想整两台小主机，异地组网，结果硬件价格越来越贵，目标转向路由器。
难点
焊接ttl to usb模块
闪存坏块
使用breed刷入固件时报错
breed> mt7621-nfi.0: Skip bad block at 0x00920000 (BA 0x49).
mt7621-nfi.0: Skip bad block at 0x00b20000 (BA 0x59).
mt7621-nfi.0: Skip bad block at 0x00920000 (BA 0x49).
mt7621-nfi.0: Skip bad block at 0x00b20000 (BA 0x59).
mt7621-nfi.0: Skip bad block at 0x00920000 (BA 0x49).
Error: erase operation failed at 0x00140000, size 0xe40000
校验失败,请重试!
解决办法：
- PB-boot
- 先刷小体积固件，再使用内置升级工具升级
遇到的坑
重启丢配置
解决方法：看看自己用的固件是不是initramfs-kernel，此类版本基本用于测试，重启丢配置。
可尝试刷入squashfs-factory或squashfs-sysupgrade
但是我在刷入squashfs-factory时提示坏块，大概是因为这个固件体积稍大。迫不得已，只能先刷入initramfs-kernel，之后ssh链接此路由器，执行sysupgrade -p squashfs-sysupgrade固件的名字.bin解决重启丢配置的问题。此处感谢网友@theNew0rder
opkg之ssl安装死循环
安装luci-app-clash时提示已经存在 libustream-wolfssl20201210，不能安装libustream-openssl
就报错。
遂卸载libustream-wolfssl20201210，重新安装luci-app-clash，但是报错本机没有ssl包
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
Collected errors:
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/base/libustream-openssl20201210_2020-12-10-68d09243-1_mipsel_24kc.ipk, wget returned 1
* opkg_install_pkg: Failed to download libustream-openssl20201210. Perhaps you need to run 'opkg update'?
* opkg_install_cmd: Cannot install package luci-app-clash.
根据提示，更新缓存，又报错
root@ZTE-E8820S-1:/tmp# opkg update
Downloading https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/targets/ramips/mt7621/packages/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/targets/ramips/mt7621/packages/Packages.gz
Downloading https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/base/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/base/Packages.gz
Downloading https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/luci/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/luci/Packages.gz
Downloading https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/packages/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/packages/Packages.gz
Downloading https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/routing/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/routing/Packages.gz
Downloading https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/telephony/Packages.gz
wget: SSL support not available, please install one of the libustream-.*[ssl|tls] packages as well as the ca-bundle and ca-certificates packages.
*** Failed to download the package list from https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/telephony/Packages.gz
Collected errors:
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/targets/ramips/mt7621/packages/Packages.gz, wget returned 1.
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/base/Packages.gz, wget returned 1.
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/luci/Packages.gz, wget returned 1.
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/packages/Packages.gz, wget returned 1.
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/routing/Packages.gz, wget returned 1.
* opkg_download: Failed to download https://mirrors.tuna.tsinghua.edu.cn/openwrt/releases/21.02.0-rc4/packages/mipsel_24kc/telephony/Packages.gz, wget returned 1.
好在修改连接协议https为http解决
动态DNS
修改完配置，记得点击保存并应用。
网络防火墙
不能直接service iptables save。只能将iptables命令保存在/etc/firewall.user
使用lan口对外提供服务，设置较严格的过滤规则。
但记得要同时允许DHCP流量进入。