Carrier lost and dropped errors on flannel interface
Author: marek-obuchowiczCreated Sep 4, 2026Updated Sep 4, 2026
During higher traffic times, we've noticed that prometheus metric node_network_transmit_carrier_total increases on flannel0 interface. We're using xvlan mode on k8s clusters running in AWS, managed by kops. We also observe unexpected network issues regarding node-to-node, and node-to-external-service communication during periods where this counter increases (ie. Library error: a socket error occurred, or read error on connection to (...)).
# ip -s -s link show dev flannel.1
4: flannel.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 8951 qdisc noqueue state UNKNOWN mode DEFAULT group default
link/ether a2:ae:54:71:22:58 brd ff:ff:ff:ff:ff:ff
RX: bytes packets errors dropped missed mcast
4412784279 11973699 0 0 0 0
RX errors: length crc frame fifo overrun
0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
28182728945 15251917 1 42 1 0
TX errors: aborted fifo window heartbt transns
0 0 0 0 0There are no carrier/dropped packets on underlying physical interface:
# ip -s -s link show dev ens5
2: ens5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9001 qdisc mq state UP mode DEFAULT group default qlen 1000
link/ether 0a:54:41:a1:fe:b5 brd ff:ff:ff:ff:ff:ff
RX: bytes packets errors dropped missed mcast
39702785904 38799104 0 0 0 0
RX errors: length crc frame fifo overrun
0 0 0 0 0
TX: bytes packets errors dropped carrier collsns
37987895464 35810570 0 0 0 0
TX errors: aborted fifo window heartbt transns
0 0 0 0 3
altname enp0s5Source: flannel-io/flannel