DHCP Table Synchronization for VLAN Switching
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Solution Overview
Problem
In conventional authentication and quarantine network systems, terminal communication is interrupted when switching between VLANs due to the need for a new IP address allocation, which occurs only after a preset lease time, causing disruptions.
Innovation Solution
Implementing a terminal affiliation switchover system that synchronizes registry information between DHCP tables for different VLANs, allowing continuous communication without changing the IP address during VLAN changes by ensuring identical mapping information across tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a new IP address is allocated to the terminal when switching VLANs, then network security and proper routing are ensured, but terminal communication is interrupted during the switch
Solution Approach 1:
The DHCP server performs preliminary actions by allocating the same IP address to the terminal in advance for both VLAN 100 and VLAN 200. The registry information in both DHCP tables is configured beforehand to include identical terminal IP address mapping information, so when VLAN switching occurs, the terminal already has the correct IP address assigned and no communication interruption occurs
Solution Approach 2:
The invention creates a copy of the terminal IP address mapping information from one DHCP table to another. The registry information in the DHCP table for VLAN 100 is copied to the DHCP table for VLAN 200, ensuring both tables have identical mapping information. This copying mechanism allows the terminal to maintain the same IP address across VLAN transitions
2Ease of operation
If different IP addresses are allocated to the terminal in different VLANs, then proper packet routing is enabled, but terminal communication continuity is broken
Solution Approach 1:
The system performs preliminary configuration by pre-allocating the same IP address to the terminal in both DHCP tables before VLAN switching occurs. This preliminary action ensures that when the terminal switches from VLAN 100 to VLAN 200, the IP address remains consistent and communication continuity is maintained while still allowing proper routing through the packet relay device
3Adaptability or versatility
If the DHCP server allocates IP addresses based on separate DHCP tables for each VLAN, then VLAN-specific network management is achieved, but IP address consistency across VLANs cannot be maintained
Solution Approach 1:
The DHCP server is designed with multi-functionality to serve multiple VLANs while maintaining IP address consistency. The registry information in DHCP tables for different VLANs is configured to contain identical terminal IP address mapping information, allowing the DHCP server to universally manage IP allocation across VLAN 100 and VLAN 200 with the same terminal IP assignments, thus achieving both VLAN-specific management and IP consistency
Data Source
AI summary
In the terminal affiliation switchover system of the invention, in the case of allocation of an IP address to one terminal in a VPN#1 in response to an IP address allocation request, a DHCP server module 121 changes registry information in a DHCP table 122 provided for the VPN#1 and simultaneously makes the change of the registry information reflected in registry of a DHCP table 222 provided for a VPN#2 via a DHCP server module 221. Similarly in the case of allocation of an IP address to one terminal in the VPN#2 in response to an IP address allocation request, the DHCP server module 221 changes the registry information in the DHCP table 222 for the VPN#2 and simultaneously makes the change of the registry information reflected in the registry of the DHCP table 122 for the VPN#1 via the DHCP server module 121.