 
    tc=global.defaults:\ 
    ha=08000903212F:\ 
    ip=190.40.101.22 
  
xterm2:\ 
    tc=global.defaults:\ 
    ha=0800090324AC:\ 
    ip=190.40.101.35 
  
# Common relay entry. 
  
relay-default:\ 
    ht=ethernet:\ 
    bp=15.4.3.136 15.13.6.192:\ 
    th=2:\ 
    hp=5: 
  
# Relay entry for node2 
  
node2:\ 
    tc=relay-default:\ 
    ha=08000902CA00: 
  
# Group relay entry 
  
group-machines:\ 
    tc=relay-default:\ 
    ha=080009000000:\ 
    hm=080009000000: 
  
# Turn the relay off (block the relay) for the following machines. 
  
blocked-machines:\ 
    ht=ethernet:\ 
    ha=07000A000000:\ 
    hm=07000A000000: 
  
# Relay definition for all other machines. 
  
all:\ 
    tc=relay-default:\ 
    ha=000000000000:\ 
    hm=000000000000: 

This is an example of a /etc/dhcptab file:

# The first entry is for options which define the server's operation. 
  
DHCP_SERVER_SETTINGS:\ 
    call-on-unrequited="/tmp/unrequited.script" :\ 
    allow-subnet-selection :\ 
    dhcpdb-write-perf= 3 :\ 
  
# The next entry is for options that will be applied to all groups. 
# Individual options may be overridden for a specific group if the group 
# also configures the option. 
  
DHCP_DEFAULT_CLIENT_SETTINGS:\ 
    hn:\ 
    lease-time=10080:\ 
  
# The next entry defines an address pool for devices with the class 
# id "xterminal" on subnet 15.14.128.  Address lease will also be 
# granted to client requests from other subnets, with the subnet  
# selection option set to 15.14.128.255. Address leases will be  
# granted for up to 1 week. The server will use a broadcast message  
# to respond to all client 
# requests. 
  
DHCP_DEVICE_GROUP:\ 
    ba:\ 
    class-name=SUBNET_128_XTERMINAL_GROUP:\ 
    class-id="xterminal:"\ 
    allow-subnet-selection:\ 
    subnet-mask=255.255.255.0 :\ 
    addr-pool-start-address=  15.14.128.1 :\ 
    addr-pool-last-address=   15.14.128.254 :\ 
    lease-time=604800 :\ 
    lease-grace-period=5 :\ 
  
# The next entry grants IP leases to any device on subnet 
# 15.13.128.  Address will also be granted to client requests 
# from other subnets, with the subnet selection option set  
# to 15.13.128.255. The script /usr/local/bin/assignment.script  
# will be run whenever a new lease is granted. 
  
DHCP_POOL_GROUP:\ 
    pool-name=RED_SUBNET_POOL:\ 
    call-on-assignment="/usr/local/bin/assignment.script" :\ 
    allow-subnet-selection:\ 
    subnet-mask=255.255.255.0 :\ 
    addr-pool-start-address=  15.13.128.100 :\ 
    addr-pool-last-address=   15.13.128.254 :\ 
    gw=15.13.128.1 :\ 
  

This is an example of a /etc/dhcpdeny file:

# Sample /etc/dhcpdeny file 
080009000001 
0x080009000002 
# Above two clients will not be served! 

WARNINGS

Individual host entries must not exceed 1024 characters.

AUTHOR

bootpd was developed by Carnegie Mellon University, Stanford University, and HP.

FILES

/etc/bootptab
/etc/dhcptab
/etc/services