RT-AC53 - Does it have any known NTP sync Errors?

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jatin95

New Around Here
Hi,
This is my first post and after having a very bad experience from another brand I have decided to opt for ASUS RT-AC53 Router.
I faced an issue with another brand router that no matter what the NTP Time sync just always timed out.

I wish to know if ASUS RT AC53 has any known NTP sync issues? I will be using stock firmware.

Moreover if I correctly understand all NTP servers over Internet listen on UDP 123.
When the stock Firmware of RT AC53 establishes NTP request, does it do in symmetric mode or client mode?

Symmetric -- Source Port 123 and Destination Port 123 (so server sends back data to UDP 123)
Client mode -- Source port is a temporary port (ephemeral ) 1024 or above and destination is 123 (so server sends back data on that temporary port which is > 1024)

My worry is my ISP blocks inbound UDP 123 so if RT AC53 uses symmetric mode it will error out as it will be blocked at ISP firewall. ISP does not block outbound 123.
Hope my query is clear.
Thanks and regards.
 

EmeraldDeer

Very Senior Member
Hi,
This is my first post and after having a very bad experience from another brand I have decided to opt for ASUS RT-AC53 Router.
I faced an issue with another brand router that no matter what the NTP Time sync just always timed out.

I wish to know if ASUS RT AC53 has any known NTP sync issues? I will be using stock firmware.

Moreover if I correctly understand all NTP servers over Internet listen on UDP 123.
When the stock Firmware of RT AC53 establishes NTP request, does it do in symmetric mode or client mode?

Symmetric -- Source Port 123 and Destination Port 123 (so server sends back data to UDP 123)
Client mode -- Source port is a temporary port (ephemeral ) 1024 or above and destination is 123 (so server sends back data on that temporary port which is > 1024)

My worry is my ISP blocks inbound UDP 123 so if RT AC53 uses symmetric mode it will error out as it will be blocked at ISP firewall. ISP does not block outbound 123.
Hope my query is clear.
Thanks and regards.
I just ran a tcpdump on an RT-AX88U WAN eth0 and the requests are going out in client mode.

I am using Entware chronyd via ntpMerlin add-on for NTP, though.

Let us assume someone else was running stock firmware on an RT-AC53. How would they prove client mode without Entware tcpdump?
 

jatin95

New Around Here
I raised a web ticket on Asus website and after a very long time, they finally mentioned that Ac53 uses client-server mode i.e. it uses a random source port and not UDP 123 as source. So I believe NTP sync should work on my ISP who blocks 123 inbound.
 

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