kvm Bridge issue - no network to guest

Question

I currently have a Proxmox (debian) KVM host running multiple OpenVZ Containers for general usage, I am looking at creating a KVM VM however I'm unable to get networking to work for the CentOS KVM Guest.

please find network configuration from Host:

# ifconfig
eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx
          inet6 addr: fe80::22cf:30ff:fe19:7b67/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:41861518 errors:0 dropped:0 overruns:0 frame:0
          TX packets:23326041 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:16692957938 (xx.x GiB)  TX bytes:16624094064 (xx.x GiB)
          Interrupt:47 Memory:fbfe0000-fc000000

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:1805386 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1805386 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:532155476 (507.5 MiB)  TX bytes:532155476 (507.5 MiB)

vmbr0     Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx
          inet addr:88.xxx.xxx.229  Bcast:88.xxx.xxx.xxx  Mask:255.255.252.0
          inet6 addr: fe80::22cf:30ff:fe19:7b67/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:38116128 errors:0 dropped:0 overruns:0 frame:0
          TX packets:21500108 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:15771625496 (xx.x GiB)  TX bytes:16504698806 (xx.x GiB)

and Route from host:

# route -n
Kernel IP routing table
Destination     Gateway         Genmask           Flags Metric Ref    Use Iface
88.xxx.xxx.109  0.0.0.0         255.xxx.xxx.xxx   UH    0      0        0 venet0
88.xxx.xxx.0    0.0.0.0         255.xxx.xxx.xxx   U     0      0        0 vmbr0
0.0.0.0         88.xxx.xxx.1    0.0.0.0           UG    0      0        0 vmbr0

From the guest CentOS KVM VM:

#ifconfig
    eth0      Link encap:Ethernet  HWaddr xx:xx:xx:xx:xx:xx
              inet addr:88.xxx.xxx.252  Bcast:88.xxx.xxx.255  Mask:255.255.252.0
              inet6 addr: fe80::22cf:30ff:fe19:7b67/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:38116128 errors:0 dropped:0 overruns:0 frame:0
              TX packets:21500108 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:0
              RX bytes:15771625496 (xx.x GiB)  TX bytes:16504698806 (xx.x GiB)

    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:1805386 errors:0 dropped:0 overruns:0 frame:0
              TX packets:1805386 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:0
              RX bytes:532155476 (507.5 MiB)  TX bytes:532155476 (507.5 MiB)

Routes from Guest:

#route -n
Kernel IP routing table
Destination     Gateway       Genmask        Flags Matric  Ref   Use  Iface
88.xxx.xxx.0    0.0.0.0       255.255.252.0  U     0       0     0    eth0
169.254.0.0     0.0.0.0       255.255.0.0    U     0       0     0    eth0
0.0.0.0         88.xxx.xxx.1  0.0.0.0        UG    0       0     0    eth0

a ping from the host to the guest is coming back with:

# ping 88.xxx.xxx.252
PING 88.xxx.xxx.xxx (88.xxx.xxx.252) 56(84) bytes of data.
From 88.xxx.xxx.229 icmp_seq=1 Destination Host Unreachable
From 88.xxx.xxx.229 icmp_seq=2 Destination Host Unreachable
From 88.xxx.xxx.229 icmp_seq=3 Destination Host Unreachable
--- 88.208.236.252 ping statistics ---
4 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3016ms

Any help would be grealy appreciated!

EDIT Sorry forgot to include brctl output

# brctl show
bridge name     bridge id               STP enabled     interfaces
vmbr0           8000.20cf30197b67       no              eth0

Solution

I'm not that knowledgeable on KVM, but based on what I know to be true for Xen it would seem that you're missing an interface on your bridge - you only have your physical host interface there, but it should also list whatever network device your guest is using on the host. I see a venet0 interface mentioned on the host's routing table, can you please replace the ifconfig with a ifconfig -a?

If venet0 turns out to be the guest's interface, you should probably add it to the bridge using brctl addif vmbr0 venet0. Keep in mind though that the routing table shows that the host thinks the IP "on the other side" of the link to be .109, so you may have a configuration issue right there if it turns out that's the right interface. Though deleting the route through venet0 should be enough if it belongs to the bridge.

Comments

[davidcollom]

Hi, Thanks for the Input, Marked question as correct after reading your comment I noticed that you where correct that there was an interface missing from the bridge. After shutting down the guest and starting (not a reboot) the additional interface appeared within the bridge and networking was successfull when Guest Booted!! Thank you very much!