[SOLVED] many [KNET ] pmtud: possible MTU misconfiguration detected

[TheMrg]

We get many of this errors.

Aug 02 07:41:54 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 4 link 0 but the other node is not acknowledging packets of this size.
Aug 02 07:41:54 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.
Aug 02 07:42:00 storage1 systemd[1]: Starting Proxmox VE replication runner...
Aug 02 07:42:00 storage1 systemd[1]: pvesr.service: Succeeded.
Aug 02 07:42:00 storage1 systemd[1]: Started Proxmox VE replication runner.
Aug 02 07:42:06 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 3 link 0 but the other node is not acknowledging packets of this size.
Aug 02 07:42:06 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.

MTU is 1500 we think:

ens5f1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::dac4:97ff:fed1:f19a prefixlen 64 scopeid 0x20<link>
ether d8:c4:97:d1:f1:9a txqueuelen 1000 (Ethernet)
RX packets 1071910 bytes 326660699 (311.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 7914946 bytes 11923288800 (11.1 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0


inetVPN: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255
inet6 fe80::a882:5fff:fe29:b21b prefixlen 64 scopeid 0x20<link>
ether aa:82:5f:29:b2:1b txqueuelen 1000 (Ethernet)
RX packets 865640 bytes 64577815 (61.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1580977 bytes 2246747753 (2.0 GiB)
TX errors 0 dropped 23 overruns 0 carrier 0 collisions 0

inetVPN is a tinc mesh vpn.

 

[fabian]

please provide full logs of pve-cluster and corosync ("journalctl -b pve-cluster corosync"), output of "pveversion -v" and the corosync.conf (/etc/pve/corosync.conf).

 

[TheMrg]

ifconfig inetVPN mtu 1445
seems solve the problem. we like to understand what is the reason?
tinc PING and PONG, so may the packege are to big?
ifconfig inetVPN mtu 1500 produce the error see above

 

[TheMrg]

proxmox-ve: 6.0-2 (running kernel: 5.0.15-1-pve)
pve-manager: 6.0-4 (running version: 6.0-4/2a719255)
pve-kernel-5.0: 6.0-5
pve-kernel-helper: 6.0-5
pve-kernel-4.15: 5.4-6
pve-kernel-5.0.15-1-pve: 5.0.15-1
pve-kernel-4.15.18-18-pve: 4.15.18-44
ceph: 14.2.1-pve2
ceph-fuse: 14.2.1-pve2
corosync: 3.0.2-pve2
criu: 3.11-3
glusterfs-client: 5.5-3
ksm-control-daemon: 1.3-1
libjs-extjs: 6.0.1-10
libknet1: 1.10-pve1
libpve-access-control: 6.0-2
libpve-apiclient-perl: 3.0-2
libpve-common-perl: 6.0-2
libpve-guest-common-perl: 3.0-1
libpve-http-server-perl: 3.0-2
libpve-storage-perl: 6.0-5
libqb0: 1.0.5-1
lvm2: 2.03.02-pve3
lxc-pve: 3.1.0-61
lxcfs: 3.0.3-pve60
novnc-pve: 1.0.0-60
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.0-5
pve-cluster: 6.0-4
pve-container: 3.0-3
pve-docs: 6.0-4
pve-edk2-firmware: 2.20190614-1
pve-firewall: 4.0-5
pve-firmware: 3.0-2
pve-ha-manager: 3.0-2
pve-i18n: 2.0-2
pve-qemu-kvm: 4.0.0-3
pve-xtermjs: 3.13.2-1
qemu-server: 6.0-5
smartmontools: 7.0-pve2
spiceterm: 3.1-1
vncterm: 1.6-1
zfsutils-linux: 0.8.1-pve1

logging {
debug: off
to_syslog: yes
}
nodelist {
node {
name: cluster20
nodeid: 3
quorum_votes: 1
ring0_addr: 192.168.1.20
ring1_addr: 192.168.0.20
}
node {
name: storage1
nodeid: 2
quorum_votes: 1
ring0_addr: 192.168.1.1
ring1_addr: 192.168.0.1
}
node {
name: storage2
nodeid: 4
quorum_votes: 1
ring0_addr: 192.168.1.2
ring1_addr: 192.168.0.2
}
}
quorum {
provider: corosync_votequorum
}
totem {
cluster_name: cluster
config_version: 8
interface {
bindnetaddr: 192.168.1.0
ringnumber: 0
}
interface {
bindnetaddr: 192.168.0.0
ringnumber: 1
}
ip_version: ipv4
secauth: on
rrp_mode: passive
version: 2
}

Aug 2 08:04:00 storage1 systemd[1]: Starting Proxmox VE replication runner...
Aug 2 08:04:00 storage1 systemd[1]: pvesr.service: Succeeded.
Aug 2 08:04:00 storage1 systemd[1]: Started Proxmox VE replication runner.
Aug 2 08:04:14 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 4 link 0 but the other node is not acknowledging packets of this size.
Aug 2 08:04:14 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.
Aug 2 08:04:17 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 3 link 0 but the other node is not acknowledging packets of this size.
Aug 2 08:04:17 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.
Aug 2 08:04:37 storage1 tincd[1210916]: Sending PING to storage2 (xxxxxxport 655)
Aug 2 08:04:37 storage1 tincd[1210916]: Sending PING to cluster20 (xxxxxxxport 655)
Aug 2 08:04:37 storage1 tincd[1210916]: Got PING from storage2 (xxxxxxxport 655)
Aug 2 08:04:37 storage1 tincd[1210916]: Sending PONG to storage2 (xxxxxxxport 655)
Aug 2 08:04:37 storage1 tincd[1210916]: Got PONG from storage2 (xxxxxxxport 655)
Aug 2 08:04:37 storage1 tincd[1210916]: Got PONG from cluster20 (xxxxxxxport 655)
Aug 2 08:04:40 storage1 tincd[1210916]: Got PING from cluster20 (xxxxxxxport 655)
Aug 2 08:04:40 storage1 tincd[1210916]: Sending PONG to cluster20 (xxxxxxxport 655)
Aug 2 08:04:47 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 4 link 0 but the other node is not acknowledging packets of this size.
Aug 2 08:04:47 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.
Aug 2 08:04:51 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 3 link 0 but the other node is not acknowledging packets of this size.
Aug 2 08:04:51 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.
Aug 2 08:05:00 storage1 systemd[1]: Starting Proxmox VE replication runner...
Aug 2 08:05:00 storage1 systemd[1]: pvesr.service: Succeeded.
Aug 2 08:05:00 storage1 systemd[1]: Started Proxmox VE replication runner.
Aug 2 08:05:18 storage1 pveproxy[1176018]: worker exit
Aug 2 08:05:18 storage1 pveproxy[3420]: worker 1176018 finished
Aug 2 08:05:18 storage1 pveproxy[3420]: starting 1 worker(s)
Aug 2 08:05:18 storage1 pveproxy[3420]: worker 1213601 started
Aug 2 08:05:21 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 4 link 0 but the other node is not acknowledging packets of this size.
Aug 2 08:05:21 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.
Aug 2 08:05:24 storage1 corosync[3283]: [KNET ] pmtud: possible MTU misconfiguration detected. kernel is reporting MTU: 1500 bytes for host 3 link 0 but the other node is not acknowledging packets of this size.
Aug 2 08:05:24 storage1 corosync[3283]: [KNET ] pmtud: This can be caused by this node interface MTU too big or a network device that does not support or has been misconfigured to manage MTU of this size, or packet loss. knet will continue to run but performances might be affected.

 

[fabian]

if you use knet over the tinc interface, and that actually does not support an mtu of 1500, then yes. but this means knet just showed you that your network config was wrong

 

[TheMrg]

ok, but with
ifconfig inetVPN mtu 1445
it works. any objections against the use of MTU 1445 ?

 

[fabian]

no objections.

 

[TheMrg]

Thank you so much.