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I created a very standard Xen-4.0 domU with network-bridge configuration. However, no packets get out from the virtual machine to the network which bridge (peth0) is attached to. From guest I can ping the hypervisor, but can't ping anything outside it.

IP addresses:

  • x.x.x.121 -- hypervisor buddha
  • x.x.x.162 -- virutal machine, xen6

What is happening? It is a very standard network configuration. With another hypervisor exactly same configuration works (same OS, same versions, same config), but with other box it doesn't.

Symptoms look similar to this, however, my network configuration seems to look fine. Any ideas?

 xen6:~$ ping -c 1 x.x.x.121 PING x.x.x.121 (x.x.x.121) 56(84) bytes of data. 64 bytes from x.x.x.121: icmp_req=1 ttl=64 time=0.093 ms --- x.x.x.121 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.093/0.093/0.093/0.000 ms 
 buddha$ sed -n '/^[^#].*\(\(network\)\|\(vif\)\)/p' xend-config.sxp (network-script network-bridge) (vif-script vif-bridge) 
 buddha# ifconfig -a eth0 Link encap:Ethernet HWaddr 00:30:48:5a:05:fa inet addr:x.x.x.121 Bcast:x.x.x.255 Mask:255.255.255.0 inet6 addr: fe80::230:48ff:fe5a:5fa/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6082 errors:0 dropped:0 overruns:0 frame:0 TX packets:1138 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:573467 (560.0 KiB) TX bytes:230756 (225.3 KiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:26 errors:0 dropped:0 overruns:0 frame:0 TX packets:26 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:2428 (2.3 KiB) TX bytes:2428 (2.3 KiB) peth0 Link encap:Ethernet HWaddr 00:30:48:5a:05:fa inet6 addr: fe80::230:48ff:fe5a:5fa/64 Scope:Link UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 RX packets:6218 errors:0 dropped:0 overruns:0 frame:0 TX packets:1141 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:693978 (677.7 KiB) TX bytes:235320 (229.8 KiB) Interrupt:26 vif1.0 Link encap:Ethernet HWaddr fe:ff:ff:ff:ff:ff inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 RX packets:3 errors:0 dropped:0 overruns:0 frame:0 TX packets:4369 errors:0 dropped:43 overruns:0 carrier:0 collisions:0 txqueuelen:32 RX bytes:84 (84.0 B) TX bytes:487332 (475.9 KiB) 
 buddha# xm network-list xen6 Idx BE MAC Addr. handle state evt-ch tx-/rx-ring-ref BE-path 0 0 00:16:3E:F3:0F:D9 0 4 15 769 /768 /local/domain/0/backend/vif/1/0 buddha# brctl show bridge name bridge id STP enabled interfaces eth0 8000.0030485a05fa no peth0 vif1.0 
 xen6# ifconfig -a eth0 Link encap:Ethernet HWaddr 00:16:3e:f3:0f:d9 inet addr:x.x.x.162 Bcast:x.x.x.255 Mask:255.255.255.0 inet6 addr: fe80::216:3eff:fef3:fd9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6870 errors:0 dropped:0 overruns:0 frame:0 TX packets:209 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:628821 (614.0 KiB) TX bytes:31636 (30.8 KiB) Interrupt:17 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:1 errors:0 dropped:0 overruns:0 frame:0 TX packets:1 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:80 (80.0 B) TX bytes:80 (80.0 B) 
 xen6:~$ ping -c 1 x.x.x.121 PING x.x.x.121 (x.x.x.121) 56(84) bytes of data. 64 bytes from x.x.x.121: icmp_req=1 ttl=64 time=0.081 ms --- x.x.x.121 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.081/0.081/0.081/0.000 ms

Here is the ethernet controller:

 02:05.0 Ethernet controller: Broadcom Corporation NetXtreme BCM5704 Gigabit Ethernet (rev 10) Subsystem: Super Micro Computer Inc Device 1648 Flags: bus master, 66MHz, medium devsel, latency 64, IRQ 26 Memory at fc9f0000 (64-bit, non-prefetchable) [size=64K] Expansion ROM at [disabled] Capabilities: [40] PCI-X non-bridge device Capabilities: [48] Power Management version 2 Capabilities: [50] Vital Product Data Capabilities: [58] MSI: Enable- Count=1/8 Maskable- 64bit+ Kernel driver in use: tg3

I read somewhere (can't recall where) that IPMI creates issues with networking. So I disabled IPMI.

 motiejus@buddha> uname -a Linux buddha 2.6.32-5-xen-amd64 #1 SMP Mon Jan 16 20:48:30 UTC 2012 x86_64 GNU/Linux motiejus@buddha> lsb_release -a Distributor ID: Debian Description: Debian GNU/Linux 6.0.4 (squeeze) Release: 6.0.4 Codename: squeeze

Update from pastebin-data (routing info and ping-results):

Xen6: Destination Gateway Genmask Flags MSS Window irtt Iface x.x.x.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 x.x.x.1 0.0.0.0 UG 0 0 0 eth0 Buddha: Destination Gateway Genmask Flags MSS Window irtt Iface x.x.x.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 0.0.0.0 x.x.x.1 0.0.0.0 UG 0 0 0 eth0 xen6:~$ ping -c1 x.x.x.1 PING x.x.x.1 (x.x.x.1) 56(84) bytes of data. --- x.x.x.1 ping statistics --- 1 packets transmitted, 0 received, 100% packet loss, time 0ms buddha# tcpdump -nni eth0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes 22:51:01.977068 IP x.x.x.162 > x.x.x.1: ICMP echo request, id 2632, seq 1, length 64 However, x.x.x.1 does not receive the ICMP request. buddha# ping -c1 x.x.x.1 PING x.x.x.1 (x.x.x.1) 56(84) bytes of data. 64 bytes from x.x.x.1: icmp_req=1 ttl=255 time=0.403 ms --- x.x.x.1 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 0.403/0.403/0.403/0.000 ms
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  • I put the info of your comments into your question. So basically the ping from the DomU seems to go out (through the bridge to the physical interface), but no reply comes in. Is your DomUs MAC-adress used elsewhere in the network? Commented Mar 17, 2012 at 21:26
  • @Nills thanks for editing the post! According to tcpdump on buddha, it comes out through the interface, but on the target host it doesn't come in. Seems like packet is stuck in the NIC itself somehow. No other host is using the same MAC (according to arping). I would suspect ethernet drivers.. Will search for them. Commented Mar 17, 2012 at 22:01
  • Looks exactly like this. I once managed to boot Xen, and hypervisor had no access to the internet, but guest did. However, the workaround is for BCM5708, and my card is BCM5707. My card uses tg3, and the one mentioned in thread is bnx2. There is no such thing as "management firmware" in BCM5707. Disabling IPMI does not help. Commented Mar 18, 2012 at 15:10
  • @Nils please post this as an answer so I can upvote it. That's correct! Commented Mar 19, 2012 at 16:41
  • Great. Did they tell it anyone?-( Commented Mar 19, 2012 at 21:52

2 Answers 2

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Is "MAC based" security activated by your network department? This sounds to me as if only the first outgoing MAC on the physical line is being accepted.

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As I remember my problem was the same. Turning on the arp cache solved my problem, might work for you as well.

Insert these lines to /etc/sysctl.conf:

net.ipv4.ip_forward = 1 net.ipv4.conf.eth0.proxy_arp = 1

I use a routed network so there is no peth0, maybe you need to enable it:

net.ipv4.conf.peth0.proxy_arp = 1
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    but first try command: "arp" in Dom0 and DomU and if you don't see the remote end ip and MAC pair, this is the problem. Commented May 28, 2013 at 23:34

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