Network Security, Firewalls And Vpns

Front 1

What is a Firewall?

Back 1

Firewall is a device that is placed between a trusted and an untrusted network. It deny or permit traffic that enters or leaves network based on pre-configured policies.

Firewalls protect inside networks from unauthorized access by users on an outside network. A firewall can also protect inside networks from each other. For example - By keeping a Management network separate from a user network.

Front 2

What is the difference between Gateway and Firewall?

Back 2

A Gateway joins two networks together and a network firewall protects a network against unauthorized incoming or outgoing access. Network firewalls may be hardware devices or software programs.

Front 3

What is the difference between Stateful & Stateless Firewall?

Back 3

Stateful firewall - A Stateful firewall is aware of the connections that pass through it. It adds and maintains information about users connections in state table, referred to as a connection table. It than uses this connection table to implement the security policies for users connections. Example of stateful firewall are PIX, ASA, Checkpoint.

Stateless firewalls - (Packet Filtering) Stateless firewalls on the other hand, does not look at the state of connections but just at the packets themselves.Example of a packet filtering firewall is the Extended Access Control Lists on Cisco IOS Routers.

Front 4

What information does Stateful Firewall Maintains?

Back 4

Stateful firewall maintains following information in its State table:-

1.Source IP address.

2.Destination IP address.

3.IP protocol like TCP, UDP.

4.IP protocol information such as TCP/UDP Port Numbers, TCP Sequence Numbers, and TCP Flags.

Front 5

What are the security-levels in Cisco ASA?

Back 5

ASA uses Security levels to determine the Trustworthiness of a network attached to the respective interface. The security level can be configured between 0 to 100 where higher numbers are more trusted than lower. By default, the ASA allows traffic from a higher security level to a lower security level only.

Front 6

How can we allow packets from lower security level to higher security level (Override Security Levels)?

Back 6

We use ACLs to allow packets from lower security level to higher security level.

Front 7

Same Security level traffic is allowed or denied in ASA?

Back 7

By default same security level traffic is not allowed. To allow it we use command:-ASA(config)# same-security-traffic permit inter-interface.