Incomprehensible situation with MTU OVS

plastilin

Renowned Member
Oct 9, 2012
104
5
83
Ukraine
A situation has arisen. Set to MTU 9000 via the web interface. Used by OVS. After restarting the server, the MTU on some interfaces drops to 1500 - bond and ovs-system. How can I fix this?

Code:
proxmox-ve: 7.4-1 (running kernel: 5.15.107-2-pve)
pve-manager: 7.4-3 (running version: 7.4-3/9002ab8a)
pve-kernel-5.15: 7.4-3
pve-kernel-5.15.107-2-pve: 5.15.107-2
ceph: 17.2.6-pve1
ceph-fuse: 17.2.6-pve1
corosync: 3.1.7-pve1
criu: 3.15-1+pve-1
glusterfs-client: 9.2-1
ifupdown2: 3.1.0-1+pmx4
ksm-control-daemon: 1.4-1
libjs-extjs: 7.0.0-1
libknet1: 1.24-pve2
libproxmox-acme-perl: 1.4.4
libproxmox-backup-qemu0: 1.3.1-1
libproxmox-rs-perl: 0.2.1
libpve-access-control: 7.4-3
libpve-apiclient-perl: 3.2-1
libpve-common-perl: 7.4-1
libpve-guest-common-perl: 4.2-4
libpve-http-server-perl: 4.2-3
libpve-rs-perl: 0.7.6
libpve-storage-perl: 7.4-2
libspice-server1: 0.14.3-2.1
lvm2: 2.03.11-2.1
lxc-pve: 5.0.2-2
lxcfs: 5.0.3-pve1
novnc-pve: 1.4.0-1
openvswitch-switch: 2.15.0+ds1-2+deb11u4
proxmox-backup-client: 2.4.2-1
proxmox-backup-file-restore: 2.4.2-1
proxmox-kernel-helper: 7.4-1
proxmox-mail-forward: 0.1.1-1
proxmox-mini-journalreader: 1.3-1
proxmox-widget-toolkit: 3.7.0
pve-cluster: 7.3-3
pve-container: 4.4-3
pve-docs: 7.4-2
pve-edk2-firmware: 3.20230228-2
pve-firewall: 4.3-2
pve-firmware: 3.6-5
pve-ha-manager: 3.6.1
pve-i18n: 2.12-1
pve-qemu-kvm: 7.2.0-8
pve-xtermjs: 4.16.0-1
qemu-server: 7.4-3
smartmontools: 7.2-pve3
spiceterm: 3.2-2
swtpm: 0.8.0~bpo11+3
vncterm: 1.7-1
zfsutils-linux: 2.1.11-pve1

Code:
auto lo
iface lo inet loopback

auto eno1
iface eno1 inet manual
        mtu 9000

auto eno2
iface eno2 inet manual
        mtu 9000

auto mgmt
iface mgmt inet static
        address 10.50.253.2/24
        gateway 10.50.253.254
        ovs_type OVSIntPort
        ovs_bridge vmbr0
        ovs_mtu 9000

auto cluster
iface cluster inet static
        address 10.50.252.2/24
        ovs_type OVSIntPort
        ovs_bridge vmbr0
        ovs_mtu 9000
        ovs_options tag=4043

auto cephcluster
iface cephcluster inet static
        address 10.50.251.2/24
        ovs_type OVSIntPort
        ovs_bridge vmbr0
        ovs_mtu 9000
        ovs_options tag=4045

auto cephpublic
iface cephpublic inet static
        address 10.50.250.2/24
        ovs_type OVSIntPort
        ovs_bridge vmbr0
        ovs_mtu 9000
        ovs_options tag=4053

auto bond0
iface bond0 inet manual
        ovs_bonds eno1 eno2
        ovs_type OVSBond
        ovs_bridge vmbr0
        ovs_mtu 9000
        ovs_options lacp=active bond_mode=balance-tcp

auto vmbr0
iface vmbr0 inet manual
        ovs_type OVSBridge
        ovs_ports bond0 mgmt cluster cephcluster cephpublic
        ovs_mtu 9000

Code:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc mq master ovs-system state UP mode DEFAULT group default qlen 1000
    link/ether 38:ea:a7:8e:9b:e4 brd ff:ff:ff:ff:ff:ff
    altname enp3s0f0
3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc mq master ovs-system state UP mode DEFAULT group default qlen 1000
    link/ether 38:ea:a7:8e:9b:e5 brd ff:ff:ff:ff:ff:ff
    altname enp3s0f1
4: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether fa:0a:4b:ae:8d:58 brd ff:ff:ff:ff:ff:ff
5: vmbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 38:ea:a7:8e:9b:e4 brd ff:ff:ff:ff:ff:ff
6: mgmt: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 0a:d9:01:9e:e5:1c brd ff:ff:ff:ff:ff:ff
7: cluster: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 6a:59:1a:d0:78:b7 brd ff:ff:ff:ff:ff:ff
8: cephcluster: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether d2:6c:ce:24:78:83 brd ff:ff:ff:ff:ff:ff
9: cephpublic: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 06:ef:f4:29:07:b5 brd ff:ff:ff:ff:ff:ff
10: bond0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether a2:63:0e:31:9d:28 brd ff:ff:ff:ff:ff:ff
 
ip link set bond0 mtu 9000

Command solves the problem by increasing the MTU. But as far as I know this is not a solution. :eek:
 
Last edited:

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