Mid Sweden University
Dept. of IT and Media (ITM)
Magnus Eriksson
Email magnus.eriksson@miun.se
2013-01-31
Page 1 of 2
Network Technology I – Extra exercises on sub-netting
Host C
IP: 130.16.4.1
MAC: 015100212983
Host D
Host B
130.16.4.2
70DD35530178
Router
+ NAT
server
Privat IP: 10.14.5.2
MAC: 02CB239B
172.16.5.255
Private IP: 10.14.5.1
Public IP: 193.10.250.187
MAC addr: 0013020764AE
130.16.4.3
BB26165274D3
Host A
Router
Private IP: 10.2.1.1
Public IP: 193.10.250.187
MAC addr: 31BE4A19273A
10.2.1.2
193.10.250.187
A0C11222F53B
10.2.1.3
001B55301781
1. An evil spy has installed a sniffer software on host computer A as well as on host B, in
view to eavesdrop communication in the above network. Both sniffers detect an Ethernet
frame (including an IP datagram) sent from host D, and destined to host C. Note that
the right router includes a Network Address Translation (NAT) function, enabling
several computers to share the same public IP address. What IP source address and
destination address does the datagram have, and what physical source and destination
address does the Ethernet frame have,
a) according to the sniffer on host A?
b) according to the sniffer on host B?
2. Here follows two IP addresses. State for each of them what class they would belong to if
classful addressing were used (A/B/C/D/E), number of possible host adresses in the
network. Also state their network-ID, host ID, network address and the IP broadcast
address.
a) 00010000 00001010 10000000 000000012
b) 193.10.25.51
Exam in Computer Networks A 30 October 2006
Page 2
3. A router has the following routing table.
Destination
10.14.5.254
10.14.0.0
10.0.0.0
193.218.5.0
0.0.0.0 (=default)
Netmask
255.255.255.255
255.255.0.0
255.0.0.0
255.255.255.0
0.0.0.0
Next-hop
127.0.0.1
10.14.1.254
10.1.1.254
10.2.1.2
10.3.1.2
Interface
1
1
3
2
4
Metric
1
20
20
20
40
a) Where will a packet destined to address 10.14.1.105 be sent? (Which row matches,
starting from the one with the lowest metric, and to what next-hop and interface.)
b) Where will a packet destined to address 193.218.1.1 be sent?
c) How many host computers can a packet destined to address 10.14.255.255 maximum
reach? What is the first and last IP address of the series?
4. Consider the IP address of 182.133.129.55.
a) What is the class of this network if classful addressing was used? How many bit long
is the network-ID if classful addressing was used? What is the network ID and host-ID of
our computer? What is the default network mask? How many network hosts (computers)
can be addressed in this network?
b) Assume that this network is divided into subnets using the subnet mask
255.255. 252.0. How many bit long are the subnet-ID and the host-ID?
c) What is the new host-ID of our host?
d) What is the broadcasting address of this subnet?
e) How many network hosts can be connected to this subnet?
f) How many subnets is the the network devided into? (Do not use subnet 0 and the last
subnet, in view to avoid confusion of the subnet broadcast address and the network
broadcast address, and also to avoid confusion between the subnet address and the
network address.)
5. You have got the addrress area 195.15.40.0/24 (that is original network mask
255.255.255.0). Divide this network into 3 subnets of different number of hosts,
accoding to the topolog below. State the network addres, subnet mask and broadcast
address of each subnet.
(4 p)