lab3-report - Heyook

droppercauseNetworking and Communications

Oct 28, 2013 (3 years and 9 months ago)

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Prelab:

1.)

mtu <64
-
18000> (size in bytes)


2.)

The router sends an ARP request to the destination host, if

there is an ARP reply then the host is available. If not, continue to

forward according to routing table.


3.)

Routers.


4.)

30 hops which is the sa
me default used for TCP connections.


5.)

The role of the default gateway is to provide the next
-
hop IP

address and interface for all destinations that are not located on its

subnet. Without a default gateway, communication with remote

destination

is not
possible unless additional routes are added to the IP routing

table.


6.)

192.110.50.0


7.)

Network IP address is the (host ip && subnet mask), and the

network prefix is the first N bits of (host ip && subnet mask), where N

is given by xxx.xxx.xxx.xxx/N.


8.)

1092 networks. The maximum number of hosts for the whole network

number is 2^(32
-
16) = 2^16 = 65536. And there needs to be 60 hosts on

each network so you divide 65536/60 = 1092.


Ex1

What is the output on PC1


when the ping command are issued:

ping

c

5 10.0.1.21

PING 10.0.1.21 (10.0.1.21) 56(84) bytes of data.

64 bytes from 10.0.1.21: icmp_seq=1 ttl=64 time=0.585 ms

64 bytes from 10.0.1.21: icmp_seq=2 ttl=64 time=0.294 ms

64 bytes from 10.0.1.21: icmp_seq=3 ttl=64 time=0.308 ms

64 bytes from 10.0.1.21
: icmp_seq=4 ttl=64 time=0.382 ms

64 bytes from 10.0.1.21: icmp_seq=5 ttl=64 time=0.299 ms


---

10.0.1.21 ping statistics
---

5 packets transmitted, 5 received, 0% packet loss, time 4022ms

rtt min/avg/max/mdev = 0.294/0.373/0.585/0.112 ms

ping

c 5 10.0.2.
1

connect: Network is unreachable

ping

c 5 10.0.3.41

connect: Network is unreachable


Which packets, if any, are captured by ethereal?

ARP and ICMP packets


Do you observe any ARP or ICMP packets? If so, what do they indicate.

ARP: PC1 broadcasts an ARP p
ackets requesting the MAC of PC2 which has IP 10.0.1.21. Then
PC2 sends an ARP reply saying that the MAC of 10.0.1.21(itself) is at 00:50:bf:75:23:bb


1 0.000000 00:04:75:ac:88:a5 ff:ff:ff:ff:ff:ff ARP Who has 10.0.1.21? Tell 10.0.1.1
1


2 0.000216 00:50:bf:75:23:bb 00:04:75:ac:88:a5 ARP 10.0.1.21 is at
00:50:bf:75:23:bb

ICMP: 5 ICMP requests and 5 ICMP reply correspond to 5 pings issued by PC1


3 0.000235 10.0.1.11 10.0.1.21 ICMP

Echo (ping) request


4 0.000556 10.0.1.21 10.0.1.11 ICMP Echo (ping) reply


5 1.020803 10.0.1.11 10.0.1.21 ICMP Echo (ping) request


6 1.021078 10.0.1.21 10.0.1.11

ICMP Echo (ping) reply


7 2.021338 10.0.1.11 10.0.1.21 ICMP Echo (ping) request


8 2.021627 10.0.1.21 10.0.1.11 ICMP Echo (ping) reply


9 3.021414 10.0.1.11

10.0.1.21 ICMP Echo (ping) request


10 3.021770 10.0.1.21 10.0.1.11 ICMP Echo (ping) reply


11 4.022816 10.0.1.11 10.0.1.21 ICMP Echo (ping) request


12 4.0
23097 10.0.1.21 10.0.1.11 ICMP Echo (ping) reply

ARP: confirmation


13 4.991559 00:50:bf:75:23:bb 00:04:75:ac:88:a5 ARP Who has 10.0.1.11? Tell
10.0.1.21


14 4.991584 00:04:75:ac:88:a5 00:50:bf
:75:23:bb ARP 10.0.1.11 is at
00:04:75:ac:88:a5


Which destinations are not reachable? Explain

PC2 and PC4 are not reachable because they are not in the same subnet as PC1.


Include the saved output of the routing table. Explain the entries in the

routing table and
discuss the values of the fields for each entry.

PC1

Kernel IP routing table

Destination Gateway Genmask Flags MSS Window irtt Iface

10.0.1.0 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 0 0 0 eth0

127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo


If PC1
want
s

to send

packets
to

any destination that has subnet 10.0.1.0 and netmask
255.255.255.0

throu
gh interface eth0
, PC1 can
send

directly.


If PC1

want
s

to send packets to
any destination that has subnet 169.
254.0.0 and netmask
255.255.0.0 through interface eth0,

PC1 can
send

directly
.


127.0.0.0 is the loop back.


PC2

Kernel IP routing table

Destin
ation Gateway Genmask Flags MSS Window irtt Iface

10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1

127.0.0.0 0.0.0.0

255.0.0.0 U 0 0 0 lo


If PC
2

wants to send packets to

any destination that has subnet 10.0.1.0 and netmask
255.255.255.0

through interface eth0
, PC
2

can
send

directly.


If PC
2

wants to send packets to

any destination that has s
ubnet

10.0.1.0 and netmask
255.255.255.0

through interface eth
1,

PC
2

can
send

directly
.
.


127.0.0.0 is the loop back.


PC4

Kernel IP routing table

Destination Gateway Genmask Flags MSS Window irtt Iface

10.0.1.0 10.0.3.1

255.255.255.0 UG 0 0 0 eth0

10.0.2.0 10.0.3.1 255.255.255.0 UG 0 0 0 eth0

10.0.3.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

127.0.0.0 0.0.0.0 255.0.0.0 U

0 0 0 lo


If PC4

want to send packets to

destination that has subnet 10.0.1.0 and netmask 255.255.255.0
through interface eth0, PC4 can directs the packets to gateway 10.0.3.1
.


If PC4 want to send packets to destination that has subnet 10.
0.2.0 and netmask 255.255.255.0
through interface eth0, PC4 can directs the packets to gateway 10.0.3.1.


If PC4 want to send packets to destination that has subnet 10.0.3.0 and netmask 255.255.255.0
through interface eth0, PC4 can send

them

directly.


127
.0.0.0 is the loop back.



EX 2

c. Include the output from Step3 in your lab report.

Router1#show interfaces

FastEthernet0/0 is up, line protocol is up


Hardware is AmdFE, address is 000d.292c.e600 (bia 000d.292c.e600)


Internet address is 10.0.2.1/24


MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,


reliability 255/255, txload 1/255, rxload 1/255


Encapsulation ARPA, loopback not set


Keepalive set (10 sec)


Half
-
duplex, 10Mb/s, 100BaseTX/FX


ARP type: ARPA, ARP Timeout 04:00:00


Last input 01:16
:32, output 00:00:01, output hang never


Last clearing of "show interface" counters never


Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 943


Queueing strategy: fifo


Output queue :0/40 (size/max)


5 minute input rate 0 bits/sec,

0 packets/sec


5 minute output rate 0 bits/sec, 0 packets/sec


64923 packets input, 6298761 bytes


Received 1330 broadcasts, 0 runts, 0 giants, 0 throttles


339063 input errors, 0 CRC, 0 frame, 0 overrun, 339060 ignored


0 watchdog


0

input packets with dribble condition detected


445533 packets output, 29089576 bytes, 0 underruns


0 output errors, 2407 collisions, 0 interface resets


0 babbles, 0 late collision, 22 deferred


314509 lost carrier, 0 no carrier


0 out
put buffer failures, 0 output buffers swapped out

FastEthernet0/1 is up, line protocol is up


Hardware is AmdFE, address is 000d.292c.e601 (bia 000d.292c.e601)


Internet address is 10.0.3.1/24


MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,


reliabil
ity 255/255, txload 1/255, rxload 1/255


Encapsulation ARPA, loopback not set


Keepalive set (10 sec)


Half
-
duplex, 10Mb/s, 100BaseTX/FX


ARP type: ARPA, ARP Timeout 04:00:00


Last input 00:01:20, output 00:00:01, output hang never


Last clearing of
"show interface" counters never


Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 942


Queueing strategy: fifo


Output queue :0/40 (size/max)


5 minute input rate 0 bits/sec, 0 packets/sec


5 minute output rate 0 bits/sec, 0 packets
/sec


110829 packets input, 9485460 bytes


Received 952 broadcasts, 0 runts, 0 giants, 0 throttles


338401 input errors, 1 CRC, 1 frame, 0 overrun, 338400 ignored


0 watchdog


0 input packets with dribble condition detected


1471507

packets output, 90658352 bytes, 0 underruns


0 output errors, 2473 collisions, 0 interface resets


0 babbles, 0 late collision, 21 deferred


109301 lost carrier, 0 no carrier


0 output buffer failures, 0 output buffers swapped out


Router1
#show running
-
config

Building configuration...



Current configuration : 690 bytes

!

version 12.2

no service timestamps debug uptime

no service timestamps log uptime

no service password
-
encryption

!

hostname Router1

!

enable password rootroot

!

ip subnet
-
z
ero

!

!

no ip domain
-
lookup

!

!

!

!

interface FastEthernet0/0


ip address 10.0.2.1 255.255.255.0


no ip mroute
-
cache


duplex auto


speed auto


no cdp enable


bridge
-
group 1

!

interface FastEthernet0/1


ip address 10.0.3.1 255.255.255.0


no ip mroute
-
cache


duplex auto


speed auto


no cdp enable


bridge
-
group 1

!

ip classless

no ip http server

no ip pim bidir
-
enable

!

!

no cdp run

bridge 1 protocol ieee

bridge 1 priority 64

!

line con 0

line aux 0

line vty 0


password rootroot


login

line vty 1 4


login

!

!

end


d. Include the saved output of the routing table from Steps 1 and 2. Explain the fields of
the routing tables entries of the Cisco router. Explain how the routing table has changed
from step1 to step3.


From Step1

Router1#show ip route

Codes: C
-

conn
ected, S
-

static, I
-

IGRP, R
-

RIP, M
-

mobile, B
-

BGP


D
-

EIGRP, EX
-

EIGRP external, O
-

OSPF, IA
-

OSPF inter area


N1
-

OSPF NSSA external type 1, N2
-

OSPF NSSA external type 2


E1
-

OSPF external type 1, E2
-

OSPF external type
2, E
-

EGP


i
-

IS
-
IS, L1
-

IS
-
IS level
-
1, L2
-

IS
-
IS level
-
2, ia
-

IS
-
IS inter area


*
-

candidate default, U
-

per
-
user static route, o
-

ODR


P
-

periodic downloaded static route



Gateway of last resort is not set




10.0.0.0/24 i
s subnetted, 2 subnets

C 10.0.2.0 is directly connected, FastEthernet0/0

C 10.0.3.0 is directly connected, FastEthernet0/1

Explanation
:

router 1 is directly connected to 10.0.2.0 via interface
FastEthernet0/0
.



router 1 is directly connected
to 10.0.3.0 via interface
FastEthernet0/
1.

From Step2

Router1#show ip route

Codes: C
-

connected, S
-

static, I
-

IGRP, R
-

RIP, M
-

mobile, B
-

BGP


D
-

EIGRP, EX
-

EIGRP external, O
-

OSPF, IA
-

OSPF inter area


N1
-

OSPF NSSA external type 1
, N2
-

OSPF NSSA external type 2


E1
-

OSPF external type 1, E2
-

OSPF external type 2, E
-

EGP


i
-

IS
-
IS, L1
-

IS
-
IS level
-
1, L2
-

IS
-
IS level
-
2, ia
-

IS
-
IS inter area


*
-

candidate default, U
-

per
-
user static route, o
-

ODR


P
-

periodic downloaded static route



Gateway of last resort is not set



10.0.0.0/24 is subnetted, 3 subnets

C 10.0.2.0 is directly connected, FastEthernet0/0

C 10.0.3.0 is directly connected, FastEthernet0/1

S 10.0.1.0 [1/0] via 10.0
.2.22



Explanation
:

router 2 is directly connected to 10.0.2.0 via interface
FastEthernet0/0
.



router 2 is directly connected to 10.0.3.0 via interface
FastEthernet0/
1.



R
outer 2 will redirect any packets to 10.0.2.22 if the packets

s destination is



10.0.1.0.


How? enter this command:

ip route 10.0.1.0 255.255.255.0 10.0.2.22


Ex3

b. Use the ethereal output and the previously saved routing table to explain the operations
of traceroute.


traceroute is a TCP/IP utility which allows the user to determin
e the route packets take to reach a
particular host. traceroute works by increasing the "time to live" value of each successive packet
sent. The first packet has a TTL value of one, the second two, and so on. When a packet passes
through a host, the host d
ecrements the TTL value by one and forwards the packet to the next
host. When a packet with a TTL of one reaches a host, the host discards the packet and sends
an ICMP time exceeded (type 11) packet to the sender. The traceroute utility uses these returnin
g
packets to produce a list of hosts that the packets have traversed en route to the destination.


c. determine the source and destination addresses in the Ethernet and IP headers for the
ICMP echo request messages that were captured at PC1.

Source is 10.0
.1.11 (00:04:75:ad:01:72) and Destination is 10.0.3.41(00:04:75:ad:04:a9)


determine the source and destination addresses in the Ethernet and IP headers for the
ICMP echo request messages that were captured at PC4.

Source is 10.0.1.11 (00:04:75:ac:87:1b) a
nd Destination is 10.0.3.41(00:0a:b7:c1:eb:41)


Use your previous answers to explain how the source and destination Ethernet and IP
addresses are changed when a datagram is forwarded by a router.

The source and destination of IP addresses are not changed;
however, the source and
destination Ethernet are changed because from PC1 to PC4
,

we must go through a
n intermediate
device, which is the

router.

As we can see, the MAC destination address at PC1 is
00:04:75:ad:04:a9,
which corresponds to the eth0 interfac
e ip address of the router;
and the MAC
source address at PC4 is
00:04:75:ac:87:1b, which
corresponds to
the
eth1 interface of the router.


Ex3 d

The matches for 10.0.3.9 are:

10.0.3.9 10.0.1.81 255.255.255.255 UGH 0 0 0 eth0

10
.0.3.0 10.0.1.61 255.255.255.0 UG 0 0 0 eth0

10.0.3.0 10.0.1.21 255.255.255.0 UG 0 0 0 eth0

10.0.0.0 10.0.1.71 255.255.0.0 UG 0 0 0 eth0


The matches for 10.0.3.
14 are:

10.0.3.0 10.0.1.61 255.255.255.0 UG 0 0 0 eth0

10.0.3.0 10.0.1.21 255.255.255.0 UG 0 0 0 eth0

10.0.0.0 10.0.1.71 255.255.0.0 UG 0 0 0 eth0


The matches f
or 10.0.4.1 are:

10.0.0.0 10.0.1.71 255.255.0.0 UG 0 0 0 eth0


Explain how PC1 resolves multiple matches in the routing table.

PC1 will find the closest match for an ip address if there are multiple matches. For example, if

PC1 wants to send packets to destination 10.0.3.9,

we can see that the

ip address 10.0.3.9 is in
the routing table and of course is the closest match.

Other matches like 10.0.3.0 and 10.0.0.0 are
not as close as 10.0.3.9. Then if there are two closest mat
ches, PC1 will choose the first match,
and this is the case with 10.0.3.14, where PC1 directs packets to 10.0.1.61.


Relevant output data:

For 10.0.3.9:


1 0.000000 00:04:75:ac:88:a5 ff:ff:ff:ff:ff:ff ARP Who has 10.0.1.81? Tell 10.0
.1.11

For 10.0.3.14:


4 21.281227 00:04:75:ac:88:a5 ff:ff:ff:ff:ff:ff ARP Who has 10.0.1.61? Tell 10.0.1.1
1


PC1’s Routing table

Kernel IP routing table

Destination Gateway Genmask Flags MSS Window irtt Iface

10.
0.3.9 10.0.1.81 255.255.255.255 UGH 0 0 0 eth0

10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

10.0.2.0 10.0.1.21 255.255.255.0 UG 0 0 0 eth0

10.0.3.0 10.0.1.61

255.255.255.0 UG 0 0 0 eth0

10.0.3.0 10.0.1.21 255.255.255.0 UG 0 0 0 eth0

10.0.0.0 10.0.1.71 255.255.0.0 UG 0 0 0 eth0

169.254.0.0 0.0.0.0 255.255.0.0

U 0 0 0 eth0

127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo


3e

Output on PC1:


No. Time Source Destination Protocol Info


8 68.646836 00:50:bf:73:47:6a ff:ff:ff:ff
:ff:ff ARP Who has 10.0.1.21? Tell 10.0.1.11


9 68.647054 00:50:bf:74:fe:15 00:50:bf:73:47:6a ARP 10.0.1.21 is at
00:50:bf:74:fe:15


10 68.647077 10.0.1.11 10.0.10.110 ICMP Echo (ping) request



11 68.647508 10.0.1.21 10.0.1.11 ICMP Redirect


12 68.647555 00:50:bf:73:47:6a ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.11


13 68.647513 00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff A
RP Who has 10.0.10.110? Tell
10.0.1.21


14 69.639327 00:50:bf:73:47:6a ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.11


15 69.647302 00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
1
0.0.1.21


16 69.649473 10.0.1.11 10.0.10.110 ICMP Echo (ping) request


17 69.649779 10.0.1.21 10.0.1.11 ICMP Redirect


19 70.639327 00:50:bf:73:47:6a ff:ff:ff:ff:ff:ff ARP

Who has 10.0.10.110? Tell
10.0.1.11


20 70.647297 00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.21


21 70.649471 10.0.1.11 10.0.10.110 ICMP Echo (ping) request


22 70.6497
72 10.0.1.21 10.0.1.11 ICMP Redirect


23 71.647364 10.0.1.21 10.0.1.11 ICMP Destination unreachable


24 71.647523 10.0.1.21 10.0.1.11 ICMP Destination unreach
able


25 71.647598 10.0.1.21 10.0.1.11 ICMP Destination unreachable


26 71.652616 10.0.1.11 10.0.10.110 ICMP Echo (ping) request


27 71.652901 10.0.1.21 10.0.1.11

ICMP Redirect


28 71.652933 00:50:bf:73:47:6a ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.11


29 71.653066 00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.21


30 72.6473
00 00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.21


31 72.649334 00:50:bf:73:47:6a ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.11


32 72.651624 10.0.1.11 10.0.10.1
10 ICMP Echo (ping) request


33 72.651908 10.0.1.21 10.0.1.11 ICMP Redirect


34 73.647297 00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.21


35 73.649334 00
:50:bf:73:47:6a ff:ff:ff:ff:ff:ff ARP Who has 10.0.10.110? Tell
10.0.1.11


36 74.647365 10.0.1.21 10.0.1.11 ICMP Destination unreachable


37 74.647516 10.0.1.21 10.0.1.11 ICMP

Destination unreachable


38 79.647288 00:50:bf:74:fe:15 00:50:bf:73:47:6a ARP Who has 10.0.1.11? Tell
10.0.1.21


39 79.647313 00:50:bf:73:47:6a 00:50:bf:74:fe:15 ARP 10.0.1.11 is at
00:50:bf:73:47:6a



How far ICMP
Echo Request message travels?

ICMP Echo Request message travels as far as 10.0.1.21.


Which, if any, ICMP Echo Reply message returns to PC1?

From 10.0.1.21 to 10.0.1.11: ICMP Destination unreachable


EX 4

When PC4 pings PC1, it broadcasts ARP request,
when Proxy ARP sees it,

it’ll see if it can find
the requested address

from some other subnets
, if the requested address is found, it’ll talk to
PC4 that the requested MAC address is
at
its (the Proxy ARP
’s
) MAC address.

Basically, a Proxy ARP
responds to

the ARP requests on one interface as being responsible for
addresses of device addresses on another interface.
It

can then receive and forward packets
addressed to the other devices.



EX5


[root@PC2 root]# route

Kernel IP routing table

Destination Ga
teway Genmask Flags Metric Ref Use Iface

10.0.2.0 * 255.255.255.0 U 0 0 0 eth0

10.0.3.0 10.0.2.1 255.255.255.0 UG 0 0 0 eth0

127.0.0.0 * 255.0.0.0

U 0 0 0 lo

[root@PC2 root]# route
-
C

Kernel IP routing cache

Source Destination Gateway Flags Metric Ref Use Iface

PC2 PC2 PC2 l 0 0 3 lo

PC2 PC2

PC2 l 0 0 1 lo





Yes. There is a difference between contents of the routing table and the routing cache
after the ICMP route redirect message.



The cache was empty.



When the host sent the datagram to 10.0.3.0, router1

redirected the packet to 10.0.3.0
and told PC2 to update its routing table entry to send future datagrams to router2.


Router1#show ip route

Codes: C
-

connected, S
-

static, I
-

IGRP, R
-

RIP, M
-

mobile, B
-

BGP


D
-

EIGRP, EX
-

EIGRP external, O

-

OSPF, IA
-

OSPF inter area


N1
-

OSPF NSSA external type 1, N2
-

OSPF NSSA external type 2


E1
-

OSPF external type 1, E2
-

OSPF external type 2, E
-

EGP


i
-

IS
-
IS, L1
-

IS
-
IS level
-
1, L2
-

IS
-
IS level
-
2, *
-

candidate default


U
-

per
-
user static route, o
-

ODR


Gateway of last resort is not set



10.0.0.0/24 is subnetted, 3 subnets

C 10.0.2.0 is directly connected, Ethernet0/1

S 10.0.3.0 [1/0] via 10.0.2.2

C 10.0.1.0 is directly connected, Ethernet0/0

Rout
er1#show ip cache

IP routing cache 0 entries, 0 bytes


0 adds, 0 invalidates, 0 refcounts

Minimum invalidation interval 2 seconds, maximum interval 5 seconds,


quiet interval 3 seconds, threshold 0 requests

Invalidation rate 0 in last second, 0 in last

3 seconds

Last full cache invalidation occurred 00:18:12 ago


Prefix/Length Age Interface Next Hop


Router2#show ip route

Codes: C
-

connected, S
-

static, I
-

IGRP, R
-

RIP, M
-

mobile, B
-

BGP


D
-

EIGRP, EX
-

EIGRP external,
O
-

OSPF, IA
-

OSPF inter area


N1
-

OSPF NSSA external type 1, N2
-

OSPF NSSA external type 2


E1
-

OSPF external type 1, E2
-

OSPF external type 2, E
-

EGP


i
-

IS
-
IS, L1
-

IS
-
IS level
-
1, L2
-

IS
-
IS level
-
2, *
-

candidate

default



U
-

per
-
user static route, o
-

ODR


Gateway of last resort is not set



10.0.0.0/24 is subnetted, 2 subnets

C 10.0.2.0 is directly connected, Ethernet0/1

C 10.0.3.0 is directly connected, Ethernet0/0

Router2#show ip cache

IP routing cache
0 entries, 0 bytes


0 adds, 0 invalidates, 0 refcounts

Minimum invalidation interval 2 seconds, maximum interval 5 seconds,


quiet interval 3 seconds, threshold 0 requests

Invalidation rate 0 in last second, 0 in last 3 seconds

Last full cache invalida
tion occurred 00:00:26 ago


Prefix/Length Age Interface Next Hop




Router1 redirects the packets sent to 10.0.3.10 and tells PC2 to update its routing table
entries and forward future datagrams to 10.0.2.2.



EX6

Are the two ICMP pack
ets that you saved identical? If not, what is different? Include the
packet data in your lab report to substantiate your claims.

Yes, they are identical


6 22.453151 10.0.4.10 10.0.1.10 ICMP Echo (ping) request


7 2
2.454025 10.0.4.10 10.0.1.10 ICMP Echo (ping) request


Why does the ICMP Echo Request packet not loop forever in the network?

Because there is a field in ip packet’ header, Time to live (TTL), that indicates how many more
hops

this packet should be allowed to make before being discarded or returned. See the
following:

28 22.466175 10.0.4.4 10.0.4.10 ICMP Time
-
to
-
live exceeded


EX 7

Explain what you observed in steps3, 4, and 5…

I find routing tabl
es and arp caches of the involved PCs are updated each time a ping is issued.


If PC3 had no default entry in its table, would you have seen the same results? Explain…


From PC3 to PC
2
:

Pc3:

10.0.2.137
-
>

00001010 00000000 00000010 10001001


Net mask
-
>

11111111 11111111 11111111 11111000




00001010 00000000 00000010 10001
000


Pc2
:

10.0.2.137
-
>

00001010 00000000 00000010 00001010


Net mask
-
>

11111111 11111111 11111111 11111000




00001010 00000000 00
000010 00001
000


Since

00001010 00000000 00000010 10001
000”

is not

00001010 00000000 00000010
00001
000” so pc3 cannot reach pc2, however, on the other hand,


From PC2 to PC3:


Pc2:

10.0.2.10
-
>

00001010 00000000 00000010 00001010


Net mask
-
>

11111111 1
1111111 11111111 00000000




00001010 00000000 00000010 00000000


Pc3:

10.0.2.137
-
>

00001010 00000000 00000010 10001001


Net mask
-
>

11111111 11111111 11111111 00000000




00001010 00000000 00000010 00000000


Since they both ha
ve “00001010 00000000 00000010 00000000” so they are in the same subnet,
and hence, PC2 can reach PC3.


From PC3 to PC4:

Pc3:

10.0.2.137
-
>

00001010 00000000 00000010 10001001


Net mask
-
>

11111111 11111111 11111111 11111000




00001010 00000000 00000010 10001000


Pc
4
:

10.0.2.137
-
>

00001010 00000000 00000010
1
000101
1


Net mask
-
>

11111111 11111111 11111111 11111000




00001010 00000000 00000010 10001
000


Since they both have “00001010 00000000 00000010

10001000” so they are in

the same subnet,
and hence, PC3

can reach PC
4
.


From PC4 to PC3:

Pc
4
:

10.0.2.10
-
>

00001010 00000000 00000010 10001011


Net mask
-
>

11111111 11111111 11111111 00000000




00001010 00000000 00000010 00000000


Pc3:

10.0.2.137
-
>

00001010 00000000 00000010 10001001


Net mask
-
>

11111111 11111111 11111111 00000000




00001010 00000000 00000010 00000000


Since they both have “00001010 00000000 00000010 00000000” so they are in the same subnet,
and hence, PC
4

can reach PC
3
.