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 = NIC alias =
 * 一つの物理NICに複数のIPを割り当てる
 == CentOS ==
 * [http://quox.org/tips/linux/redhat.html#net-ipalias Tips Collection - Red Hat Linux]

 === 設定 ===
 * /etc/sysconfig/network-scripts/
   * ifcfg-eth?:? を作る
   * 書式は通常の ifcfg-eth? と同じ
   * 例
     * dhcp (後述)
{{{
DEVICE=eth0:0
BOOTPROTO=dhcp
ONBOOT=yes
DHCP_HOSTNAME=centos5-test
}}}
     * static
{{{
DEVICE=eth0:0
BOOTPROTO=static
IPADDR=192.168.40.250
NETMASK=255.255.255.0
GATEWAY=192.168.40.2
ONBOOT=yes
DHCP_HOSTNAME=centos5-test
}}}
 * ifconfig (static)
{{{
eth0      Link encap:Ethernet  HWaddr 00:0C:29:XX:XX:XX
          inet addr:192.168.40.141  Bcast:192.168.40.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:102642 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1738 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:11384683 (10.8 MiB)  TX bytes:234313 (228.8 KiB)
          Interrupt:59 Base address:0x2000

eth0:0    Link encap:Ethernet  HWaddr 00:0C:29:XX:XX:XX
          inet addr:192.168.40.250  Bcast:192.168.40.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:59 Base address:0x2000
}}}

 === dhcpについて ===
 * 以下の問題は、BOOTPROTO=static の際には発生しない模様

 * ifup eth0:0 でエラーが出る
{{{
Determining IP information for eth0:0...SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
 done.
}}}
 * IP自体は正常にassignされる
   * ifconfig
{{{
eth0      Link encap:Ethernet  HWaddr 00:0C:29:XX:XX:XX
          inet addr:192.168.40.141  Bcast:192.168.40.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:102862 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1939 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:11403063 (10.8 MiB)  TX bytes:260163 (254.0 KiB)
          Interrupt:59 Base address:0x2000

eth0:0    Link encap:Ethernet  HWaddr 00:0C:29:XX:XX:XX
          inet addr:192.168.40.142  Bcast:192.168.40.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:59 Base address:0x2000
}}}
 * boot時のエラー
   * attachment:centos-alias.png
 * IPもassignされず
   * fconfig eth0:0
{{{
eth0:0    Link encap:Ethernet  HWaddr 00:0C:29:XX:XX:XX
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:59 Base address:0x2000
}}}
 * ifup eth0:0
{{{
Determining IP information for eth0:0...SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
SIOCGIFADDR: Cannot assign requested address
SIOCSIFBROADCAST: Cannot assign requested address
SIOCSIFBRDADDR: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
 done.
}}}
   * assignされず
 * ifup eth0:0
{{{
Determining IP information for eth0:0...SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
SIOCSIFFLAGS: Cannot assign requested address
 done.
}}}
   * assignされた
     * ifconfig eth0:0
{{{
eth0:0    Link encap:Ethernet  HWaddr 00:0C:29:XX:XX:XX
          inet addr:192.168.40.141  Bcast:192.168.40.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:59 Base address:0x2000
}}}

 * assignされたりされなかったりするため、不安定