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I've been using a combination of interface bond-, vlan- and bridge-interfaces to provide redundancy and different logical network layers to xen domU's.

This setup is working well however i'm a bit uncertain as to how different settings on these interfaces affect one-another. To illustrate, here's my setup on a typical dom0:

                 /- vlan10 -- br10
eth0 -\         /
       > bond0 <--- vlan20 -- br20
eth1 -/         \
                 \- vlan30 -- br30

Considering bond-, vlan- and bridge-interfaces are logical rather than physical, does setting MTU on these interfaces have any effect if the physical (eth0, eth1) interfaces have a different MTU set serve a purpose?

KvH
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2 Answers2

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From your example, the MTU settings on bond interface need to be as large as largest MTU settings on each VLAN. And I think you don't need to set it on slave eth0,eth1.

tonioc
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from the Red Hat site https://access.redhat.com/solutions/963753:
Issue
jumbo frames needs to be configured in the vlan tagged interface. Adding MTU=9000 in vlan tagged interface i:e ifcfg-ethX.Y or ifcfg-bondX.Y does not help and ifconfig output still shows vlan interface with MTU:1500
Resolution
When one of the VLANs belonging to the interface needs an MTU of 9000 the underlying main non-vlan interface needs to have that same MTU as well. Other VLANs may use a different MTU as per requirement. So along with adding MTU=9000 in ifcfg-ethX.Y / bondX.Y , add it in ifcfg-ethX / bondX as well.
Root Cause
Base interface of VLAN needs to have the required MTU as to propagate changes in VLAN interface.

grant
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