I am presently able to ping the guest OS' (for example, I can tell because they stop pinging when the guest VMs are powered down or the network is being restarted, etc.), but none of them can ping out or perform any network tasks.
The inbound ping started responding after configuring IP forwarding and setting up the xenbr0 per http://www.jansipke.nl/using-xenserver-in-a-routed-ip-network/ and moving the VMs to the other NIC (Guest VM on XenServer unable to reach network), however, the VMs cannot ping out or reach any sort of outside connection less the gateway (the host IP), despite being able to ping in.
Is this more likely as issue on the guest OS-level, or with the network configuration of the host? I am inclined to say the former because I can ping in to the IP from outside the Xenserver's network.
Guest tools, etc. have been installed, as far as I can tell, there is no firewall issue occurring.
The guest OSes that are affected are Ubuntu 12.04 (which gets the unknown instance error, usually a /etc/udev/rules.d/... issue on VPS, but seems not to be the case here) and CentOS 6.3 neither of which have firewalls enabled:
The eth0 configuration for the CentOS VM is:
DEVICE="eth0"
BOOTPROTO="none"
DEVICE="eth0"
BOOTPROTO="none"
HWADDR="32:E8:7F:43:CF:5F"
NM_CONTROLLED="yes"
ONBOOT="yes"
TYPE="Ethernet"
UUID="a137f23c-cf18-4bb5-beb5-38ff76371363"
IPADDR="174.34.135.164"
NETMASK="255.255.255.192"
GATEWAY="174.34.135.162" [The host IP]
[root@localhost ~]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
174.34.135.128 * 255.255.255.192 U 0 0 0 eth0
link-local * 255.255.0.0 U 1002 0 0 eth0
default 174.34.135.162 0.0.0.0 UG 0 0 0 eth0
[root@localhost ~]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 32:E8:7F:43:CF:5F
inet addr:174.34.135.164 Bcast:174.34.135.191 Mask:255.255.255.192
inet6 addr: fe80::30e8:7fff:fe43:cf5f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:206999 errors:0 dropped:0 overruns:0 frame:0
TX packets:1678 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:9606174 (9.1 MiB) TX bytes:91721 (89.5 KiB)
Interrupt:246
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:10 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:616 (616.0 b) TX bytes:616 (616.0 b)
Both can hit the gateway and the resolver IPs (8.8.8.8, etc.) but cannot resolve hostnames and hit other IPs that are not in the network configuration.
The XenServer configuration may not be relevant, given that incoming ping to the Guest OS IP works and networking on the host seems to be working properly, but in any case:
[root@srv240 ~]# ifconfig |grep -A 6 "eth\|xenbr"
eth0 Link encap:Ethernet HWaddr 00:17:31:73:40:58
UP BROADCAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Interrupt:17
--
eth1 Link encap:Ethernet HWaddr 00:18:F3:63:2B:14
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1
RX packets:347427 errors:0 dropped:0 overruns:0 frame:0
TX packets:160203 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:23706160 (22.6 MiB) TX bytes:203615293 (194.1 MiB)
Interrupt:16
--
xenbr0 Link encap:Ethernet HWaddr 00:17:31:73:40:58
inet addr:174.34.135.162 Bcast:174.34.135.167 Mask:255.255.255.248
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1
RX packets:0 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:0 (0.0 b) TX bytes:0 (0.0 b)
--
xenbr1 Link encap:Ethernet HWaddr 00:18:F3:63:2B:14
inet addr:174.34.135.162 Bcast:174.34.135.167 Mask:255.255.255.248
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1
RX packets:343907 errors:0 dropped:0 overruns:0 frame:0
TX packets:43867 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:22104935 (21.0 MiB) TX bytes:196685281 (187.5 MiB)