Configuring IPv6 for Optimal Performance and Security in Proxy Environments

This article provides a comprehensive guide to configuring IPv6 within proxy environments, addressing common issues such as DNS leaks, slow website loading, and general connectivity problems. It caters to users who want to leverage IPv6 for accessing home devices remotely or for faster IPTV streaming, while maintaining a secure and efficient network setup.

Understanding the Basics of IPv6 Configuration

Before diving into the configuration steps, it’s essential to understand the fundamentals of IPv6 and how it interacts with proxy servers. The guide assumes the reader has a basic understanding of networking concepts and has already set up a router with OpenWRT.

Disabling Conflicting Services

To start, it’s crucial to disable any conflicting services that might interfere with the IPv6 configuration. These include:

• Any currently running proxy plugins.
• Third-party DNS plugins.

This ensures a clean slate for setting up IPv6 without unexpected interactions.

Configuring Global Network Options

The first step in enabling IPv6 involves modifying the global network settings:

• Remove the ULA (Unique Local Address) prefix from the global network options.
• In the DNS advanced settings, uncheck the “Filter IPv6 resolution” option.
• Save and apply these settings.

Interface Configuration Based on Network Type

The configuration steps vary depending on the home network setup. Here are the common scenarios:

Scenario 1: Bridge Mode with PPPoE Dial-up

In this scenario, the ISP modem is in bridge mode, and the OpenWRT router handles PPPoE dial-up. A “wan6” dynamic interface should be present.

1. Edit the LAN interface and navigate to the “Advanced Settings.”
2. Set the “Assign IPv6 prefix” length to 64.
3. Choose a suffix for the LAN interface’s IPv6 address or use EUI64.
4. In the DHCPv6 settings, set RA (Router Advertisement) to “Server Mode” and disable “Local DNS server.”
5. Disable the “O” flag in RA settings and keep other settings default.
6. Save and apply all settings.

Scenario 2: Router Mode with DHCP from ISP Modem

Here, the ISP modem is in router mode, and OpenWRT acts as a secondary router, obtaining an internal IP address via DHCP.

1. Manually create a DHCPv6 interface (if one doesn’t exist). Name it “wan6,” set the protocol to DHCPv6, and select the WAN interface.
2. Configure advanced settings with defaults.
3. Set the firewall zone to WAN.
4. Save and apply the settings.

Addressing Different Outcomes in Router Mode

After configuring the WAN6 interface, one of three outcomes is possible:

• Outcome 1: The WAN6 interface obtains both an IPv6 address and a /64 prefix delegation (PD). In this case, configure the LAN interface as in Scenario 1.
• Outcome 2: The WAN6 interface obtains an IPv6 address but no PD. In this scenario, consider switching the ISP modem to bridge mode. Alternatively, use relay mode:
  • Edit the WAN6 interface, enable DHCP server, set RA to “Relay,” disable DHCPv6, and set NDP proxy to “Relay.”
  • Edit the LAN interface, setting RA and NDP to “Relay.”
  • Save and apply the settings.
• Outcome 3: The WAN interface only obtains a /128 IPv6 address, common in campus networks. In this case, NAT66 must be used:
  • In global network options, configure a ULA prefix (e.g., within the FC00::/7 range).
  • In the firewall, enable IPv6 masquerading for the WAN zone.
  • Configure the LAN interface as in Scenario 1.
  • Save and apply the settings.

Understanding IPv6 Workflow and Addressing

The router obtains an IPv6 address and prefix delegation (PD) from the ISP. When a device on the LAN requests an IPv6 address, the router responds with a Router Advertisement (RA) containing the IPv6 prefix. The device then generates its own IPv6 address using the prefix and either EUI64 or a randomly generated suffix.

EUI64 and Privacy Considerations

EUI64 uses the device’s MAC address to generate the IPv6 suffix. While straightforward, this raises privacy concerns as the MAC address is globally unique and can be used to track a device across different networks. Modern operating systems typically use randomly generated suffixes instead.

DNS Configuration in IPv6 Environments

It is a common misconception that IPv6 requires IPv6 DNS servers. IPv4 DNS servers can resolve IPv6 addresses (AAAA records) and vice versa.

Disabling IPv6 DNS to Avoid Issues

To avoid DNS leaks and proxy-related issues, it’s recommended to disable IPv6 DNS servers in the router settings. This forces all DNS queries to use IPv4, ensuring that they are properly routed through the proxy.

Testing IPv6 Connectivity

After completing the configuration, test the IPv6 connectivity by visiting an IPv6-enabled website. The browser’s developer tools can be used to verify that the connection is indeed using IPv6.

Addressing Proxy Environment Issues

When using IPv6 with proxy plugins, issues like DNS leaks and inaccessible websites can arise. These issues are often due to the proxy plugin not handling IPv6 traffic correctly. The solution is to ensure that the proxy plugin intercepts and processes all IPv6 traffic, or to disable IPv6 DNS servers.

Configuring Homeproxy and OpenClash

The guide provides specific configuration steps for Homeproxy and OpenClash, two popular proxy plugins for OpenWRT. These steps involve enabling IPv6 support in the plugin and configuring DNS settings to ensure that all traffic is properly routed.

Conclusion

By following this comprehensive guide, professionals, developers, and tech enthusiasts can successfully configure IPv6 in their OpenWRT routers while maintaining a secure and efficient proxy environment. The guide addresses common issues and provides detailed configuration steps for various network setups, ensuring that IPv6 can be leveraged for its advantages without compromising security or performance.