MTU specified during neutron network create is not honored, always set to 1500

[Sridhar Venkat]

When I try to create a new neutron network with MTU say 1000, it is getting overwritten with a value of 1500.

Is MTU not settable per neutron network?

[Dariusz Smigiel (smigiel-dariusz)]

Please update your bug with additional info. Here you can find template for it: http://docs.openstack.org/developer/neutron/policies/bugs.html#bug-report-template

Thanks

[Reedip (reedip-banerjee-deactivatedaccount)]

Please share
- CLI executed to set the MTU
- Snapshot of the Results you observed

And please report the bug in the following guideline: http://docs.openstack.org/developer/neutron/policies/bugs.html#bug-report-template

This helps us understand the bug more precisely

[Praveen N (praveenn)]

In neutron.conf, advertise_mtu=True needs to be enabled in order to set desired MTU per neutron network.Please recheck.

[Ihar Hrachyshka (ihar-hrachyshka)]

No, API does not allow to set MTU. Not a bug.

[Sridhar Venkat (svenkat)]

Ihar-hrachyshka, how to set MTU, is it for entire network node? Is it not possible to set it per network at all?

[Esha Seth (eshaseth)]

how to set MTU, is it for entire network node? Is it not possible to set it per network at all?

[Ihar Hrachyshka (ihar-hrachyshka)]

You don't set MTU per network, but still each network may have a different MTU calculated by Neutron for it depending on segmentation type used. You should configure neutron.conf/ml2_conf.ini to set proper MTU options (global_physnet_mtu and friends) and allow Neutron to calculate MTU for you. API does not allow to set your own MTU.

[Esha Seth (eshaseth)]

I checked on the neutron IRC and MTU cannot be set by API/GUI/CLI. MTU is calculated by neutron as per your config options global_physnet_mtu and such, but it cant be set. There is a separate page in user guide for MTU in newton http://docs.openstack.org/draft/networking-guide/config-mtu.html

Via neutron net-update or REST API its not possible,cause I checked the parameters and it didnt have MTU. Only neutron ipsec-site-connection-update is the cli I could see MTU as a parameter.

A GET can let MTU be returned in network payload, assuming your plugin supports net-mtu API extension. POST(edit) will not work.

It was suggested, we could in theory allow to request MTUs that are lower than plugin calculated, that would be a feature request but only if there is valid usecase around to lower your MTU.

I am cancelling this defect based on this discussion