Re: [Xen-users] newbie in trouble with CentOS Xen

[Dave Stevens <geek@xxxxxxxxxxxx>]

Quoting Alexandre Kouznetsov <alk@xxxxxxxxxx>:

> El 05/04/13 20:02, Dave Stevens escribió:
> > I started apache in dom0 and from outside wa getting the default apache
> > page, have now replaced it with something slightly more meaningful.
> While testing low level connectivity (layer 2 and 3), a ping (aka  
> ICMP echo) is usually enough. A high level service, such as Apache,  
> would also work, but may introduce false positives and false  
> negatives if not used properly.
>
> > So I
> > think the xenbr1 connection to vif4.1 must not be working properly in
> > sending packets to domU's eth1
> >
> > in dom0:
> >
> > peth1     Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
> >           inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
> >           UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
> >           RX packets:118842 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:181148 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:1000
> >           RX bytes:24736385 (23.5 MiB)  TX bytes:17074473 (16.2 MiB)
> >           Interrupt:251 Base address:0xe000
> > so lots of traffic there and then:
> >
> > xenbr1    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
> >           UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
> >           RX packets:143222 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:0
> >           RX bytes:21810836 (20.8 MiB)  TX bytes:0 (0.0 b)
> >
> > so why no TX bytes?
> That is not normal. There is always feedback traffic, even if the  
> outgoing packets are routed to other interface.
> > and vif4.1 is:
> > vif4.1    Link encap:Ethernet  HWaddr FE:FF:FF:FF:FF:FF
> >           inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
> >           UP BROADCAST RUNNING NOARP  MTU:1500  Metric:1
> >           RX packets:40649 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:23529 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:500
> >           RX bytes:1138388 (1.0 MiB)  TX bytes:8233545 (7.8 MiB)
> >
> > and domU's eth1 is:
> >
> > eth1      Link encap:Ethernet  HWaddr 00:16:3E:52:61:CE
> >           inet addr:204.174.35.215  Bcast:204.174.35.255
> > Mask:255.255.255.0
> >           inet6 addr: fe80::216:3eff:fe52:61ce/64 Scope:Link
> >           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> >           RX packets:23474 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:40601 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:1000
> >           RX bytes:8214830 (7.8 MiB)  TX bytes:1705458 (1.6 MiB)
> >
> > domU is lower thandom0 because I rebooted the VM
> >
> > Does any of this suggest anything to you?
> I guess, peth1 is still within the bridge xenbr1.
>
> In a case like this, I would get a tcpdump and take a look on  
> vif4.1, xenbr1 and peth1.
> Consider using -e key, to log MAC address of the devices.
> If you ping your DomU from outside, in "normal working" case, you  
> should see a echo-request on peth1, xenbr1 and vif4.1, followed by a  
> echo-replay.
> The request should have the MAC address of your router (or host  
> within the same broadcast domain) as source, and the MAC address of  
> your DomU (as defined in it's config and shown by ifconfig) as  
> destination. The replay should have the same addresses inverted.
> If you don't see echo-request on peth1, I would troubleshoot the switch.
> If you don't see echo-request on xenbr1 or vif4.1, something is  
> wrong with how they are participating in the bridge (try add and  
> remove with brctl? see dmesg errors).
> If you don't see echo-request on eth1 in DomU, while they are  
> visible on vif4.1, it must be Xen's fault somehow.
> If you see echo-request passing through but not echo-replay, or  
> wrong MAC in it, commonly it has to do with routing errors.
> Greetings.
>
> --
> Alexandre Kouznetsov
OK, thanks for this, I'll do some more work and let you know.

Dave

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