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amnik
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Joined: Sat Dec 31, 2022 10:35 am

CHR problem with inequality of mtu and actual mtu

Sat Dec 31, 2022 11:11 am

Hello.
I use CHR 7.6 Stable in openstack. I set 1442 MTU on private network of openstack because of a network design. The problem is CHR config MTU to 1500 and Actual MTU to 1442 by default so interface can not be enabled and work because of inequality. So for every interface I should change MTU to 1442 manually to make interface work. Is there any solution to make MTU equal to Actual MTU by default on CHR image?
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tomislav91
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Joined: Fri May 26, 2017 12:47 pm

Re: CHR problem with inequality of mtu and actual mtu

Thu Jan 12, 2023 10:56 pm

One way to do this is to edit the /etc/network/interfaces file on the CHR image and set the MTU value to 1442 for each interface that needs to have the MTU set to 1442. This file is usually where the network configuration is defined for a Debian-based system.

Alternatively, you can also set the MTU value using the command line interface by using the ifconfig command.
ifconfig <interface> mtu 1442
Another way is to use the ip command instead of ifconfig
ip link set dev <interface> mtu 1442
You can also make the changes to persist across reboots by adding the command to a startup script, such as /etc/rc.local.

You should also verify that the Openstack is configured to work with 1442 MTU.

If I mistake syntax, sorry, but I think you figure out, there is a tons of Google results about it.
 
YiHuang
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Joined: Thu May 04, 2023 6:10 pm

Re: CHR problem with inequality of mtu and actual mtu

Fri May 05, 2023 6:18 pm

Hello,
I would recommend your openstack deployment to use vlan tenant network instead of any of tunnel network like vxlan gre geneve, use vlan tenant network you have line speed, 1500 mtu, no fragmentation and here is Openstack neutron plugin driver support this use case. https://github.com/YiHuangIX/MikrotikOp ... nML2Driver
Let me know this works for you!

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