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Verizon Home Internet router (IP Passthrough) is not updating my router when its IP number changes?

I just got a Verizon LTE Home Internet router ASK-NCQ1338FA (firmware 222656), which I configured as "IP passthrough", i.e. acting as a dumb modem not a router so I can connect it to my existing router which is a TP-Link ER605 load balancing failover router.

The Verizon ASK AF is plugged into the WAN/LAN1 port (configured as dynamic IP) of the ER605

everything seems to be working fine, the router is acquiring the IP number (and DNS servers) from the Verizon router/modem.

and everything else works as advertised: the load balancing, online detection and failover (when I pull the plug on the primary WAN, it failover to the secondary Verizon within 30-40 seconds), NO-IP dynamic DNS gets updated for both WAN ports, etc.

so far so good...

until...

the Verizon router gets a new IP assigned by Verizon (which seems to happen every few days)

the ER605 System Status and the Network WAN sections still shows the previous IP number, and the connection status say "link up"

but obviously the link is useless as there is no longer a router at the previous IP number.

the ER605 "online detection" reports that it is "offline" (because it cannot route via the previous IP of the Verizon router).

oh, also the NO-IP dynamic DNS still has the previous number reported to it, which means that I cannot access my network from the outside.

the only way I found to restore connectivity is to go into the ER605 and manually disconnect and then reconnect the WAN/LAN1 connection

and only then does the ER605 acquires the new IP from the Verizon router...

not good at all 😞

I am taking advantage of the fact that NO-IP does not get updated, and set up freshwork's free freshping monitor on the WAN/LAN1 dynamic DNS domain name, which sends me an email whenever Verizon (or the primary ISP) is "offline"

so whenever I start getting these down alert notification email messages from freshping, I have to log into the ER605 and disconnect/connect the WAN/LAN1 so that the ER605 reacquires the new IP number from the Verizon router/mode.

any idea what I might be doing wrong here?

on a previous issue, Verizon would NOT provide support because of the "IP Passthrough" configuration. they have no clue what it is...

but from the little bit of research I've done (not related to a Verizon router):

"the ISP not sending the dhcp client release command from their DHCP server to the wan port to release and renew the ip address"

so it seems that the issue might be on the Verizon router when running in "IP Passthrough" mode?

if indeed so, how do I get Verizon to acknowledge and fix this issue?

if not, what might I be doing wrong? Or is it an issue with the TP-Link ER605?

Comments

Cang_Household

Is ER605 sending DHCP Discovery after the expiration of the IP address?

If you unplug/replug the WAN1, that is triggering ifup/down script on ER605. ifup/down is probably coupled to udhcpc, hence forcing it to send a DHCP Discovery.

It could be ER605 fails to send a DHCP Discovery whenever the lease expires.

The official tech support are for WAN connectivity only with VZ supported routers in a typical setup.

Atypical setups are off limits for the residential support.

AlAcrab

Thanks,

I am no expert by any means, not really sure how to find the answers to your questions.

I understand that I do not have a typical set up and I very much appreciate any help you can give me and others who reported the exact same issue, as I found by searching the net.

based on what other reported it seems that the issue might be with the Verizon device... "not sending the DHCP client release command from their DHCP server to the wan port to release and renew the IP address"

though it seems that in "IP Passthrough" the DHCP server in the Verizon device might be disabled? since obviously the IP being passed through is not one of the IP numbers in the DHCP server range 192.168.0.xxx, and if DHCP server is disabled, how can it send the "client release" command???

oh, thinking out loud, if the DHCP server is indeed disabled, the "IP Passthrough" might not be "passing through" the client release command when the Verizon IP number is changing??? just a wild guess by a clueless user...

I do see these in the ER605 log file, but I was not yet able to catch the log file during/after failure when the IP number changes...

2022-10-12 00:16:58 User.Notice Oct 12 00:16:58 ER605: 2022-10-12 00:16:58 dhcp_client<5>: WAN2: DHCP client lease expired. Began renewing the lease.
2022-10-12 00:17:02 User.Notice Oct 12 00:17:02 ER605: 2022-10-12 00:17:02 dhcp_client<5>: WAN2: DHCP client renewing IP succeeded. (IP-Address=75.xxx.xxx.x5, Mask=255.255.255.252, Gateway=75.xxx.xxx.x6)
2022-10-12 01:16:58 User.Notice Oct 12 01:16:58 ER605: 2022-10-12 01:16:58 dhcp_client<5>: WAN2: DHCP client lease expired. Began renewing the lease.
2022-10-12 01:17:02 User.Notice Oct 12 01:17:01 ER605: 2022-10-12 01:17:01 dhcp_client<5>: WAN2: DHCP client renewing IP succeeded. (IP-Address=75.xxx.xxx.x5, Mask=255.255.255.252, Gateway=75.xxx.xxx.x6)
2022-10-12 02:16:59 User.Notice Oct 12 02:16:58 ER605: 2022-10-12 02:16:58 dhcp_client<5>: WAN2: DHCP client lease expired. Began renewing the lease.
2022-10-12 02:17:02 User.Notice Oct 12 02:17:02 ER605: 2022-10-12 02:17:02 dhcp_client<5>: WAN2: DHCP client renewing IP succeeded. (IP-Address=75.xxx.xxx.x5, Mask=255.255.255.252, Gateway=75.xxx.xxx.x6)
2022-10-12 03:16:59 User.Notice Oct 12 03:16:59 ER605: 2022-10-12 03:16:59 dhcp_client<5>: WAN2: DHCP client lease expired. Began renewing the lease.
2022-10-12 03:17:03 User.Notice Oct 12 03:17:03 ER605: 2022-10-12 03:17:03 dhcp_client<5>: WAN2: DHCP client renewing IP succeeded. (IP-Address=75.xxx.xxx.x5, Mask=255.255.255.252, Gateway=75.xxx.xxx.x6)

AlAcrab

Update.

TP-Link tech support is awesome.

They verified that the issue is with the Verizon device is indeed not sending a update to the TP-Link router when the Verizon IP number changes.

so now I need to somehow get Verizon to update their firmware... not putting much hope on that 😞

meanwhile I'll get the Verizon out of IP Passthrough mode and do a double nat with the ER605.

but but but, just realized that I have dynamic DNS set up on the ER605 which communicates the IP number of the Verizon WAN port to No-IP.

there is no DDNS settings for the Verizon device...

if I use double NAT, how would I get the actual IP number of the Verizon device to report to No-IP???

Cang_Household

First of all, only Verizon can verify there's an issue with the VZ device as third parties do not have the necessary means (such as debug logs) to identify the issue.

DHCP is a Layer 7 protocol. You has chosen IP passthrough in the configure. So some basic networking knowledge here, since L7 is above IP (L3), the DHCP should be sent from your TP-Link instead of VZ router. So when in IP passthrough mode, VZ router does not take care of DHCP, so all the DHCP transactions need to be initiated and dealt with by the TP-Link.

So to summarize, VZ router should never send DHCP renews/requests when on IP passthrough mode, because the packets are passed through.

I haven't asked as to how did TP-Link determined this is a VZ router issue. Simply drawing from basic networking knowledge, their determination does not make sense.

AlAcrab

Thanks,

I indeed don't know much if anything about networking... the below is the best of my understanding:

They explained to me that their router has no way to know that the IP number of the Verizon modem has changed, and therefore cannot initiate anything.

Unless the Verizon device sends the appropriate DCHP client release command prior to the IP number change to tell the TP-Link router that the IP number was going to be changed, the TP-Link router will not get the new IP number. And apparently the Verizon modem does not send any such command...

They confirmed this by looking at their log file, and not seeing any DHCP command which was sent around the time the IP number for Verizon has changed.

Yet they could see hourly lease expiration/renewals from TP-Link dhcp_client in the log file.

2022-10-19 19:13:55 dhcp_client<5>: WAN2: DHCP client lease expired. Began renewing the lease.

2022-10-19 19:13:59 dhcp_client<5>: WAN2: DHCP client renewing IP succeeded. (IP-Address=72.105.xxx.xxx, Mask=255.255.255.128, Gateway=72.105.xxx.xxx)

If this explanation they gave me is wrong, can you please provide more technical details which I can pass on to TP-Link support?

thank you so much for your help.

Cang_Household

Sorry, but I can tell you are not understanding much, if at all, of the response I written above.

DHCP RELEASE is only sent by the DHCP client. In your setup, VZ upstream, VZ router, and TP-Link router, only TP-Link router is the DHCP client in an IP passthrough setup. To release the DHCP lease, TP-Link router needs to send DHCP RELEASE. Furthermore, NONE of the RFC mandates the use of DHCP RELEASE, so it is an option feature after all and should not introduce disruptions to connectivity.

When VZ router is in IP passthrough, it is a L2 bridge between the WAN and LAN 2, so the packets goes right through and VZ router does not retain an IP address.

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