Gate 2011 : Layer 4 firewall

[mayank]

A layer-4 firewall CANNOT :

(a) block entire http traffic during 9:00 pm and 5:00 am.

(b) block all ICMP traffic. 

(c) stop incoming traffic from a specific IP address but allow outgoing traffic to the same IP address.

(d) block TCP traffic from a specific user on a multiuser system during 9:00 pm and 5:00 am.

In this question no option is correct becoz at TL by blocking TCP segments with port no. 80, We can block http. So are we correct..??

[Ravi]

Option d says specific host..in order to block specific host, we definitely need to have password and authentication..so we need application layer :)

[mayank]

but this can also  be done by putting restriction on the ip address of a particular user . 

[Ravi]

Ip address changes in seconds :)

[mayank]

but if a permanent ip is given he can be blocked

[Ravi]

how can you get a permanent IP...IANA teri gf ka company hai kya..

[paresh nemade]

@mayank even if you assign IP address to a machine(private address) it
changes when this machine gets connected to the Internet. NAT
(network address translation ) is done whenever packer crosses
organization boundary

[Sajal Sharma]

even if you block a particular IP address of that particular user,then that IP will be blocked,but doing so will block all the users that try to login from that IP address which we dont want to do.....