Can't ping host BMC from KVM guests

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mmulqu
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Joined: 2013/02/05 16:09:31

Can't ping host BMC from KVM guests

Post by mmulqu » 2019/10/11 20:46:20

I have several KVM hosts running Centos 7.7. NICs on the guests are bridged to the outside network. Everything works except for the route from the guests to the IP of their host's BMC. These are Dell servers with iDRAC using LOM instead of the dedicated NIC. For example:

kvm01 -> vm01
kvm02 -> vm02

vm01 cannot ping kvm01-bmc but can ping kvm02-bmc
vm02 cannot ping kvm02-bmc but can ping kvm01-bmc.

This is only a problem because my Zabbix server can't do any SNMPv2 checks via the iDRAC on it's KVM host. I could setup a Zabbix proxy on another machine to get around this but am hoping there's a faster/easier way to resolve this.

Here is my 'ifconfig' and 'brctl show' output.

[user@kvm01 tmp]# sudo ifconfig
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.13 netmask 255.255.255.0 broadcast 10.160.170.255
ether d0:94:66:7d:b5:fe txqueuelen 1000 (Ethernet)
RX packets 131370093 bytes 137071357574 (127.6 GiB)
RX errors 0 dropped 11039 overruns 0 frame 0
TX packets 76816178 bytes 273455588455 (254.6 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

em1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether d0:94:66:7d:b5:fe txqueuelen 1000 (Ethernet)
RX packets 1155092292 bytes 1484269211362 (1.3 TiB)
RX errors 0 dropped 180645 overruns 0 frame 0
TX packets 1733743196 bytes 1797376645783 (1.6 TiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 17

em2: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
ether d0:94:66:7d:b5:ff txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 18

lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 2882975 bytes 11770238505 (10.9 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2882975 bytes 11770238505 (10.9 GiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether fe:54:00:ef:7e:f9 txqueuelen 1000 (Ethernet)
RX packets 34457 bytes 3212348 (3.0 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 53910 bytes 90240264 (86.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

vnet1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether fe:54:00:4a:f5:3f txqueuelen 1000 (Ethernet)
RX packets 33864 bytes 3261538 (3.1 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 46210 bytes 68770083 (65.5 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

[user@kvm01 tmp]# sudo brctl show
bridge name bridge id STP enabled interfaces
br0 8000.d094667db5fe yes em1
vnet0
vnet1

Thanks!

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TrevorH
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Re: Can't ping host BMC from KVM guests

Post by TrevorH » 2019/10/12 02:03:13

And you can ping it from the host?

Last time I tried to use an idrac on a shared network connection, it disconnected the host interface while the idrac was active so rendering it utterly useless as far as I could see.
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mmulqu
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Joined: 2013/02/05 16:09:31

Re: Can't ping host BMC from KVM guests

Post by mmulqu » 2019/10/12 11:05:43

You're right. I never even thought to check that. I can't ping from the KVM hosts to their own iDRACs. It's not a KVM networking problem as I thought but something to do with the shared port. Thanks!

mmulqu
Posts: 11
Joined: 2013/02/05 16:09:31

Re: Can't ping host BMC from KVM guests

Post by mmulqu » 2019/10/12 11:15:34

Here is the answer in case anyone stumbles across this. https://www.dell.com/support/article/us ... ed?lang=en. The iDRAC has to be on a different VLAN to make this work on a shared LOM.

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TrevorH
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Re: Can't ping host BMC from KVM guests

Post by TrevorH » 2019/10/12 12:42:28

That's a useful piece of information though since we have to have an enterprise license anyway in order to use the remote console, that includes the dedicated LAN port too.
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mmulqu
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Joined: 2013/02/05 16:09:31

Re: Can't ping host BMC from KVM guests

Post by mmulqu » 2019/10/12 13:15:36

That's probably what I'll do too. Just using the dedicated NIC seems to be worth taking up the extra switch port.

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