ER605 detecting WAN has gone offline but not reconnecting when it returns
Hi there,
I am experiencing a curious issue whereby should the WAN IP address change on my 4G/5G modem (NR5103E) which is on a passthrough to my main router (ER605), the ER605 despite being set to 10 seconds for online check interval, takes forever to detect that the connection is now offline.
Likewise, despite now being detected as offline, the dial up states it is still online.
The WAN IP address has now changed, the connection is recognised as offline however it fails to reconnect and detect the new IP and establish a connection.
Is there a setting somewhere that I've missed or is this a flaw in the ER605?
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Hi @dazmatic
Thanks for posting in our business forum.
Simple as this.
If this does not answer your question, glad to discuss this after you take a look at this article.
And hope to see some replies with Wireshark results and screenshots of your WAN info if you need to discuss.
Please mosaic your sensitive information. Here is a list of information considered sensitive:
1. Public IP address on your WAN if your WAN is.
2. Real MAC address of your device.
3. Your personal information including address, domain name, and credentials.
For troubleshooting purposes, when a WAN IP is needed, please leave some values visible for identification.
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Hi @Clive_A
Thanks for responding.
I have already seen and read through the article and previously tested as suggested.
Settings
This is primary WAN starting with 188.29.126
If I force an IP address change on the modem (by reconnecting and receiving dynamic address) the failover works as expected
There's no ping as the gateway doesn't respond to pings - but it is there.
During this time, the primary WAN is recorded as being offline
Whereas in fact, a new IP address has been issued by ISP DHCP but has not been detected or updated by ER605
Only manually forcing a disconnect/reconnect in the controller will the IP address update and connection resume.
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Is there not a script that can be run on WAN when the connection is detected as offline to force a reconnect?
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This is actually a limitation of the modem firmware and not the TPlink router.
IP passthrough does some magic with DHCP, and there are in fact two loops, Carrier<->Modem and Modem<->Router.
What you are asking for is Carrier<->Router, which is how 'bridge' mode typically works but cellular modems (as opposed to wireline modems) typically use 'IP Passthrough'. The problem comes down to how often the modem updates the LAN device with DHCP (DHCP lease times, etc etc.). When you force a reconnect, the modem should detect the change in the IP being assigned to its WAN side, and then duplicate that change via local DHCP to the LAN device. If you are able to configure the DHCP parameters on the 4G modem, try setting DHCP lease times to something like 2 min.
If anybody writes a script it will need to be you, running on a 24/7 machine behind the router. Script will need to detect WAN down, and then bounce either the modem power, or the modem link.
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I can appreciate that. DHCP is set to 1 minute but is obviously only for local LAN network.
I can't understand why Zyxel would allow IP Pass through but not refresh after IP address change when clearly the IP address has been changed and has appeared on the pass through - the ER605 merely needs to accept the renewal.
But even still, given the ER605 is designed for this situation, I would think it reasonable to expect that on loss of connection, as in the connection is detected as offline that the ER605 would release the WAN DHCP IP address and request a renew.
Otherwise the device and feature is pretty pointless.
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I hear your frustration, but you are fighting the 'link down' detection which works based on the router pinging an IP (router->Config->Advanced->Echo Server) versus the WAN interface IP which typically works on etherlink down, or IP lease expiry. In your case, your router thinks it has a happy WAN IP (but doesn't because the carrier changed it while the previous IP lease time is still good--technically this is a mismatch between the carrier and modem settings).
So either the modem, does a refresh cycle (supports RFC3203, DHCPFORCERENEW), shrinks it's lease time to 2min, or actual electrically bounces the etherport on IP change. Anyways, ball squarely in Zyxel's court. Since that's highly unlikely to happen, you're probably better off building it yourself via docker/vm/pi. Alternatively, you may be able to find a 4G device that does a better job of IP Passthrough.
Lastly, you could submit via the Requests forum a DHCP WAN lease time override (ie modem says 6h, tplink router overrides that to 2min). This wouldn't be a great deal of effort to add to code.
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