Public bug reported:
Openstack allows the user to configure a different MTU per network, with
the default taken from the ML2 neutron::plugins::ml2::path_mtu value (
minus VXLAN overhead, if used )
(overcloud) [stack@vim1 ~]$ openstack network set --mtu 1500 management
However, currently (Queens at least) the user can specify arbitrary values
(overcloud) [stack@vim1 ~]$ openstack network set --mtu 99999 management
(overcloud) [stack@vim1 ~]$ openstack network set --mtu 10 management
The maximum possible MTU is 64K, but most network equipment won't support more
than 9200-9300.
Even when using Jumbo frames and VXLAN encapsulation, practical deployments
typically wouldn't use more than 9050 byte MTUs. RFC 791 requires a minimum MTU
of 68, and IPv6 requires at least 1280
Proposal: Limit the accepted values to 1280-9250
** Affects: neutron
Importance: Undecided
Status: New
** Tags: mtu
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https://bugs.launchpad.net/bugs/1859362
Title:
Neutron accepts arbitrary MTU values for networks
Status in neutron:
New
Bug description:
Openstack allows the user to configure a different MTU per network,
with the default taken from the ML2 neutron::plugins::ml2::path_mtu
value ( minus VXLAN overhead, if used )
(overcloud) [stack@vim1 ~]$ openstack network set --mtu 1500
management
However, currently (Queens at least) the user can specify arbitrary values
(overcloud) [stack@vim1 ~]$ openstack network set --mtu 99999 management
(overcloud) [stack@vim1 ~]$ openstack network set --mtu 10 management
The maximum possible MTU is 64K, but most network equipment won't support
more than 9200-9300.
Even when using Jumbo frames and VXLAN encapsulation, practical deployments
typically wouldn't use more than 9050 byte MTUs. RFC 791 requires a minimum MTU
of 68, and IPv6 requires at least 1280
Proposal: Limit the accepted values to 1280-9250
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