DHCP Proxy Server IP Address Duplication Prevention
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Solution Overview
Problem
In networks where there is no IP reachability between a DHCP server and a client terminal, existing methods fail to confirm the use state of IP addresses, leading to potential duplicate allocations due to blocked ICMP communication.
Innovation Solution
A DHCP proxy server is introduced to confirm the use state of IP addresses by relaying ICMP or ARP requests across subnets, enabling the DHCP server to determine whether an IP address is in use, even in scenarios with communication barriers, thereby preventing duplicate allocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DHCP server uses ICMP echo requests to confirm IP address usage, then duplicate IP allocation is prevented, but the method fails when ICMP communication is blocked by firewalls or routing barriers
Solution Approach 1:
The patent introduces a proxy server as an intermediary between the DHCP server and the target network. The proxy server receives ICMP echo requests from the DHCP server, forwards them to the target network, and relays the responses back. This intermediary approach allows IP address verification to work across networks with ICMP blocking, as the proxy server operates at the application layer and can bypass network-level ICMP restrictions.
Solution Approach 2:
The patent segments the IP address verification function into separate components: the DHCP server initiates the verification request, the proxy server handles the actual ICMP communication with the target network, and the DHCP server receives the verification result. This segmentation allows each component to operate independently, with the proxy server specialized for handling ICMP communication across different network zones.
2Reliability
If multiple DHCP servers are deployed to enhance reliability, then service availability improves, but managing IP address allocation across multiple servers becomes complex
Solution Approach 1:
The patent merges the IP address verification functionality into a centralized proxy server that serves multiple DHCP servers. Instead of each DHCP server independently verifying IP addresses, they all utilize the same proxy server infrastructure. This combining approach maintains high availability through multiple DHCP servers while simplifying management by providing a unified verification service.
Solution Approach 2:
The proxy server acts as a mediator between multiple DHCP servers and the network resources they need to verify. All DHCP servers communicate their IP address verification needs through the proxy server, which centralizes the verification logic and manages the actual ICMP communications. This intermediary role simplifies the architecture by providing a single point of coordination.
3Object-affected harmful factors
If ICMP communication is blocked by firewalls for security reasons, then network security improves, but DHCP servers cannot confirm IP address usage
Solution Approach 1:
The proxy server serves as a secure intermediary that mediates between the DHCP server's need for IP verification and the network's security requirements. The proxy server is positioned to perform ICMP echo requests on behalf of the DHCP server, allowing verification to occur while maintaining the firewall's security posture. The DHCP server never directly communicates with the target network, eliminating the security risk of direct ICMP access.
Solution Approach 2:
The patent replaces the direct mechanical ICMP communication mechanism between DHCP server and target network with an application-layer substitution. Instead of using raw ICMP packets that are blocked by firewalls, the system uses a structured request-response protocol between the DHCP server and proxy server, where the proxy server handles the actual ICMP communication. This substitution allows verification to occur through a different mechanism that bypasses firewall restrictions.
Data Source
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AI summary
Provided is an information processing system capable of preventing duplicate allocation of an IP address. The information processing system includes: a DHCP server connected to a first subnet and configured to transmit, in response to a request for address allocation from a client terminal, a request message for confirming a use state of a target address, to a second subnet, and determine, upon receiving a response message including a confirmation result for the request message from the second subnet, whether or not to allocate the address to the client terminal, based on the confirmation result; and a proxy server connected to the second subnet and configured to send, upon receiving the request message from the DHCP server, an echo request for requesting a client terminal using the target address in the request message to send a reply, to a subnet to which the client terminal having requested the address allocation is connected, and transmit, to the DHCP server, the response message including presence or absence of a response to the echo request as the confirmation result.