What ofllowing line mean? -A RH-Firewall-l-INPUT -m state --state NEW -m tcp -p

Question

What ofllowing line mean? -A RH-Firewall-l-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT Explain ofllowing lines line by line? ddns-update-style interim; ignore client-updates; subnet 172.16.1.0 net mask 255.255.255.0 { option routers 172.16.1.1; option subnet-mask 255.255.255.0; option domain-name "csusbcoyote.net"; option domain-name servers 139.182.2.1, 139.182.2.6; option time-offset -28800; # Pacific Standard Time range dynamic-bootp 172.16.1.101 172.16.1.254; default-lease-time 21600; max-lease-time 43200;

Explanation / Answer

7) -A RH-Firewall-1-Input -m state --state NEW -m tcp -p -tcp --dport 22 -j ACCEPT

This is a firewall rule which is used to specify that All incoming ports are closed except the ports in Chain "RH-Firewal-1-INPUT"

this rule states that If the protocol is TCP and destination port is 22 and the state of connection is new then ACCEPT it.

8)

this statement is used to update the DNS scheme

There are two DNS update schemes are currently implemented — the ad-hoc DNS update mode and the interim DHCP-DNS interaction draft update mode. This is the later one. it allows to create the configuration file that stores the network information for the clients. we Use this file to declare options and global options for client systems.The configuration file can contain extra tabs or blank lines for easier formatting. Keywords are case-insensitive and lines beginning with a hash mark (#) are considered comments.

The next block

subnet {

}

is a subnet declaration that is a must to be included for every subnet in the network.

If it is not, the DHCP server fails to start.

In this, there are global options for every DHCP client in the subnet and a range declared. Clients are assigned an IP address within the range.

option domain-name text;

This option specifies the domain name that client should use when resolving hostnames via the Domain Name System.

option domain-name-servers 139.182.2.1 , 139.182.2.6 ;

The domain-name-servers option specifies a list of Domain Name System (STD 13, RFC 1035) name servers available to the client. Servers should be listed in order of preference

default-lease-time 21600;

= Default & max lease times: how long may a client keep an address until it needs to refresh it? Lowered to maked it easier to 6h/12h to make it easyer (faster) to manage addresses.

= Dynamically assigned addresses. These addresses will be used for machines not (yet) explicitly listed in this file.

= Subnet mask, sent to client

option time-offset -28800;

The time-offset option specifies the offset of the client's subnet in seconds from Coordinated Universal Time (UTC).

option routers 172.16.1.1;

The routers option specifies a list of IP addresses for routers on the client's subnet. Routers should be listed in order of preference.

  ddns-update-style interim;  

this statement is used to update the DNS scheme

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