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mysql replication to rds via ipsec vpn error writing communication packets but it worked for month until now | the had multiple connections erros but now its stable and other DB are replicating fine but still got errors on this one
mysql log show multiple errors like : 

200328  0:10:10 [Note] Start binlog_dump to slave_server(1376194300), pos(mysql-bin.001418, 356837512)
200328  0:11:02 [Note] Start binlog_dump to slave_server(1376194300), pos(mysql-bin.001418, 356845757)
**200328  0:11:04 [Warning] Aborted connection 223664992 to db: 'unconnected' user: 'percona' host: '10.106.79.80' (Got an error writing communication packets)**
200328  0:11:06 [Note] Start binlog_dump to slave_server(1376194300), pos(mysql-bin.001418, 356845757)
200328  0:11:10 [Note] Start binlog_dump to slave_server(1376194300), pos(mysql-bin.001418, 356876615)
200328  0:12:01 [Note] Start binlog_dump to slave_server(1376194300), pos(mysql-bin.001418, 356942218)

and a packet capture shows many tcp retransmission flag when the replication hangs : 

192.168.12.53  10.106.79.80    TCP 1427    [TCP Retransmission] 3306 → 51970 [ACK] Seq=718 Ack=439 Win=29056 Len=1363 TSval=1668416099 TSecr=294240053364
192.168.12.53   10.106.79.80    TCP 1427    [TCP Retransmission] 3306 → 51970 [ACK] Seq=718 Ack=439 Win=29056 Len=1363 TSval=1668416099 TSecr=2942400533
192.168.12.53   10.106.79.80    TCP 1427    [TCP Retransmission] 3306 → 51970 [ACK] Seq=718 Ack=439 Win=29056 Len=1363 TSval=1668416372 TSecr=2942400533
Oussema Beya
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  • Did you ever figure this out? We are getting the same issue. – mikemike396 May 01 '20 at 14:05
  • yep i got it all figured out !! it was the MTU value , on pfsense i activated MSS clamping on IPSec advanced settings and set Maximum MSS to 1410. working like a charm – Oussema Beya May 21 '20 at 09:31

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