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Well, that obviously depends on how you look at it. It is of course considered a problem by some people. But it's not considered a problem by the Xen developers community, I think, because no one has so far come up with a good argument why you actually need a GUEST to have more than three virtual interfaces. It's not limiting the bandwidth (which three physical connectors could perhaps do), because the speed of each interface is limited only by CPU and memory access speed in the guest and Dom0. It is of course limiting the number of different sources that guest can get data from with only the interface as a the distinguishing factor.

Can you explain what the setup is where you need this, and why you need more than three virtual devices? It may help forward the argument for a fix, but there may also be others who have the solved the same sort of problem within the community here, without using more than three interfaces.

[Just to note: The reason it's limited to 3 interfaces is simply that's how many fit into one 4KB memory section, which makes it easy to manage in the code. Adding more interfaces would be possible, but it would complicate matters by some amount, as the interface between Dom0 and DomU is based on physical memory pages, and sending a list of those will make not only break backwards compatibility, but also complicate the common case of using (up to) three interfaces].

Finally, I'm indeed a Xen developer, but I've got very little to do with virtual network interfaces, so I may not have grasped the whole reasoning why this limit is and if/how difficult it is to change, nor any other complications or other issues involved. I also have not been involved in the decision to "not solve this problem".

But I believe that if this was actually a REAL PROBLEM to a lot of people, then it would have been solved a long time ago. It may be a case of "yes, it's possible to solve, but not enough people are asking for it", or it may simply be that it's "not a real problem".

On 5/14/07, die.5.webers@xxxxxxxxxxx <die.5.webers@xxxxxxxxxxx > wrote:

Hi Group ...

havin' read whatever I could "google" on this topic, I didn`t find any
solution:

openSuSE 10.2 (out of the box), xenkernel, running on HP Proliant DL360G5
(dual internal networking, plus additional 4-port adapter) gives me eth0 -
eth5, but only peth0 - peth3 (as well as vif0 - vif3 and consequentely
xenbr0 - xenbr3).

I increased the number of loopback-devices to 64 ... no result

Whenever I try to "/etc/xen/scripts/network-bridge start vifnum=4" I get a
message regarding to a "nonexisting veth4" ...

What am I missing

Thanks for your time

Joe

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Re: [Xen-users] Number of xenbr's limited to four on openSuSE 10.2 ?