Standby WAN interface generates traffic

Hello community,

New to Balance (here a 310X), I see traffic going out from WAN2 interface while it is in standby state.

One oddity: among ICMP probes, the Balance tries to open a SSL session with second DNS server in settings.

While I can understand the ICMP probes, I am puzzled about SYN packets on port 443 sent to, in this case,

A take on this to ask if there is a way to completely disable probes while the WAN interface is in standby. Is that possible ?


Do you have “health check” enabled (default). If so, the unit is checking to see if the connection is functional.
Alternatively, set wan to cold-standby/disabled.

Remember - cold-standby is “down/off”. Standby is “Up, but not being used”. It is this state that allows the unit to snap traffic over to a different wan quickly.

Thanks for the suggestions.

Within our context, WAN2 is p3 backup link. Unless I am wrong, “pepOS” doesn’t have a mechanism that shuts backup WAN ports not in use. Being a backup WAN, I can’t manually set it off but, fortunately, I can tweak the probes sent and I did.

Health probes put aside, I was expecting no traffic unless the port is active. Not sure about TCP/443 packets directed towards google server, is it DoH traffic ?

The less traffic is generated, the better we get: the WAN link is some satellite path with data allowance, like a SIM but much more expensive :wink:

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I share your concern and have a similar thread here:

I’d recommend you change the standby state to disconnected to limit your usage until a better solution is available.

If applicable you can also do what I am doing which is to turn it off during non-peak time. Keep in mind the current challenge is that it will be completely down regardless of the health of the other wan;s
On BR series it’s called Standby state that you want to change.
On Balance series it’s called “Connection Priority”
Change from Always-on (Priority 1) to Backup
You may also want to consider checking “Independent from Backup WANs”

Unfortunately, we need to keep it in standby because we never know when main antenna will be out of primary satellite beam (maritime). It is actually priority 3 backup.

Little update:

I still don’t know what are these SYN packets sent to first google public DNS server. It happens on all ethernet WAN ports using 3111 as source port.

The good news: TTL is 1 !

It is probably healthchecks I would bet.

With a TTL set to 1 it is useless. All these packets will end with ttl exceeded icmp reply at 2nd hop.