We are running a linux computer with the RC7611 LTE module for network connectivity. We have noticed that DNS is taking 5 seconds resolve. After running a tcpdump, we can see that the DNS is sending an A (ip4) and AAAA (ip6) DNS request simultaneously. For some reason, the LTE modem can’t process the 2 requests at the same time, so we receive the ip4 DNS response, but not the ip6 response. This makes the DNS lookup timeout after 5 seconds, and then it retries. When linux retries the lookup, it uses “single-request” to sequentially send the ip4 and ip6 request (instead of parallel). This succeeds in 350ms. We can set the “single-request” dns option to get around this issue.
Has anyone else experienced this DNS issue?