当来自同一个MAC的两个请求时，我如何防止ISC-DHCPD提供不同的is？

Question

我有一组从ISC-DHCPD获取地址的节点。由于它们使用PXE启动，将有两轮DHCP (一次来自PXE，一次来自操作系统)，并且由于某种原因，ISC-DHCPD将提供两个不同的IP。这是不好的，因为节点的数目应该对应于ip的最后一个字节。

下面是Syslog的摘录，展示了正在发生的事情：

May 25 23:16:26 cluster dhcpd: DHCPDISCOVER from 08:00:27:d3:d5:3b via eth1
May 25 23:16:27 cluster dhcpd: DHCPOFFER on 192.168.0.1 to 08:00:27:d3:d5:3b via eth1
May 25 23:16:29 cluster dhcpd: DHCPREQUEST for 192.168.0.1 (192.168.0.254) from 08:00:27:d3:d5:3b via eth1
May 25 23:16:29 cluster dhcpd: DHCPACK on 192.168.0.1 to 08:00:27:d3:d5:3b via eth1
May 25 23:17:07 cluster dhcpd: DHCPDISCOVER from 08:00:27:d3:d5:3b via eth1
May 25 23:17:08 cluster dhcpd: DHCPOFFER on 192.168.0.2 to 08:00:27:d3:d5:3b via eth1
May 25 23:17:08 cluster dhcpd: DHCPREQUEST for 192.168.0.2 (192.168.0.254) from 08:00:27:d3:d5:3b via eth1
May 25 23:17:08 cluster dhcpd: DHCPACK on 192.168.0.2 to 08:00:27:d3:d5:3b via eth1
May 25 23:17:08 cluster dhcpd: DHCPREQUEST for 192.168.0.2 (192.168.0.254) from 08:00:27:d3:d5:3b via eth1
May 25 23:17:08 cluster dhcpd: DHCPACK on 192.168.0.2 to 08:00:27:d3:d5:3b via eth1

以下是租约文件的相应摘录：

lease 192.168.0.1 {
  starts 1 2015/05/25 21:16:28;
  ends 5 2151/07/02 03:44:43;
  cltt 1 2015/05/25 21:16:28;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 08:00:27:d3:d5:3b;
  uid "\001\010\000'\323\325;";
}
lease 192.168.0.2 {
  starts 1 2015/05/25 21:17:08;
  ends 5 2151/07/02 03:45:23;
  cltt 1 2015/05/25 21:17:08;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 08:00:27:d3:d5:3b;
}
lease 192.168.0.2 {
  starts 1 2015/05/25 21:17:08;
  ends 5 2151/07/02 03:45:23;
  cltt 1 2015/05/25 21:17:08;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 08:00:27:d3:d5:3b;
}

这是dhcp服务器的配置：

ddns-update-style none;

default-lease-time -1;
max-lease-time -1;

authoritative;

allow booting;
allow bootp;
next-server 192.168.0.254;
filename "/pxelinux.0";

log-facility local7;

subnet 192.168.0.0 netmask 255.255.255.0 {

    range 192.168.0.1 192.168.0.253;
    interface eth1;
    option routers 192.168.0.254;
    option domain-name "cluster.hpc.org";
    option domain-name-servers 192.168.0.254;

}

Answer 1

您可以使用“忽略客户端-uids”标志来获得它。它包括在4.2.0版本的isc-dchpd中：

增加这一行：

忽略-客户端-uids为真；

     ignore-client-uids flag;

     If the ignore-client-uids statement is present and has a value of
     true or on, the UID for clients will not be recorded.  If this
     statement is not present or has a value of false or off, then client
     UIDs will be recorded.

Answer 2

试着做些像

ddns-update-style none;

# Client control
deny duplicates;
one-lease-per-client on;

# Lease authority
default-lease-time 3600;
min-lease-time 3600;
max-lease-time 21600;

authoritative;

allow booting;
allow bootp;
next-server 192.168.0.254;
filename "/pxelinux.0";

log-facility local7;

subnet 192.168.0.0 netmask 255.255.255.0 {

    range 192.168.0.1 192.168.0.253;
    interface eth1;
    option routers 192.168.0.254;
    option domain-name "cluster.hpc.org";
    option domain-name-servers 192.168.0.254;

}

拒绝重复；主机声明可以基于DHCP客户端标识符选项或基于客户端的网络硬件类型和MAC地址匹配客户端消息。如果使用MAC地址，主机声明将匹配任何客户端与该MAC地址-甚至客户端具有不同的客户标识符。这种情况通常不会发生，但当一台计算机上安装了多个操作系统时(例如，Microsoft和NetBSD或Linux )，这是可能的。重复标志告诉DHCP服务器，如果从与主机声明的MAC地址匹配的客户端接收到请求，则即使UID不相同，与该MAC地址匹配的任何其他租约也应由服务器丢弃。这违反了DHCP协议，但可以防止客户端标识符定期更改的客户端同时持有多个租约。默认情况下，允许重复。

资料来源

http://www.bctes.com/dhcpd.conf.5.html

http://www.xdracco.net/howto-configure-and-deploy-isc-dhcp-server/