ubuntu-16.04 – 我是否可以通过DHCP请求特定的IP地址而不拒绝DHCP服务器提供的其他地址？

send dhcp-requested-address 10.23.33.254;

请改用 lease block.从试验和错误中,dhclient.conf文件中忽略此配置块,但在leases文件中使用(默认为/var/lib/dh​​cp/dhclient.leases,除非用-lf覆盖,就像从NetworkManager运行时一样)

只需构建一个最小的租约文件,该文件具有过期的续订和重新绑定(以避免一些重试)但仍然是未来的过期日期(不会立即忘记它并立即尝试发现而不是请求,并且如果没有则使用此IP DHCP服务器完全回答).保持此文件不变,并在每次运行dhclient之前复制它.

这是一个来自我的stretch-amd64容器的最小文件,只要DHCP服务器(此处为dnsmasq)没有为此客户端设置的其他租约就可以工作.在运行dhclient之前,只需将其复制到租约文件中即可.

lease {
  interface "eth0";
  fixed-address 10.0.3.222;
  renew 0 2000/1/1 00:00:01;
  rebind 0 2000/01/01 00:00:01;
  expire 0 2038/1/1 00:00:01;
}

尝试使用服务器10.0.3.0/24并且不知道此客户端的LAN服务器的局域网：

# dhclient -v eth0
Internet Systems Consortium DHCP Client 4.3.5
copyright 2004-2016 Internet Systems Consortium.
All rights reserved.
For info,please visit https://www.isc.org/software/dhcp/

Listening on LPF/eth0/xx:xx:xx:xx:xx:xx
Sending on   LPF/eth0/xx:xx:xx:xx:xx:xx
Sending on   Socket/fallback
DHCPREQUEST of 10.0.3.222 on eth0 to 255.255.255.255 port 67
DHCPACK of 10.0.3.222 from 10.0.3.1
bound to 10.0.3.222 -- renewal in 1486 seconds.

新租约文件/var/lib/dh​​cp/dhclient.leases：

lease {
  interface "eth0";
  fixed-address 10.0.3.222;
  renew 6 2000/01/01 00:00:01;
  rebind 6 2000/01/01 00:00:01;
  expire never;
}
lease {
  interface "eth0";
  fixed-address 10.0.3.222;
  option subnet-mask 255.255.255.0;
  option routers 10.0.3.1;
  option dhcp-lease-time 3600;
  option dhcp-message-type 5;
  option domain-name-servers 10.0.3.1;
  option dhcp-server-identifier 10.0.3.1;
  option dhcp-renewal-time 1800;
  option broadcast-address 10.0.3.255;
  option dhcp-rebinding-time 3150;
  option host-name "stretch-amd64";
  renew 0 2017/10/29 19:57:41;
  rebind 0 2017/10/29 20:24:34;
  expire 0 2017/10/29 20:32:04;
}

在IP范围之外尝试：

Listening on LPF/eth0/xx:xx:xx:xx:xx:xx
Sending on   LPF/eth0/xx:xx:xx:xx:xx:xx
Sending on   Socket/fallback
DHCPREQUEST of 10.0.4.222 on eth0 to 255.255.255.255 port 67
DHCPREQUEST of 10.0.4.222 on eth0 to 255.255.255.255 port 67
DHCPdisCOVER on eth0 to 255.255.255.255 port 67 interval 4
DHCPREQUEST of 10.0.3.249 on eth0 to 255.255.255.255 port 67
DHCPOFFER of 10.0.3.249 from 10.0.3.1
DHCPACK of 10.0.3.249 from 10.0.3.1
bound to 10.0.3.249 -- renewal in 1411 seconds.

这个DHCP服务器似乎没有发送NAK,但无论如何我确信你明白了,它确实有效.

如果没有DHCP服务器,经过一段时间后,dhclient将配置IP,因为它在租约和daemonize中没有过期.如果没有其他选项(广播…),这将是/ 32,因为信息不可用.如果需要,在“模板”租约文件中添加其他值.这将是：

option subnet-mask 255.255.255.0;
option routers 10.0.3.1;
option domain-name-servers 10.0.3.1;
option broadcast-address 10.0.3.255;

在这种情况下运行dhclient时：

[…]

DHCPdisCOVER on eth0 to 255.255.255.255 port 67 interval 12
No DHCPOFFERS received.
Trying recorded lease 10.0.3.222
PING 10.0.3.1 (10.0.3.1) 56(84) bytes of data.

--- 10.0.3.1 ping statistics ---
1 packets transmitted,1 received,0% packet loss,time 0ms
rtt min/avg/max/mdev = 0.240/0.240/0.240/0.000 ms
bound: immediate renewal.
DHCPREQUEST of 10.0.3.222 on eth0 to 255.255.255.255 port 67
root@stretch-amd64:~#