Hi Troy,
Troy Dawson wrote:
> Hi,
> I'm not in a position to test anything until next week, but I *think*
> that I have done a fresh install of SL 5.2 and not had any network
> problems with either Dom0 or DomU, but I won't be able to check until
> next week.  I might have done an upgrade on the machine I'm thinking
> of, but I really think I did a fresh install.
>
> But, just to double check.  You have turned off all firewalls and all
> selinux's, just to make sure it wasn't one of them?
> And, how are you creating your new virtual machine?
>
I have disabled SELINUX and have the same firewall rule as the working
(UPGRADED to 5.2) systems. 

I have dug a little deeper this time.  Apparently, RHEL 5.1 introduces
libvirtd, dnsmasq, and virbr0 for NAT networking for Xen DomU.  The
original bridging interface xenbr0 is there as well.  libvirtd is
interfering with xenbr0 causing tcp applications in DomU to fail for 
xenbr0 DomU,, and even for DomU in NAT (virbr0).  For example, dig
command will work for UDP but not for TCP withing DomU.

dig www.cnn.com                       works
dig +tcp www.cnn.com              times out

If I turn off libvirtd in Dom0, my Dom0 will experience tcp appliction
problem as well, for example, I can not ssh in or out of Dom0, it will
work after I restart libvirtd again. 

I am really puzzled why the upgraded system works, but not for the fresh
5.2 installation.

I have used two DomU, a fresh CentOS 5.2 and an Ubutu Hardy DomUs,  if I
copy the same set ups to the upgraded 5.2 system, they work just fine!

> Troy
>
> Zhi-Wei Lu wrote:
>> I have installed Xen Dom0 on SL 5 and CentOS 5 before and various DomU
>> under them (SL5, CentOS 5, Ubuntu).    I have upgraded these Dom0 and
>> DomU to the latest 5.2. I didn't have any network problems at all.
>>
>> Recently, I installed a new (fresh install) Dom0 in CentOS 5.2 and DomUs
>> under it, now the network won't work for these DomUs.  I can ping these
>> DomU from anywhere and I can ping from these DomU to anythere, but all
>> other network function won't work at all, such as update the DomUs.
>> From Dom0, I can ssh into DomU and vice verse, but I can not ssh into
>> DomU from anywhere else nor ssh out from DomU to anywhere else.
>> Apparently, the network bridging is not functioning properly (or
>> behaving as in the previous versions 5, 5,1).  Redhat did introduce
>> libvirtd and dnsmasq in 5.2 which were also running on my upgraded Dom0,
>> where I didn't encounter any network problem.
>>
>> I did find a post somewhere about libvirtd which the author turned off
>> libvirt to solve his/her network problem, I tried the same thing, but I
>> couldn't ssh to my Dom0 after that.
>>
>> I would appreciate if someone could help to solve this network bridging
>> problem.  Thank you.
>>
>> -- 
>> Zhi-Wei Lu
>> Bioinformatics Core
>> Genome Center
>> University of California, Davis
>> (530) 752-2698
>
>


-- 
Zhi-Wei Lu
Bioinformatics Core
Genome Center
University of California, Davis
(530) 752-2698