DHCPd

• 標準はISC DHCPd
• Ubuntuでは「udhcpd」という組み込み機器向け由来のDHCPdも選択できる。

• ​jman:dhcpd.conf
• ​man:5:dhcpd.conf

logging

• log-facility でsyslogへのログ出力を変更できる
• Ubuntu:/etc/dhcp3/dhcpd.conf

  # Use this to send dhcp log messages to a different log file (you also
  # have to hack syslog.conf to complete the redirection).
  log-facility local7;
  

• syslog.conf

  local7.* -/var/log/dhcpd.log
  

• CentOSでは、local7はデフォルトでbootログ用に使われているようなので、変えた方が良いかもしれない。
  • /etc/syslog.conf

    # Save boot messages also to boot.log
    local7.*                                                /var/log/boot.log
    

  • /var/log/boot.log

    Jul  1 16:43:03 VM-centos5 NET[3471]: /sbin/dhclient-script : updated /etc/resolv.conf
    Jul  1 16:43:08 VM-centos5 NET[3562]: /sbin/dhclient-script : updated /etc/resolv.conf
    Jul  1 16:47:13 VM-centos5 NET[3692]: /sbin/dhclient-script : updated /etc/resolv.conf
    (snip)
    

Ubuntu

• aptitude install dhcp3-server
  • clientは標準ではdhcp3-client

configure

• /etc/default/dhcp3-server

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

  • ListenするIFを指定
• /etc/dhcp3/dhcpd.conf についてはman dhcpd.conf

warning with dhcp3

• ​Bug #39249 in dhcp3 (Ubuntu): “(Dapper, Hardy) can't create /var/lib/dhcp3/dhclient.eth0.leases: Permission denied”
  • sudo chown dhcp:dhcp /var/lib/dhcp3/

CentOS

• yum install dhcp
  • clientは標準ではdhclient

configure

• /etc/sysconfig/dhcpd

  # Command line options here
  DHCPDARGS=
  

• /etc/dhcpd.conf についてはman dhcpd.conf

searching multiple domains

• ​setting the DNS search string

  option domain-search domain-list;

  This was added in 3.1.0.
  (snip)
  You can configure 'option domain-name "example.com sales.example.com";', and on many Unixish systems, this will become a 'search' string in /etc/resolv.conf. But it doesn't work as expected on many non-unixish systems (they parse the spaces as part of the domain name).

• ​DNS クライアントでのドメイン サフィックス検索一覧の設定方法

  DHCP (Dynamic Host Configuration Protocol)。ドメイン サフィックス検索一覧を送信するように DHCP を構成することはできません。これは DHCP プロトコル自体の制限であり、特定のベンダの DHCP 実装の制限によるものではありません。

• ​How to request domain-search option from DHCP server ?

  I don't believe it's supported, because the DHCP server will only give an option if the option was requested by the DHCP client. So it appears that would need additional configuration on the client side such as the option.

multiple domain-name on same subnet

• Debian GNU/Linux 6.0.4 (squeeze)

• ドメインはlocal.mitty.jpとdhcp.mitty.jp
  • local -> static assign
  • dhcp -> dynamic assign
• host {...} で定義されたものがlocalに、それ以外はdhcpへ
• /23のサブネットを用いて、localとdhcpで192.168.0.0と192.168.0.1に分ける
  • 普通に/24 x 2個のサブネットにしてしまうと、local<->dhcp間のデータがdefault routeで中継されてしまいうまくない

• /etc/dhcp/dhcpd.conf

  ddns-update-style interim;
  
  option domain-name "dhcp.mitty.jp";
  option domain-name-servers 192.168.0.254;
  
  default-lease-time 172800;
  max-lease-time 2678400;
  
  authoritative;
  
  log-facility local7;
  
  subnet 192.168.0.0 netmask 255.255.254.0 {
  	option routers 192.168.0.254;
  	option ntp-servers 192.168.0.254;
  	option broadcast-address 192.168.0.255;
  	option domain-search "local.mitty.jp", "dhcp.mitty.jp";
  	
  	pool {
  		allow unknown-clients;
  		option domain-name "dhcp.mitty.jp";
  		range 192.168.1.100 192.168.1.199;
  		default-lease-time 7200;
  		max-lease-time 86400;
  		ddns-updates on;
  	}
  	
  	pool {
  		deny unknown-clients;
  		option domain-name "local.mitty.jp";
  		range 192.168.0.100 192.168.0.199;
  		ddns-updates off;
  	}
  	
  	include "/etc/dhcp/dhcpd.conf.d/local.mitty.jp";
  }
  

  • poolを使って、allow/deny unknown-clientsで選別する

    The unknown-clients flag is used to tell dhcpd whether or not to dynamically assign addresses to unknown clients. Dynamic address assignment to unknown clients is allowed by default. An unknown client is simply a client that has no host declaration.