[root@dhcp-11-59 ~]# cat /etc/kdump.conf 
nfs 10.66.8.172:/home/zhguo/tmp/nfs
path /var/crash
core_collector makedumpfile -c --message-level 1 -d 31


[root@dhcp-11-59 ~]# ifconfig | egrep -v ^\ \|^$\|^vlan\|^eth1\.\|^lo
eth0      Link encap:Ethernet  HWaddr 24:BE:05:14:95:16  
switch    Link encap:Ethernet  HWaddr 24:BE:05:14:95:16  
virbr0    Link encap:Ethernet  HWaddr 52:54:00:AC:E6:AF  
vnet0     Link encap:Ethernet  HWaddr FE:54:00:89:7D:71

Reproduce the bug on 6.7.z stream
kernel:
2.6.32-573.21.1.el6.x86_64
qemu: qemu-kvm-rhev-0.12.1.2-2.479.el6_7.4.x86_64
kexec-tools-2.0.0-286.el6_7.1.x86_64

[root@dhcp-11-59 etc]# service kdump restart
Stopping kdump:                                            [  OK  ]
Detected change(s) the following file(s):

  /etc/kdump.conf
Rebuilding /boot/initrd-2.6.32-573.20.1.el6.x86_64kdump.img
The ifcfg-vnet0 or ifcfg-xxx which contains DEVICE=vnet0 field doesn't exist.
Failed to run mkdumprd
Starting kdump:                                            [FAILED]

Verify the bug on:
kexec-tools-2.0.0-286.el6_7.2.x86_64
[root@dhcp-11-59 ~]# service kdump restart
Stopping kdump:                                            [  OK  ]
Detected change(s) the following file(s):

  /etc/kdump.conf
Rebuilding /boot/initrd-2.6.32-573.20.1.el6.x86_64kdump.img
Starting kdump:                                            [  OK  ]

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-0473.html