Xen users - Dec 2005 - AW: xen and vlans

I think it should be sufficient to do as following:
 
- create and test the vlans as normal (i think you already did this)
- try to create the bridge as follows (for the first try without
starting xend): 
 
# network-bridge start netdev=vlan100 bridge=xenbr0

at least this was working on my debian testing installation but i have a
problem now with incorrect tcp checksums in dom0 or domU.
See my post:
http://lists.xensource.com/archives/html/xen-users/2005-12/msg00412.html

Please have a look whether you have the same problem.

Thanx,
Jan


________________________________

	Von: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] Im Auftrag von Manuel da
Costa
	Gesendet: Mittwoch, 14. Dezember 2005 22:34
	An: xen users mailing list
	Betreff: [Xen-users] xen and vlans
	
	
	Hi all. 
	
	
	What is the canonical way of getting xen to fully work with
802.1q (vlans) ? After (re)searching i found many ways but so far none
is working.
	
	platform is gentoo (x86/32) and netwerk card a tg3. xen is v3. 
	
	my config is as follows ...
	
	eth0 is  simply up (with no ip) and i created several eth0.x
interfaces corresponding to several vlans. 
	eth0.10 is de ''default'' vlan (i.e. default gw). 
	
	what i want is a way of each DomU connect to the world thru it''s
vlan bridge. 
	
	for instance ... for a domU i defined   bridge=xenbr0.10. and in
/etc/xen/xend-config.sxp i defined 
	
	(network-script my-network-scripts)
	
	
	contents of /etc/xen/scripts/my-network-scripts bellow
	
	#!/bin/sh
	set -x
	dir=$(dirname "$0")
	"$dir/network-bridge" vifnum=0.25 start
	brctl addif xenbr0.25 eth0.25
	"$dir/network-bridge" vifnum=0.10 start
	brctl addif xenbr0.10 eth0.10
	--x-- 
	
	but i allways get an error saying that i need to increase the
number loopbacks because i have reached the limit. Fact is that the
limit is way higher ''cause i increased it (sucessfully) to... 100. 
	
	What am i doing wrong ? 
	
	
	Many Thanxs in advance
	
	Best Regards
	
	M. 
	



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Lockenvitz, Jan (EXT) wrote:
> I think it should be sufficient to do as following:
>  
> - create and test the vlans as normal (i think you already did this)
> - try to create the bridge as follows (for the first try without 
> starting xend):
>  
>
> # network-bridge start netdev=vlan100 bridge=xenbr0
>
> at least this was working on my debian testing installation but i have 
> a problem now with incorrect tcp checksums in dom0 or domU.
> See my post: 
> http://lists.xensource.com/archives/html/xen-users/2005-12/msg00412.html
>
> Please have a look whether you have the same problem.
>
> Thanx,
> Jan
>
This is just conjecture and I have not yet had time to verify this but I 
believe the following is happening.
802.1q vlans add 4 bytes to the packet for the vlan managment. this 
makes the max packet size 1504 bytes but the standard MTU is 1500.
The bridge software may not deal well with oversized packets.
I also found an old email that relates to this but I am not sure if it 
still holds true. http://mail-index.netbsd.org/tech-net/2002/12/10/0001.html

I believe the answer is to create the vlans on the Dom-0 and then bridge 
the device over to the Dom-U and not have the Dom-U run the vlan 
software at all.



-- 
Alvin Starr                   ||   voice: (416)585-9971
Interlink Connectivity        ||   fax:   (416)585-9974
alvin@iplink.net              ||


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