19c rac安装前提条件检查报反向路由没有正确设置

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rp_filter （Reverse Path Filtering）参数定义了网卡对接收到的数据包进行反向路由验证的规则。他有三个值，0、1、2，具体含意如下：

• 0：关闭反向路由校验
• 1：开启严格的反向路由校验。对每个进来的数据包，校验其反向路由是否是最佳路由。如果反向路由不是最佳路由，则直接丢弃该数据包。
• 2：开启松散的反向路由校验。对每个进来的数据包，校验其源地址是否可达，即反向路由是否能通（通过任意网口），如果反向路径不通，则直接丢弃该数据包。
  

什么是反向路由校验

所谓反向路由校验，就是在一个网卡收到数据包后，把源地址和目标地址对调后查找路由出口，从而得到反身后路由出口。然后根据反向路由出口进行过滤。

当rp_filter的值为1时，要求反向路由的出口必须与数据包的入口网卡是同一块，否则就会丢弃数据包。
当rp_filter的值为2时，要求反向路由必须是可达的，如果反路由不可达，则会丢弃数据包。

rp_filter的配置项

rp_filter是Linux的内核参数，可以针对每个网卡进行配置

在19C RAC安装时，如果有多个私网网卡，需要设置这个，在 /etc/sysctl.conf

net.ipv4.conf.eth0.rp_filter = 1

net.ipv4.conf.eth1.rp_filter = 2

net.ipv4.conf.eth2.rp_filter = 2

具体参加官方文档：

https://docs.oracle.com/database/121/CWLIN/networks.htm#CWLIN481

5.14 Multiple Private Interconnects and Oracle Linux

With Oracle Linux kernel 2.6.31, which also includes Oracle Unbreakable Enterprise Kernel 2.6.32, a bug has been fixed in the Reverse Path Filtering. As a consequence of this correction, Oracle RAC systems that use multiple NICs for the private interconnect now require specific settings for the rp_filter parameter. This requirement also applies to all Exadata systems that are running Linux kernel 2.6.32 and above. Without these rp_filter parameter settings systems, interconnect packets can be blocked or discarded.

The rp_filter values set the Reverse Path filter to no filtering (0), to strict filtering (1), or to loose filtering (2). Set the rp_filter value for the private interconnects to either 0 or 2. Setting the private interconnect NIC to 1 can cause connection issues on the private interconnect. It is not considered unsafe to disable or relax this filtering, because the private interconnect should be on a private and isolated network.

For example, where eth1 and eth2 are the private interconnect NICs, and eth0 is the public network NIC, set the rp_filter of the private address to 2 (loose filtering), the public address to 1 (strict filtering), using the following entries in /etc/sysctl.conf:

net.ipv4.conf.eth2.rp_filter = 2net.ipv4.conf.eth1.rp_filter = 2net.ipv4.conf.eth0.rp_filter = 1