简单说明
tcp套接字支持md5选项，通过设置套接字的md5选项，在该套接字上发送报文时会添加md5摘要选项内容。接收端在收到报文后，对md5值进行校验。如果不能通过校验，则拒绝接收，这些都是在tcp层负责处理，有一定的性能损耗。
实验topo
实验说明：设置RTA和RTB彼此为邻居，使用neighbor xxx password xxx命令为两者设置密钥，当密钥相同时，可以成功建立邻居关系，反之不能成功建立邻居。
实验配置
RTA
Building configuration...
Current configuration:
!
frr version 7.1
frr defaults traditional
hostname 486cd3e0f81f
log syslog informational
no ipv6 forwarding
hostname RTA
service integrated-vtysh-config
!
router bgp 65001
neighbor 10.1.1.2 remote-as external
!
line vty
!
end
RTA#
RTB
Building configuration...
Current configuration:
!
frr version 7.1
frr defaults traditional
hostname a86b8fff04c7
log syslog informational
no ipv6 forwarding
hostname RTB
service integrated-vtysh-config
!
router bgp 65002
neighbor 10.1.1.1 remote-as external
!
line vty
!
end
RTB#
查看邻居
RTA# show bgp neighbors 10.1.1.2
BGP neighbor is 10.1.1.2, remote AS 65002, local AS 65001, external link
Hostname: a86b8fff04c7
BGP version 4, remote router ID 172.17.0.3, local router ID 172.17.0.2
BGP state = Established, up for 00:02:33
可以看到邻居已经正常建立。
给RTA配置密钥
RTA(config-router)# neighbor 10.1.1.2 password test
RTA(config-router)#
#查看邻居
RTA# show bgp neighbors 10.1.1.2
BGP neighbor is 10.1.1.2, remote AS 65002, local AS 65001, external link
Hostname: a86b8fff04c7
BGP version 4, remote router ID 0.0.0.0, local router ID 172.17.0.2
BGP state = Connect
Last read 00:00:53, Last write 00:00:53
Hold time is 180, keepalive interval is 60 seconds
#从上面可以看出，邻居处于connect状态了，邻居被断开了。
给RTB也配置相同的秘钥
RTB(config-router)# neighbor 10.1.1.1 password test
RTB(config-router)#
# 查看邻居
RTB# show bgp neighbors
BGP neighbor is 10.1.1.1, remote AS 65001, local AS 65002, external link
Hostname: 486cd3e0f81f
BGP version 4, remote router ID 172.17.0.2, local router ID 172.17.0.3
BGP state = Established, up for 00:00:02
Last read 00:00:01, Last write 00:00:01
Hold time is 180, keepalive interval is 60 seconds
Neighbor capabilities:
将RTB的秘钥配置成与RTA不同
RTB(config-router)# neighbor 10.1.1.1 password test1
RTB(config-router)#
# 查看邻居
RTB# show bgp neighbors
BGP neighbor is 10.1.1.1, remote AS 65001, local AS 65002, external link
Hostname: 486cd3e0f81f
BGP version 4, remote router ID 0.0.0.0, local router ID 172.17.0.3
BGP state = Connect
Last read 00:00:25, Last write 00:00:25
Hold time is 180, keepalive interval is 60 seconds
Message statistics: