JP2000316016A - Dhcp server - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DHCP(dynamic host configuration protocol) with an excellent function of preventing double assignment. SOLUTION: The DHCP server 101 is a server that has a port connected to a network, registers a plurality of IP addresses available on the network in an assignment information table in advance and assigns the IP address registered in the assignment information table to a communication terminal on the network. In this case, the server extracts a sender IP address in a frame received at a port, registers the address to a sender IP address database and does not assign the IP address registered in the sender IP address database when assigning the IP address to a communication terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DHCP server which assigns an IP address to a communication terminal on a network, and more particularly to a DHCP server which has a function of preventing double assignment.
It is about the server.

[0002]

2. Description of the Related Art DHCP (Dynamic Host Configuration P
rotocol, RFS2131) server has a plurality of IP (Internet Protocol) addresses registered for allocation in advance,
When a request is received from a terminal which is a DHCP client, the terminal has a function of assigning an IP address to the client.

[0003] The procedure of the allocation process will be described first.
The DHCP server selects an IP address that has not been assigned to any client yet from a group of IP addresses registered inside the server. Next, in order to know whether or not the selected IP address is already used on the network, an ICMP (Internet
Control Massage Protocol) Sends an echo request. Thereafter, if a response to this request is not obtained within a predetermined time, it is determined that the terminal using the IP address does not exist on the network, and the IP address is assigned to the requesting client. If there is a response within a certain period of time, another IP address is selected without assigning the IP address, and the ICMP echo check is similarly performed. The above processing is repeatedly performed in response to a request from the client.

[0004]

SUMMARY OF THE INVENTION In the prior art, D
The HCP server performs an ICMP echo check to prevent duplicate assignment of IP addresses, but the IP address to be assigned is already used by another terminal, and that terminal temporarily goes down. In some cases, since there is no response to the ICMP echo request, the IP address is assigned to the requesting client. Thereafter, when the terminal in the down state returns, a plurality of terminals having the same IP address exist on the network, and communication between the terminals on the network cannot be performed normally.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a DHCP server having an excellent function of preventing double assignment.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a plurality of IP addresses having a port connected to a network and usable on the network are registered in advance in an assignment information table, and assigned. In a DHCP server that assigns an IP address registered in the information table to a communication terminal on a network, a source IP address of a frame received at a port is extracted and registered in a source IP address database, and the IP address is assigned to the communication terminal. Is assigned, the IP address registered in the source IP address database is not assigned.

When an IP address registered in the source IP address database is not extracted from a frame received at a port for a certain period of time, the IP address is deleted from the source IP address database and the source I address is deleted.
When an IP address registered in the P address database is extracted from a frame received at a port, the deletion of the IP address may be postponed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

As shown in FIG. 1, the DH according to the present invention
The CP server 101 is connected to a network. The terminals 111, 112, 113, 11
4, 121, 122 are connected.

[0010] The DHCP server 101 sends an I
The P address is registered in the internal assignment information table in advance, and has a function of assigning an IP address to the client when a request is received from the client.

In this function, the DHCP server 101
Has a source IP address database inside, always extracts a source IP address from a frame received at a port, and registers the IP address if it is not registered in the source IP address database. Thereafter, if a frame having the same source IP address is not received even after a certain period of time, the IP address is deleted from the source IP address database. If a frame having the same transmission source IP address is received before the fixed time has elapsed, the registration is further extended to a certain time and maintained.

When assigning an IP address, the DHCP server 101 selects an unassigned IP address from an assignment information table, further refers to a source IP address database, and determines that the IP address is
If the IP address is registered in the P address database, the selection from the assignment information table is repeated, so that an IP address not registered in the transmission source IP address database is selected. The DHCP server 101 performs an ICMP echo request check on the IP address to confirm that there is no overlap, and allocates the confirmed IP address to the client.

Here, the IP address of the DHCP server 101 is 172.17.51.1, and the IP addresses of the terminals 121 and 122 having no DHCP client function are 172.17.5.102 and 172.1, respectively.
It is 7.51.103. Also, the DHCP server 101
172.17.5 as the IP address for assignment
1.100 to 172.17.51.199 are registered, and the terminal 11 already has a DHCP client function.
1, 112, the IP addresses 172.17.51.100, 172.17.51.
It is assumed that 101 is assigned.

FIG. 2 shows the contents of the assignment information table inside the DHCP server 101 at this time. Figure 2 shows the IP
Address 172.17.51.100, 172.17.
51.101 has been assigned, and other IP addresses have not been assigned.

It is assumed that the terminals 111, 112, 121 and 122 are operating. These terminals 111, 112,
113 transmit frames to each other, the source IP address database inside the DHCP server 101 is as shown in FIG. That is, the IP address 172.17.5
1.100, 172.17.5.101, 172.1
7.5.102, 172.17.5.103 are registered. Since the registration deadline in the source IP address database is 30 seconds, the remaining registration time is 30 seconds at the time of registration, and the remaining registration time is decremented by one every elapse of one second. Is deleted.
If a frame having the same source IP address is received when the remaining registration time remains, the remaining registration time is initialized to 30 seconds.

Here, it is assumed that a machine trouble has occurred in the terminal 121 and the terminal 121 is being restarted. Alternatively, it is assumed that the terminal 121 is in a state of being unable to return an ICMP echo response due to a high load state. At this time, it is assumed that the terminal 113 is activated and transmits an address assignment request to the DHCP server 101.

In the case of the prior art, if the IP address 17
When 2.17.5.102 is selected from the assignment information table, the IP address 172.17.5.102 is selected.
Since an ICMP echo request is transmitted to the address and a response to this request cannot be obtained within a predetermined time, it is determined that the terminal 121 does not exist on the network. Thus I
IP address 172.1 by CMP echo check
Since it is determined that the assignment of 7.51.102 is possible, this IP address 172.17.5.10.
2 is assigned.

On the other hand, in the present invention, as shown in FIG. 4, the DHCP server 101 selects an unassigned IP address from the assignment information table shown in FIG. 2, and is registered in the source IP address database shown in FIG. Since an IP address that has not been selected is selected, for example, the IP address 172.17.5.104 is selected. Next, DH
The CP server 101 has an IP address of 172.17.5.
Perform ICMP echo check for 1.104. That is, if it is determined that the assignment is possible, the terminal 113
Assign the address 172.17.5.104.

Considering a case where a terminal which is a DHCP client is temporarily stopped and the IP address of the terminal is immediately assigned to another terminal, in such a case, the DHCP
It is also possible to set the CP server 101 so as not to refer to the source IP address database of FIG. 3 at the time of IP address assignment, and to use a conventional technique.

[0020]

The present invention exhibits the following excellent effects.

(1) Even if the terminal is temporarily in a down state, if communication is performed at a normal time before that, the IP address of the terminal will not be used for allocation, and double allocation will be more difficult than before. It is well prevented and communication failure on the network is prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a network to which a DHCP server according to an embodiment of the present invention is connected.

FIG. 2 is a diagram showing an assignment information table of a DHCP server according to the present invention.

FIG. 3 is a diagram showing a source IP address database of the DHCP server of the present invention.

FIG. 4 is a flowchart of a process when the DHCP server of the present invention receives an address assignment request.

[Explanation of symbols]

101 DHCP server 111, 112, 113, 114 Terminal (DHCP client) 121, 122 Terminal (non-DHCP client)

Claims (2)

[Claims] 1. A device having a port connected to a network,
Transmission of a frame received by a port in a DHCP server that registers a plurality of IP addresses usable on a network in advance in an assignment information table and assigns the IP addresses registered in the assignment information table to communication terminals on the network. The source IP address is extracted and registered in the source IP address database, and the IP
A DHCP server, wherein when assigning an address, an IP address registered in a source IP address database is not assigned. 2. When an IP address registered in a source IP address database is not extracted from a frame received at a port for a certain period of time, the IP address is deleted from the source IP address database, and is deleted from the source IP address database. 2. The DHCP server according to claim 1, wherein when a registered IP address is extracted from a frame received at the port, deletion of the IP address is postponed.