Ubuntu
netplan.io package

Unable to set bridge to lower MTU that interface its attached to

Bug #1979874 reported by Mat Clarke
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
netplan
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Undecided
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netplan.io (Ubuntu)
Triaged
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Bug Description

Affected Ubuntu 20.04 and 22.04

I have two interfaces in an LACP bond that have been set to MTU 9000 as it's required for a VLAN interface that then passes through to bridge114 which needs MTU 9000. The issue I'm having is I also require bridge-lan bridge on bond0 not to go through a VLAN and this needs to be MTU to be 1500 but is set to 9000. Below is my netplan and output of "ip a"

network:
  version: 2
  renderer: networkd
  ethernets:
    enp2s0:
      optional: true
      dhcp4: false
      dhcp6: false
    enp3s0:
      optional: true
      dhcp4: false
      dhcp6: false
  bonds:
    bond0:
      interfaces: [enp2s0,enp3s0]
      dhcp4: false
      dhcp6: false
      mtu: 9000
      parameters:
        mode: 802.3ad
        lacp-rate: fast
        transmit-hash-policy: layer2
        mii-monitor-interval: 100
  vlans:
    vlan102:
      link-local: []
      accept-ra: no
      id: 102
      link: bond0
      mtu: 1500
    vlan114:
      link-local: []
      accept-ra: no
      id: 114
      link: bond0
      mtu: 9000
  bridges:
    bridge-lan:
      macaddress: 62:21:10:24:86:e7
      interfaces: [bond0]
      dhcp4: true
      dhcp6: true
      mtu: 1500
      parameters:
        stp: false
        forward-delay: 0
    bridge102:
      interfaces: [vlan102]
      mtu: 1500
      dhcp4: false
      dhcp6: false
      link-local: []
      accept-ra: no
      parameters:
        stp: false
    bridge114:
      interfaces: [vlan114]
      mtu: 9000
      dhcp4: true
      dhcp6: false
      link-local: []
      accept-ra: no
      parameters:
        stp: false

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp2s0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 9000 qdisc fq_codel master bond0 state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff permaddr 00:01:2e:67:c8:39
3: enp3s0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 9000 qdisc fq_codel master bond0 state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff permaddr 00:01:2e:67:c8:3a
4: wlp4s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether e0:94:67:76:a0:e3 brd ff:ff:ff:ff:ff:ff
5: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 9000 qdisc noqueue master bridge-lan state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff
6: bridge-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff
    inet 172.28.185.201/24 metric 100 brd 172.28.185.255 scope global dynamic bridge-lan
       valid_lft 6295sec preferred_lft 6295sec
    inet6 2a02:8010:6538:10:6021:10ff:fe24:86e7/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 86245sec preferred_lft 14245sec
    inet6 fe80::6021:10ff:fe24:86e7/64 scope link
       valid_lft forever preferred_lft forever
7: bridge102: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 72:f5:bc:58:9a:cb brd ff:ff:ff:ff:ff:ff
8: bridge114: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
    link/ether ae:56:9d:92:a6:4e brd ff:ff:ff:ff:ff:ff
    inet 172.28.187.123/24 metric 100 brd 172.28.187.255 scope global dynamic bridge114
       valid_lft 6295sec preferred_lft 6295sec
9: vlan102@bond0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge102 state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff
10: vlan114@bond0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue master bridge114 state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff
11: lxdbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 00:16:3e:4f:03:63 brd ff:ff:ff:ff:ff:ff
    inet 10.55.236.1/24 scope global lxdbr0
       valid_lft forever preferred_lft forever
    inet6 fd42:167e:91e4:b07a::1/64 scope global
       valid_lft forever preferred_lft forever
13: veth5e7b7985@if12: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge102 state UP group default qlen 1000
    link/ether 86:79:cd:04:f8:a4 brd ff:ff:ff:ff:ff:ff link-netnsid 0
15: veth5237a3b8@if14: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue master bridge114 state UP group default qlen 1000
    link/ether aa:6a:74:5b:6d:26 brd ff:ff:ff:ff:ff:ff link-netnsid 0

I can manually work around this by running "sudo ip link set mtu 1500 bridge-lan" after reboot. Still, I have to do this after every automatic reboot due to unattended upgrades or I will have networking issues with this node as bridge-lan is on an MTU 1500 VLAN.

See original description
Mat Clarke (matclarke-clarkesnet)
description: updated
Revision history for this message
Lukas Märdian (slyon) wrote (last edit ):

Could you try to use "dhcp4-overrides.use-mtu: false" and "dhcp6-overrides.use-mtu: false" on the bridge-lan interface?

I wonder if that makes any difference?

Lukas Märdian (slyon)
Changed in netplan:
status: New → Incomplete
Revision history for this message
Mat Clarke (matclarke-clarkesnet) wrote :

I don't believe this is a DHCP issues as I have 3 other ubuntu 22.04 servers that use static IP's and if the parent interface of the bridge has a 9000 MTU then the 1500 MTU is ignored on the bridge. I've made the request changes and the output is below.

'network:
  version: 2
  renderer: networkd
  ethernets:
    enp2s0:
      optional: true
      mtu: 9000
      dhcp4: false
      dhcp6: false
    enp3s0:
      optional: true
      mtu: 9000
      dhcp4: false
      dhcp6: false
  bonds:
    bond0:
      interfaces: [enp2s0,enp3s0]
      dhcp4: false
      dhcp6: false
      mtu: 9000
      parameters:
        mode: 802.3ad
        lacp-rate: fast
        transmit-hash-policy: layer2
        mii-monitor-interval: 100
  vlans:
    vlan102:
      link-local: []
      accept-ra: no
      id: 102
      link: bond0
      mtu: 1500
    vlan114:
      link-local: []
      accept-ra: no
      id: 114
      link: bond0
      mtu: 9000
  bridges:
    bridge-lan:
      macaddress: 62:21:10:24:86:e7
      interfaces: [bond0]
      dhcp4: true
      dhcp6: true
      dhcp4-overrides:
        use-mtu: false
      dhcp6-overrides:
        use-mtu: false
      mtu: 1500
      parameters:
        stp: false
        forward-delay: 0
    bridge102:
      interfaces: [vlan102]
      mtu: 1500
      dhcp4: false
      dhcp6: false
      link-local: []
      accept-ra: no
      parameters:
        stp: false
    bridge114:
      interfaces: [vlan114]
      mtu: 9000
      dhcp4: true
      dhcp6: false
      link-local: []
      accept-ra: no
      parameters:
        stp: false'

'# ip a l bridge-lan
6: bridge-lan: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 qdisc noqueue state UP group default qlen 1000
    link/ether 62:21:10:24:86:e7 brd ff:ff:ff:ff:ff:ff
    inet 172.28.185.201/24 metric 100 brd 172.28.185.255 scope global dynamic bridge-lan
       valid_lft 7037sec preferred_lft 7037sec
    inet6 2a02:8010:6538:10:6021:10ff:fe24:86e7/64 scope global dynamic mngtmpaddr noprefixroute
       valid_lft 86235sec preferred_lft 14235sec
    inet6 fe80::6021:10ff:fe24:86e7/64 scope link
       valid_lft forever preferred_lft forever'

Revision history for this message
Lukas Märdian (slyon) wrote :

Thanks for the feedback. I need to further investigate this.

Changed in netplan:
status: Incomplete → New
tags: added: rls-jj-incoming
Lukas Märdian (slyon)
Changed in netplan.io (Ubuntu):
status: New → Triaged
importance: Undecided → Medium
Lukas Märdian (slyon)
tags: added: rls-jj-notfixing
removed: rls-jj-incoming
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