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Bug 1344372

Summary:	Instances do not honor network MTU and global_physnet_mtu wrongly set to 1400 instead of Ethernet Standard 1500
Product:	Red Hat OpenStack	Reporter:	Sai Sindhur Malleni <smalleni>
Component:	rhosp-director	Assignee:	Angus Thomas <athomas>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Omri Hochman <ohochman>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	9.0 (Mitaka)	CC:	amuller, beagles, dbecker, ihrachys, mburns, morazi, rhel-osp-director-maint
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Hardware:	Unspecified
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Last Closed:	2017-01-17 18:14:18 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Embargoed:

Description Sai Sindhur Malleni 2016-06-09 13:46:37 UTC

Description of problem:
The global_physnet_mtu parameter in neutron.conf is set to 1400 instead of ethernet standard 1500. Also, since Mitaka allows user to set MTU per network, the MTU for the tenant networks become 1350(1400-50). At the same time /etc/neutron/dnsmasq-neutron.conf contains dhcp-option-force=26,1400 which essentially set the instance nic MTU to 1400, when all virtual networking interfaces(qbr, veth etc) are set to 1350 due to the global_physnet_mtu parameter being set to 1400. This leads to:
1. Functionality issues (no SSH due to MTU mismatch)
2. Performance degradation

Version-Release number of selected component (if applicable):
9

How reproducible:
100%

Steps to Reproduce:
1. Create tenant network on overcloud
2. Notice that neutron net-show shows the MTU as 1350
3. Launch an instance and check nic MTU-would be set to 1400

Actual results:
Instance MTU set to 1400 and tenant network MTU set to 1350

Expected results:
Instance MTU set to 1450 and Tenant network MTU set to 1450

Additional info:
Two upstream BZs here-
https://bugs.launchpad.net/tripleo/+bug/1590100
https://bugs.launchpad.net/tripleo/+bug/1590101

Comment 2 Assaf Muller 2016-12-19 13:09:14 UTC

Ihar, this bug was already fixed right?

Comment 3 Ihar Hrachyshka 2017-01-17 16:41:46 UTC

Assaf, yes, it should have been fixed already. I think we can close the bug, I just don't know which version to put here.