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LAN DNS forwarding
- johnpa7
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08 Mar 2023 10:34 #1
by johnpa7
LAN DNS forwarding was created by johnpa7
I have a number of IOT things.
I setup a firewall rule
Direction Lan/RT/VPN -> Wan
Source IP 192.168.0.170~192.168.0.225 Filter Block immediately
In the syslog I then get multiple entries of devices continually attempting to connect to time.google.com. To such an extent the log rapidly fills up.
I then setup LAN DNS Resolution / Conditional DNS Forwarding
time.google.com redirect to 192.168.0.37 << Synology NAS with time service enabled
The number of entries trying to connect to time.google.com falls dramatically from 1 per second to once every 2 hours
If I ping time.google.com it resolves to 192.168.0.37
If enter w32tm /stripchart /computer:time.google.com /dataonly /samples:1
returns
Tracking time.google.com [192.168.0.37:123]. << My router redirecting
Collecting 1 samples.
The current time is 08/03/2023 10:22:34.
10:22:34, +00.0226190s
Yet in In the syslog I get
[192.168.0.183](https://192.168.0.183 ) DNS -> [8.8.8.8](https://8.8.8.8 ) inquire [time.google.com](https://time.google.com )
[192.168.0.181](https://192.168.0.181 ) DNS -> [208.67.222.222](https://208.67.222.222 ) inquire [time.google.com](https://time.google.com )
Somehow the device issue an https command that is not redirect
It would appear the device not being redirect to local time server.
I am at a loss how to proceed. Any help would be grateful
Router is Vigor 2962
Draytek Switch G2280X
Ap 903
AP 1000c
Ap 802
I setup a firewall rule
Direction Lan/RT/VPN -> Wan
Source IP 192.168.0.170~192.168.0.225 Filter Block immediately
In the syslog I then get multiple entries of devices continually attempting to connect to time.google.com. To such an extent the log rapidly fills up.
I then setup LAN DNS Resolution / Conditional DNS Forwarding
time.google.com redirect to 192.168.0.37 << Synology NAS with time service enabled
The number of entries trying to connect to time.google.com falls dramatically from 1 per second to once every 2 hours
If I ping time.google.com it resolves to 192.168.0.37
If enter w32tm /stripchart /computer:time.google.com /dataonly /samples:1
returns
Tracking time.google.com [192.168.0.37:123]. << My router redirecting
Collecting 1 samples.
The current time is 08/03/2023 10:22:34.
10:22:34, +00.0226190s
Yet in In the syslog I get
[192.168.0.183](
[192.168.0.181](
Somehow the device issue an https command that is not redirect
It would appear the device not being redirect to local time server.
I am at a loss how to proceed. Any help would be grateful
Router is Vigor 2962
Draytek Switch G2280X
Ap 903
AP 1000c
Ap 802
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- bookit
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08 Mar 2023 12:23 #2
by bookit
Replied by bookit on topic Re: LAN DNS forwarding
There is a response to your post on Reddit.
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- pharcyder
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08 Mar 2023 12:47 #3
by pharcyder
Replied by pharcyder on topic Re: LAN DNS forwarding
What is the desired outcome you are looking for as its not clear?
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- johnpa7
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08 Mar 2023 13:30 #4
by johnpa7
Replied by johnpa7 on topic Re: LAN DNS forwarding
The object is to prevent a range of addresses accessing the internet.
When I block the range 192.168.0.175 ~ 192.168.0.225
The devices in this range continually try to connect to time.google.com, almost every second. Resulting in thousands of requests.
I take this as proof the firewall block works
Therefore I set up DNS forwarding for time.google.com to redirect to 192.168.0.37 synology DSM22+ with NTP service running.
Yet when I check the log there is a DNS request
[192.168.0.183](https://192.168.0.183 ) DNS -> [8.8.8.8](https://8.8.8.8 ) inquire [time.google.com](https://time.google.com )
The devices now only poll the time sever every 2 hrs. I would prefer they obtained the time from the synology.
Thanks for responding
When I block the range 192.168.0.175 ~ 192.168.0.225
The devices in this range continually try to connect to time.google.com, almost every second. Resulting in thousands of requests.
I take this as proof the firewall block works
Therefore I set up DNS forwarding for time.google.com to redirect to 192.168.0.37 synology DSM22+ with NTP service running.
Yet when I check the log there is a DNS request
[192.168.0.183](
The devices now only poll the time sever every 2 hrs. I would prefer they obtained the time from the synology.
Thanks for responding
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- pharcyder
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10 Mar 2023 17:34 #5
by pharcyder
Replied by pharcyder on topic Re: LAN DNS forwarding
If it were me, I would either add something to the local hosts file on the devices you want to re-direct so that time.google.com resolves to your Synology IP or deploy a name server like a Pihole and resolve time.google.com to your Synology there.
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- johnpa7
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14 Mar 2023 08:41 #6
by johnpa7
Replied by johnpa7 on topic Re: LAN DNS forwarding
Hi thanks for the reply, the devices which are using time.google.com are part of IoT such as light switches, smart sockets. Therefore I don't have access to the host file.
I have setup in the Lan DNS/Dns forwarding on the 2962.
which forwards local requests to time.google.com to 192.168.0.37
When I ping time.google.com returns
ping time.google.com
Pinging time.google.com [192.168.0.37] with 32 bytes of data:
Reply from 192.168.0.37: bytes=32 time=1ms TTL=64
Reply from 192.168.0.37: bytes=32 time=114ms TTL=64
192.168.0.37 is the synology running NTP service. Unfortunately there is no log function, so I can't confirm the smart switches connect to the NTP service.
From draytek log
192.168.0.190 DNS -> 8.8.8.8 inquire time.google.com
The device appears to bypass the DNS settings, an early reply from another member. mentioned a type 65 DNS request maybe the cause. Something apple implemented. I am not clear what that actually is. Perhaps a PI hole could circumvent this.
I have setup in the Lan DNS/Dns forwarding on the 2962.
which forwards local requests to time.google.com to 192.168.0.37
When I ping time.google.com returns
ping time.google.com
Pinging time.google.com [192.168.0.37] with 32 bytes of data:
Reply from 192.168.0.37: bytes=32 time=1ms TTL=64
Reply from 192.168.0.37: bytes=32 time=114ms TTL=64
192.168.0.37 is the synology running NTP service. Unfortunately there is no log function, so I can't confirm the smart switches connect to the NTP service.
From draytek log
192.168.0.190 DNS -> 8.8.8.8 inquire time.google.com
The device appears to bypass the DNS settings, an early reply from another member. mentioned a type 65 DNS request maybe the cause. Something apple implemented. I am not clear what that actually is. Perhaps a PI hole could circumvent this.
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