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Bug 1348115

Summary:	MTU setup on qr router legs sometimes does not take effect
Product:	Red Hat OpenStack	Reporter:	Ihar Hrachyshka <ihrachys>
Component:	openstack-neutron	Assignee:	Ihar Hrachyshka <ihrachys>
Status:	CLOSED DUPLICATE	QA Contact:	Toni Freger <tfreger>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	9.0 (Mitaka)	CC:	amuller, chrisw, jjoyce, nyechiel, srevivo
Target Milestone:	async	Keywords:	ZStream
Target Release:	9.0 (Mitaka)
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:
Clones:	1348116 (view as bug list)		Environment:
Last Closed:	2016-08-10 07:58:15 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1348116

Description Ihar Hrachyshka 2016-06-20 08:18:53 UTC

Description of problem: in Mitaka, there is a new MTU logic in place, where network calculated MTU is applied to all ports belonging to the network, including router legs and TAP devices.

It was revealed in upstream that the logic does not work for OVS in some cases, when there are ports that belong to networks with different MTUs. In which case MTU setup may not take effect.


Version-Release number of selected component (if applicable): this does not affect any current OSP/Liberty, but it will affect it once a rebase for a new tarball occurs. This affects all OSP/Mitaka installations.


How reproducible: always.


Steps to Reproduce:
- observe that br-int mtu = 1500
- create vlan network (mtu = 1450)
- start a nova instance using vlan network
- observe br-int mtu is now 1450
- create gre network (1458) with a subnet
- plug in the gre subnet into the router
- observe that qr device in qrouter namespace for gre network is 1450 (not 1458 as expected)


Expected results: MTU on qr device reflects network MTU.

The issue is fixed in upstream with: https://review.openstack.org/#/q/Ibd9866d2d8fe12bb253c6fb9978f583293b32734,n,z

Comment 2 Ihar Hrachyshka 2016-06-20 08:20:54 UTC

Note: this bug assumes network_device_mtu is not set on Nova or Neutron.

Comment 3 Ihar Hrachyshka 2016-08-10 07:58:15 UTC


*** This bug has been marked as a duplicate of bug 1365622 ***