Jump to content
Welcome to our new Citrix community!
  • 0

change MTU over VM


Soporte TI

Question

15 answers to this question

Recommended Posts

  • 1

Hi!

In xencenter show mtu at 9000, i use the xenserver 7.1 LTS CU2 with latest hotfixes. The xentools in windows are 7.1.1305 and linux show 7.4 or 7.10.0-1

 

if change mtu in windows with netsh the rdp access dont work

 

some idea?

 

 

  • Like 1
Link to comment
  • 0

I've not experimented with MTU within the VM, but if changing it and restarting doesn't address the MTU 

issue it would probably take some wiresharking to get it sorted. Since Linux VM's work its definitely a VM

or XenTools issue. Speaking of which, are you on the latest XenTools release ?

 

--Alan--

 

Link to comment
  • 0

I just do this generally in XenCenter, under network settings and Properties. Or from the CLI:

# xe help network-param-set
command name            : network-param-set
        reqd params     : uuid
        optional params : name-label, name-description, MTU, default-locking-mode, other-config:
        description     : Sets the parameter specified. If param-value is not given, the parameter is set to a null value. To set a (key,value) pair in a map parameter, use the syntax 'map-param:key=value'.

 

-=Tobias

Link to comment
  • 0

The only way to change the mtu on a windows vm is by running some xenstore commands on the xenserver host once the vm has booted to update the xenstoredb of the new value

 

I have got it to work once but then its reverted if the vm reboots, there is no easy way to do this and I find it very annoying. And yes on linux it works fine.

It is an issue with the xenserver drivers for windows.

 Here is the post with instructions on how to use xenstore to do this (unsupported)

 

https://discussions.citrix.com/topic/312319-xensrvr-602-jumbo-frames-in-windows-2008r2-server-not-working/?page=3#comment-1989684

 

 

Link to comment
  • 0
1 hour ago, Soporte TI said:

Hi!!

 

Tobias, but that option is only for physical networks, the question y for change mtu to VM windows only.

 

Kyle,

 

Your option is temporal, exist now something more permanent?

 

THx

Nope, I have been messing with this for years and talked to citrix multiple times.

 

As far as I know the xenstore write method is the only way to make jumbo frames work from within a windows guest vm. I doubt this is something citrix will ever fix/add into the guest drivers.

 

I'm hoping the xcp-ng team might be able to do this down the road.

Link to comment
  • 0

This is a very interesting read, I have thought all along you could do jumbo frames in a VM. 

I don't have need to push that much data to a VM, but I'm sure there are applications where

jumbo's would be helpful. I guess you could try the XCP-ng tools for Windows to see how

that works.

 

--Alan--

 

Link to comment
  • 0
On 5/3/2019 at 12:07 PM, Kyle Peterson said:

The only way to change the mtu on a windows vm is by running some xenstore commands on the xenserver host once the vm has booted to update the xenstoredb of the new value

 

I have got it to work once but then its reverted if the vm reboots, there is no easy way to do this and I find it very annoying. And yes on linux it works fine.

It is an issue with the xenserver drivers for windows.

 Here is the post with instructions on how to use xenstore to do this (unsupported)

 

https://discussions.citrix.com/topic/312319-xensrvr-602-jumbo-frames-in-windows-2008r2-server-not-working/?page=3#comment-1989684

 

 

 

Howdy, Robert here over at WANSecurity, Inc. again.

 

Thank you for the information on this topic. Like the poster, many of our customers are running XenServer, or XCP-NG. It is often much faster to use a direct iSCSI connection from the VM to the iSCSI target. For large volumes over 2TB this is the only way to do it. For our customers using our OpenNAS platform this method uses a large increase in IOPs and throughput.

 

Unfortunately the newest PV drivers, both open source and Citrix drivers still do not take into account the underlying MTU size set on the vif. We've put together this script to automatically start a VM in a paused state, update the xenstore information for each of the VMs VIFs that have an MTU greater than 1500, and then let the VM continue to boot with properly supported MTU.

 

Finally if you let the VM boot up the script will query what the PV drivers report as the windows ethernet interface device name, and prepare a couple of nice commands for you to run as administrator on your Windows system ensuring that MTU is set properly.

 

Newest version of the script should be here:

https://www.wansec.com/Downloads/XenServer/vm_start_update_xenstore_mtu.sh

 

Email us at: info @ wansec . com for assistance.

 

Also attached to this post for your convenience.

 

Enjoy!

 

vm_start_update_xenstore_mtu.txt

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...