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From "Andrija Panic (JIRA)" <>
Subject [jira] [Created] (CLOUDSTACK-7790) VXLAN interface MTU change from 1450 to 1500 and JUMBRO frames
Date Sun, 26 Oct 2014 16:36:33 GMT
Andrija Panic created CLOUDSTACK-7790:

             Summary: VXLAN interface MTU change from 1450 to 1500 and JUMBRO frames
                 Key: CLOUDSTACK-7790
             Project: CloudStack
          Issue Type: Bug
      Security Level: Public (Anyone can view this level - this is the default.)
          Components: Network Controller
    Affects Versions: 4.4.1
         Environment: NOT important - CentOS 6.5, elrepo kernel 3.10 - 
            Reporter: Andrija Panic
            Priority: Critical

By default, when using vxlan as isolation method for Guest traffic - cloudstack created vxlan
vbidge and interface, and set's MTU for those to 1450 bytes.  Problem is that default OS MTU
for any VM is 1500 and all packets get droped (except maybe DHCP and ping which uses smaller

1) Current proposed solution is to change MTU inside VM/template to 1450 - which is absolutely
NOT user friendly and degrades performance

2) Better approach - set MTU on vxlan interface and bridge to a default value of 1500, and
ask ADMIN to increase MTU to 1600 bytes on physical interface ethX or cloudbrX and enable
at least 1600 frames on physical network

3) Even better - add GUI component to CloudStack for a MTU value, so the ADMIN can deploy
JUMBRO frames accross whole Guest network - this should be probably enabled per network offering,
or similar.

Current setup, requiring MTU change inside VM is not a good solution, and does not enable
user to use JUMBRO frames at all...

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