DHCP server not responding to requests from KVM guest

Question

I've setup a DHCP server on my Debian server (Proxmox) so that I can provision IPs to my KVM guests on the server automatically. For some reason the DHCP server (isc-dhcp-server) isn't responding to requests for an IP. The DHCP server is set to listen to a bridge interface I've created called vmbr1 and I know requests are getting through to the host from the KVM guest as I've tested it through dhcpdump -i vmbr1.

I've obviously made a mistake somewhere, can anyone spot it? I've included my configuration files below.

dhcp.conf file:

ddns-update-style none;
deny declines;
deny bootp;
default-lease-time 600;
max-lease-time 7200;
log-facility local7;
subnet 192.168.0.0 netmask 255.255.255.224 {
     interface vmbr1;
     option routers 192.168.0.5;
     option broadcast-address 192.168.0.31;
     option ntp-servers 192.168.0.101;
     option domain-name-servers 192.168.0.101;
     option netbios-name-servers 192.168.0.101;
     option netbios-node-type 2;
     default-lease-time 86400;
     max-lease-time 86400;
     #vmbr1ipv4
      host 104 {hardware ethernet 1A:27:59:82:39:8E;fixed-address 95.141.36.124;}
}

isc-dhcp-server file:

# Defaults for isc-dhcp-server initscript
# sourced by /etc/init.d/isc-dhcp-server
# installed at /etc/default/isc-dhcp-server by the maintainer scripts

#
# This is a POSIX shell fragment
#

# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
#DHCPD_CONF=/etc/dhcp/dhcpd.conf

# Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
#DHCPD_PID=/var/run/dhcpd.pid

# Additional options to start dhcpd with.
#       Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
#OPTIONS=""

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#       Separate multiple interfaces with spaces, e.g. "eth0 eth1".
INTERFACES="vmbr1"

interfaces file on host:

# network interface settings
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual

auto vmbr0
iface vmbr0 inet static
        address  95.141.36.188
        netmask  255.255.255.0
        gateway  95.141.36.1
        broadcast  95.141.36.255
        bridge_ports eth0
        bridge_stp off
        bridge_fd 0
        network 95.141.36.0
        bridge_maxwait 0

auto vmbr1
iface vmbr1 inet static
        address  192.168.0.5
        netmask  255.255.255.224
        bridge_ports none
        bridge_stp off
        bridge_fd 0

Example request from KVM guest to host server through vmbr1 using dhcpdump -i vmbr1:

  TIME: 2014-05-28 21:40:14.232
    IP: 0.0.0.0 (1a:27:59:82:39:8e) > 255.255.255.255 (ff:ff:ff:ff:ff:ff)
    OP: 1 (BOOTPREQUEST)
 HTYPE: 1 (Ethernet)
  HLEN: 6
  HOPS: 0
   XID: 599fa654
  SECS: 0
 FLAGS: 0
CIADDR: 0.0.0.0
YIADDR: 0.0.0.0
SIADDR: 0.0.0.0
GIADDR: 0.0.0.0
CHADDR: 1a:27:59:82:39:8e:00:00:00:00:00:00:00:00:00:00
 SNAME: .
 FNAME: .
OPTION:  53 (  1) DHCP message type         1 (DHCPDISCOVER)
OPTION:  55 (  8) Parameter Request List      1 (Subnet mask)
                         28 (Broadcast address)
                          2 (Time offset)
                          3 (Routers)
                         15 (Domainname)
                          6 (DNS server)
                         12 (Host name)
                         42 (NTP servers)

OPTION:  60 (  3) Vendor class identifier   d-i
---------------------------------------------------------------------------

Output from dhcpd

Internet Systems Consortium DHCP Server 4.2.2
Copyright 2004-2011 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
WARNING: Host declarations are global.  They are not limited to the scope you declared them in.
Wrote 0 deleted host decls to leases file.
Wrote 0 new dynamic host decls to leases file.
Wrote 0 leases to leases file.
Listening on LPF/vmbr1/fa:98:02:e0:1c:28/192.168.0.0/27
Sending on   LPF/vmbr1/fa:98:02:e0:1c:28/192.168.0.0/27
Sending on   Socket/fallback/fallback-net
There's already a DHCP server running.

Hopefully I've included enough information to help aid in a resolution. Many thanks!

Solution

subnet 192.168.0.0 netmask 255.255.255.224 {
....
      host 104 {hardware ethernet 1A:27:59:82:39:8E;fixed-address 95.141.36.124;}
}

THe IP address (95.141.36.124) you want to associate to that MAC address is out of the range you defined (192.168.0.1 to 192.168.0.30)

If I set a similar config (fixed address out of range) at home, then the requests from the associated MAC address are ignored.

Try removing completly the entry, your host 104 should then got a dynmaic address from the 192.168.0.0/27 range

Comments

[eyoung100]

What "other server" is running?? There's already a DHCP server running.

[Joel Kennedy]

@ECarterYoung That's the actual DHCP server I've setup and have a problem with I think. The 'dhcpd' command would usually start the server, the server was already running as I had started it already so I just used the command to show the output information.

[Joel Kennedy]

I've just tried disabling iptables but no luck I'm afraid. There's no other firewall enabled on the system.