Link drops from the modem

savualexandru · 2022-03-21T10:36:17+00:00

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savualexandru

Hello Daniele,

I hope my message finds you well.

I am having some issues with the link dropping from the modem, on the LAN side. When it is stable like most of the day it is fine, but other times like in the morning it keeps dropping and coming back up many many times.

I am runing the modem in router mode, with DHCP and WiFi disabled, so I can use my own stuff behind it. It still does NAT but that’s it.

Connected to the UPC Modem LAN, I have a 2020 Dell Precision workstation, using OPNSense as firewall, with a 4port server Intel i350-T4 NIC. This OPNSense deployment is doing DNS, DHCP, IDS, connecting the WiFi ACs, Gateway monitoring, Web proxy and some other security stuff.

One of the 4 ports on the Intel NIC, is configured as the WAN port, wich is connected directly to the UPC Modem, and sometimes the OPNSense shows link changed on this port from UP to DOWN and back to UP continuosly.

igb0: link state changed to DOWN
igb0: link state changed to UP

When this happens, the link going down and up frantically, the DNS resolution no longer works and I loose Skype for Business connectivity wich I use for work purposes.

I sometimes see dropped packets and high latency on WAN side, when monitoring ping to either one of your DNS servers or one of google’s DNS servers.

I see no errors on any of the NIC’s ports, all power settings are set to Max or Performance on Static mode, cables are sFTP Cat 6 & 7.

No link drops reported by the OPNSense on the LAN connected ports, which go to a managed HPE Switch, and no errors reported for those as well on the OPNSense server or the switch interface.

I use the UPC servers reported in the Admin > Info section of the UPC Router to forward requests to and I also use one of the to monitor the WAN sometimes (with dpinger) and it sometimes shows loss of up to 100%.

Sometimes this behavior stops after I restart the UPC Modem, sometimes it does not, today it did, and on Friday it did also.

I tried using different port from the NIC as WAN port, I tried with the on-board embedded port as well (also Intel NIC), I tried setting MAC manually in OPNSense for the WAN port, I tried setting Speed&Duplex manually on the WAN port, setting MTU & MSS manually, I changed the DNS from forwarding to resolver, nothing made a difference.

Is there anything you can check on the modem itself or related to the modem, or is there any other configuration that would involve the modem somehow that you can recommend please ?

Thank you.

Looking forward to your reply.

Kind regards,

Alexandru

Daniele_Sunrise

savualexandru All settings as well as the signal quality are ok. I recommend you to set your modem in bridge mode and then connect your router (Lan cable from the modem to your WAN port in the router) to avoid double NAT.

After that I ask you to watch it again and report back if issue still persists.

Greetings
Daniele

savualexandru

Hello Daniele,

So far so good, however I have some questions if you please: I initially set the WAN interface wich is connected into the Router in DHCP mode on my OPNSense server, but then I manually configured the DHCP set IP and Gateway, I find it more stable configured the IP in static mode on the OPNSense side.

Can I leave it like this or shoud I switch the WAN back to dhcp mode on the OPNSense side ?

Will the external IP address change on the UPC Router side ?

What IP do I use to connect to the UPC Router now, after I set it in Modem Mode ?

Thank you.

Looking forward to your reply.

Kind regards,
Alexandru

Daniele_Sunrise

savualexandru How you want to do the DHCP exactly we would like to leave to you. Basically, your router takes over the routing and firewall technology.

You can reach the modem with the IP 192.168.100.1. Furthermore the external IP changes very rarely or almost never. But you can use a DynDNS service to avoid this.

Greetings
Daniele

savualexandru

Thank you Daniele, so far all good.

No more disconnects or link drops, speed is consistent, reply is consistent, all is better it seems, now.

I used the external IP of the UPC Router as static on my WAN on OPNSense, I"ll look into DynDNS as well but at a later date.

Thank you for all your help Daniele.

Kind regards,
Alexandru