首先是安裝Ubuntu 20.04 LTS Server,這個步驟網上都可以找到

注意的是，安裝的時候開啟openssh-server

下述步驟是是指定安裝好Ubuntu 20.04 LTS Server後

推薦先修改源為aliyun源

sudo mv /etc/apt/sources.list /etc/apt/sources.list.bak
sudo vi /etc/apt/sources.list

寫入以下內容

deb https://mirrors.aliyun.com/ubuntu focal main restricted
deb https://mirrors.aliyun.com/ubuntu focal-updates main restricted
deb https://mirrors.aliyun.com/ubuntu focal universe
deb https://mirrors.aliyun.com/ubuntu focal-updates universe
deb https://mirrors.aliyun.com/ubuntu focal multiverse
deb https://mirrors.aliyun.com/ubuntu focal-updates multiverse
deb https://mirrors.aliyun.com/ubuntu focal-backports main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu focal-security main restricted
deb https://mirrors.aliyun.com/ubuntu focal-security universe
deb https://mirrors.aliyun.com/ubuntu focal-security multiverse

並儲存後，執行audo apt update

1.安裝net-tools( ifconfig命令可用）

sudo apt install net-tools

安裝後就可以檢視網路卡資訊，ifconfig -a

2.修改網路卡名enp2s0,enp3s0（每個人可能不一樣）為eth0,eth1等

sudo vi /etc/default/grub

修改GRUB_CMDLINE_LINUX=""為GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0"

sudo grub-mkconfig -o /boot/grub/grub.cfg

修改這裡面的/etc/netplan/00-installer-config.yaml， 沒有修改會導致下次開機後無法上網。

將enp2s0修改為eth0, 修改enp3s0修改為eth1

後續把eth0作為wan，把eth1作lan

重啟， sudo reboot now 

3.配置網路卡地址，lan設定為靜態ip

修改/etc/netplan/00-installer-config.yaml, 參考以下內容修改

network:
  ethernets:
    eth0:
      dhcp4: true
    eth1:
      dhcp4: false
      addresses: 
      - 192.168.99.1/24
  version: 2

sudo netplan apply 使配置生效

4.配置dhcp

sudo apt  install isc-dhcp-server

aa.修改配置檔案/etc/default/isc-dhcp-server

INTERFACESv4=""
INTERFACESv6=""

修改成

INTERFACESv4="eth1"
INTERFACESv6="eth1"

bb.修改/etc/dhcp/dhcpd.conf

option domain-name-servers ns1.example.org, ns2.example.org;

修改成

option domain-name-servers 8.8.8.8,114.114.114.114;

並末尾增加以下內容

subnet 192.168.99.0 netmask 255.255.255.0 {
  range 192.168.99.100 192.168.99.254;
  option domain-name-servers 192.168.99.1;
  option subnet-mask 255.255.255.0;
  option broadcast-address 192.168.99.255;
  option routers 192.168.99.1;
}

cc.修改/etc/dhcp/dhcpd6.conf

末尾增加以下內容

subnet6 2001:db8:0:1::/64 {
        # Range for clients
        range6 2001:db8:0:1::129 2001:db8:0:1::254;

        # Range for clients requesting a temporary address
        range6 2001:db8:0:1::/64 temporary;

        # Additional options
        option dhcp6.name-servers fec0:0:0:1::1;
        option dhcp6.domain-search "domain.example";

        # Prefix range for delegation to sub-routers
        prefix6 2001:db8:0:100:: 2001:db8:0:f00:: /56;

        # Example for a fixed host address
        host specialclient {
                host-identifier option dhcp6.client-id 00:01:00:01:4a:1f:ba:e3:60:b9:1f:01:23:45;
                fixed-address6 2001:db8:0:1::127;
        }
}  

重啟dhcp server

sudo systemctl start isc-dhcp-server #啟動dhcp server

sudo systemctl status isc-dhcp-server #檢視啟動狀態

5.配置防火牆

sudo ufw allow 22 #允許ssh訪問

sudo ufw logging on

修改/etc/default/ufw

DEFAULT_FORWARD_POLICY="DROP"

修改為

DEFAULT_FORWARD_POLICY="ACCEPT"

修改/etc/sysctl.conf

#net.ipv4.ip_forward=1
修改為
net.ipv4.ip_forward=1

sudo sysctl -p生效

修改/etc/ufw/before.rules檔案，

在loopback之後，增加eth1（紅色那部分內容）

# allow all on loopback
-A ufw-before-input -i lo -j ACCEPT
-A ufw-before-output -o lo -j ACCEPT

# allow all on lan, eth1
-A ufw-before-input -i eth1 -j ACCEPT
-A ufw-before-output -o eth1 -j ACCEPT

同時

在“# Don't delete these required lines, otherwise there will be errors
*filter
:ufw-before-input - [0:0]”之前增加以下內容

*nat
:POSTROUTING ACCEPT [0:0]

# Forward traffic through eth0 - Change to match you out-interface
-A POSTROUTING -s 192.168.99.0/24 -o eth0 -j MASQUERADE

# don't delete the 'COMMIT' line or these nat table rules won't
# be processed
COMMIT

修改後,重啟ufw

sudo ufw disable

sudo ufw enable

6.配置dns

停用系統自帶dns

sudo systemctl disable systemd-resolved

sudo systemctl stop systemd-resolved

刪除符號連結的resolv.conf檔案

sudo rm /etc/resolv.conf

echo "nameserver 8.8.8.8" > /etc/resolv.conf

安裝dnsmasq

sudo apt-get install dnsmasq

sudo service isc-dhcp-server restart

正常情況下，客戶機電腦可以通過eth1自動獲取ip和dns

 

7.pppoe撥號上網

sudo apt install pppoeconf

貓網線連線到eth0, 執行 pppoeconf開始自動配置撥號相關引數，需要知道撥號賬號和密碼

撥號成功後，軟路由可以上網。

可能遇到客戶機上不了網

修改/etc/ufw/before.rules檔案中的網路卡，因為撥號後網路卡是ppp0, 如果是自動上網方式則使用eth0

將-A POSTROUTING -s 192.168.99.0/24 -o eth0 -j MASQUERADE修改為-A POSTROUTING -s 192.168.99.0/24 -o ppp0 -j MASQUERADE

 

8.miniupnpd配置

upnp是p2p一類軟體需要的，需要穿透firewall

sudo apt install miniupnpd

配置是外網是撥號則ppp0，外網是靜態或是dhcp的則eth0

內網是eth1