2020.9.20 Third job iptables

1. Reject all hosts to ping the current host

iptables -A INPUT -p icmp --icmp-type 8 -j REJECT

2. This machine can access the HTTP service of other machines, but other machines cannot access this machine

iptables -A INPUT -p tcp --syn --dport 80 -j REJECT

3. When we find that there is a malicious ip ***, we can control it by setting rules on the firewall. So we can add the connlimit module to achieve maximum concurrency control. Please write the steps

# 限制每IP所能够发起并发连接数为8
iptables -A INPUT -m connlimit --connlimit-above 8 -j REJECT

4. Practice questions

Hosts on the Internet:

[root@centos6 ~]$hostname -I
192.168.1.128
[root@centos6 ~]$route -n 
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     1002   0        0 eth0
0.0.0.0         192.168.1.129   0.0.0.0         UG    0      0        0 eth0

Firewall:

[root@centos8 ~]$hostname -I
10.0.0.8 192.168.1.129
[root@centos8 ~]$route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.2        0.0.0.0         UG    100    0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
192.168.1.0     0.0.0.0         255.255.255.0   U     101    0        0 eth1
[root@centos8 ~]$cat /proc/sys/net/ipv4/ip_forward
1

LAN server:

[root@centos7 ~]$hostname -I
10.0.0.18
[root@centos7 ~]$route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.0.0.8        0.0.0.0         UG    0      0        0 eth0
10.0.0.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0