VirtualBox上でNICを追加、
普通に自動認識しないので
設定変更です。

覚書
http://d.hatena.ne.jp/iww/20080826/deb

おそらくは起動時に読込むルールであろうファイルを
削除です。
----------------------------------------
debian:/home/tmp#
debian:/home/tmp# rm -rf /etc/udev/rules.d/z25_persistent-net.rules
debian:/home/tmp#
----------------------------------------

ネットワーク設定ファイルを変更、
eth0をdhcpクライアントモードに修正し
#2ndより後にeth1の設定を追加です。
(#の行はコメント)
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debian:/home/tmp#
debian:/home/tmp# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
iface eth0 inet dhcp

#2nd
allow-hotplug eth1
iface eth1 inet static
address 10.0.3.100
network 10.0.3.0
netmask 255.255.0.0
broadcast 10.0.3.255
gateway 10.0.2.2
debian:/home/tmp#
----------------------------------------

当然、resolve.confも
VirtualBoxNATクライアント用に変更。
----------------------------------------
debian:/home/tmp#
debian:/home/tmp# cat /etc/resolv.conf
nameserver 10.0.2.3
debian:/home/tmp#
----------------------------------------

/etc/init.d restartで上手く動かない為、
reboot、設定変更完成です、
ネットワーク動作試験はこちら。
----------------------------------------
debian:/home/tmp#
debian:/home/tmp# ifconfig
eth0      Link encap:Ethernet  HWaddr 08:00:27:5B:27:51
          inet addr:10.0.2.15  Bcast:10.0.2.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe5b:2751/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:79 errors:0 dropped:0 overruns:0 frame:0
          TX packets:59 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:8199 (8.0 KiB)  TX bytes:8049 (7.8 KiB)
          Interrupt:11 Base address:0xc020

eth1      Link encap:Ethernet  HWaddr 08:00:27:88:32:70
          inet addr:10.0.3.100  Bcast:10.0.3.255  Mask:255.255.0.0
          inet6 addr: fe80::a00:27ff:fe88:3270/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:594 (594.0 b)
          Interrupt:10 Base address:0xc240

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:9 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:640 (640.0 b)  TX bytes:640 (640.0 b)

debian:/home/tmp#
----------------------------------------

おまけ
工数的には仮想ネットワーク構築も含め
5時間と言った所でしょうか・・・。