Behaviour of the DNS client when it encounters two A records | Telit Cinterion IoT Developer Community
January 27, 2021 - 10:25am, 1254 views
How does the DNS client behave when it encounters two A records in a single DNS response? I guess the correct way would be to randomly pick one, but that might not be the case.
Does anyone know?
Hello,
Do you have any particular Thales module in mind? In general there can probably be many approaches. So that would need to be tested or consulted with R&D. I believe that DNS servers may also send this list in different orders.
Regards,
Bartłomiej
I have Cinterion ELS61-E-Rel.2 in mind. We have deployed around 100 of these, since switching from around 2000 deployed BGS2-E-REL-2. An answer for these would be welcome as well, as they still operate and do not want to break down at all. Thank you.
I will test the hypothesis that DNS servers themselves randomize entry order later tomorrow (and report back), as this would be a huge boon.
Hello,
It would be interesting to know why this is so important for your solution.
In fact all the IPs returned by the DNS server are equal. I may be wrong but I don't think that there is a standard which says that only one way of selection is right.
I checked out some pcap traces I found on my PC (probably from ELS61-E or PLS62-W) and in Wireshark it looks like the module always selected the last entry.
Regards,
Bartłomiej