ER605 v2.3.0 – LAN-to-LAN Traffic Shows WAN IP When Port Forwarding Enabled
Device/Versions:
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Router: ER605 v2, upgraded from firmware 2.2.6 → 2.3.0
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APs: EAP670, upgraded from 1.0.4 → 1.1.1
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Controller: OC 200 2.0, 5.15.24.21
Summary of Issue:
After upgrading the ER605 to v2.3.0, LAN clients connecting to a server on another LAN subnet no longer show their real source IP. Instead, the server only sees the router’s WAN IP (172.x.x.x) if a port forward is defined.
Steps to Reproduce:
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Upgrade ER605 v2 from 2.2.6 to 2.3.0.
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Create two LAN subnets (e.g. 192.168.0.0/24 for clients, 192.168.10.0/24 for servers).
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Run a simple service like
whoami
on 192.168.10.2 to report client IPs. -
From a LAN client (192.168.0.x), connect to the server by its LAN IP.
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With no port forward: server shows 192.168.0.x (expected).
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With port forward defined: server shows 172.x.x.x (WAN IP of ER605).
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What I Expected:
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LAN→LAN traffic should be routed directly, with client source IP preserved.
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Port forwarding should only affect WAN→LAN traffic.
What Actually Happens:
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LAN→LAN traffic is SNATed to the router’s WAN IP when port forwarding exists.
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This breaks correct client IP visibility and access control.
Diagram (simplified):
Wi-Fi Client (192.168.0.x) ──> ER605 ──> Server (192.168.10.2)
Reports 192.168.0.x (expected) OR Reports 172.x.x.x (wrong, when port forward exists)
Question:
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Is this NAT behavior in 2.3.0 intentional?
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If not, can TP-Link confirm whether this is a bug/regression?
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Is there a way to prevent NAT from being applied to LAN→LAN traffic?