WordPress开启多站点，完成设置添加完站点之后，打开新添加的站点后台管理页面（仪表盘）时出现404错误。
注：WordPress版本 6.6.1 ，多站点配置为子目录形式， IIS版本10。
研究发现，在配置站点网络过程中WordPress生成的web.config代码有错误：
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name="WordPress Rule 1" stopProcessing="true">
<match url="^index\.php$" ignoreCase="false" />
<action type="None" />
</rule>
<rule name="WordPress Rule 2" stopProcessing="true">
<match url="^([_0-9a-zA-Z-]+/)?wp-admin$" ignoreCase="false" />
<action type="Redirect" url="{R:1}wp-admin/" redirectType="Permanent" />
</rule>
<rule name="WordPress Rule 3" stopProcessing="true">
<match url="^" ignoreCase="false" />
<conditions logicalGrouping="MatchAny">
<add input="{REQUEST_FILENAME}" matchType="IsFile" ignoreCase="false" />
<add input="{REQUEST_FILENAME}" matchType="IsDirectory" ignoreCase="false" />
</conditions>
<action type="None" />
</rule>
<rule name="WordPress Rule 4" stopProcessing="true">
<match url="^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*)" ignoreCase="false" />
<action type="Rewrite" url="{R:1}" />
</rule>
<rule name="WordPress Rule 5" stopProcessing="true">
<match url="^([_0-9a-zA-Z-]+/)?([_0-9a-zA-Z-]+/)?(.*\.php)$" ignoreCase="false" />
<action type="Rewrite" url="{R:2}" />
</rule>
<rule name="WordPress Rule 6" stopProcessing="true">
<match url="." ignoreCase="false" />
<action type="Rewrite" url="index.php" />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>
其中第四条WordPress Rule 4重写规则中的反向引用{R:1}有误，应改为{R:2}。
WordPress官方文档中关于此配置的相关内容如下：
WordPress >=3.5 Subfolder Example
# BEGIN WordPress Multisite
# Using subfolder network type: https://wordpress.org/documentation/article/htaccess/#multisite
RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]
# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
# END WordPress Multisite
可以看到，文档中关于此条重写规则的反向引用确实为 $2，即IIS下的 {R:2}
修改后问题解决，记录一下。