USG20W-VPN Dropping Local Devices Every 10 Or So Days

DeanH

I have a customer with a USG20W-VPN running 5.10 firmware that appears to lose network connectivity (aka DHCP) to their devices on their local LAN every 10 to 13 days.  I'm leaning towards it being a switch, but I cannot rule out the ZyXEL yet.  They had a previous USG20W-VPN unit that we replaced already, thinking it might be the ZyXEL.

The DHCP lease time is set for 48 hours.  I'm thinking of increasing that to a week.

According to the customer, after rebooting, all devices get connectivity again.  I am thinking of setting a weekly reboot to see if that keeps it at bay.  If it is the POE switch dying, then the issue would still occur even after a reboot of the ZyXEL unit.

How taxing would the syslog be on the CPU on the USG20W-VPN if set to debug level and sent to an offsite server periodically?  It would need to be enabled for at least 10 or more days - unless the issue occurs sooner.  This is a small office (four users with VoIP phones and computers, plus a network printer), so not a large amount of traffic occurs regularly.

They have also changed their ISP before this as it has been occurring for a while now, and that was thought to be a possible cause.

In this instance, what have others done to troubleshoot this type of issue, or tools set up to investigate?  Any help is appreciated.

I have the diaginfo for someone at ZyXEL to look at, if it might show something.  The unit was rebooted by the customer 4.5 hours before the diaginfo was taken (and before I was informed). I took the diaginfo when I was alerted to the issue, after the fact.

Zyxel_Cooldia

Hi @DeanH,

When the issue happened, can you see DHCP DISOVERY/REQUEST packets from LAN hosts if you capture packet on USG20W-VPN ? Assume you can see DHCP packet come from lan hosts, but USG20W-VPN does not have DHCP REPLY, then we may need to to look into on USG20W-VPN.

Capture DHCP packets:

CLI:
Router> packet-trace interface lan1 extension-filter port 68



Check DHCP service status:
CLI:

Router> debug system ps | match "dhcpd"

DeanH

Hello Zyxel_Cooldia,

Thank you for your suggestion.  I will try that next time.  The problem on this one is that the customer rebooted it before calling us, so it reset whatever was occurring and cleared it before we got to look at it.

Is there a way to run those commands and dump them to a file for long term storage for a case like this?

Zyxel_Cooldia

Hi @DeanH,

You may attach USB to collect device log, but packets still need to capture when the issue happens.

DeanH

Zyxel_Cooldia, thank you for your reply.

That is what I thought.