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 same 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 packets 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 10.0.1.11
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 4.023097 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
00
0 eth0
169.254.0.0 0.0.0.0
255.255.0.0 U
00
0 eth0
127.0.0.0
0.0.0.0
255.0.0.0
U
00
0 lo
If PC1 wants to send packets to any destination that has subnet 10.0.1.0 and netmask
255.255.255.0 through interface eth0, PC1 can send directly.
If PC1 wants 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
Destination Gateway
10.0.1.0
0.0.0.0
10.0.1.0
0.0.0.0
127.0.0.0
0.0.0.0
Genmask
Flags MSS Window irtt Iface
255.255.255.0 U
00
0 eth0
255.255.255.0 U
00
0 eth1
255.0.0.0
U
00
0 lo
If PC2 wants to send packets to any destination that has subnet 10.0.1.0 and netmask
255.255.255.0 through interface eth0, PC2 can send directly.
If PC2 wants to send packets to any destination that has subnet 10.0.1.0 and netmask
255.255.255.0 through interface eth1, PC2 can send directly..
127.0.0.0 is the loop back.
PC4
Kernel IP routing table
Destination Gateway
10.0.1.0
10.0.3.1
10.0.2.0
10.0.3.1
Genmask
Flags MSS Window irtt Iface
255.255.255.0 UG
00
0 eth0
255.255.255.0 UG
00
0 eth0
10.0.3.0
127.0.0.0
0.0.0.0
0.0.0.0
255.255.255.0 U
255.0.0.0
U
00
00
0 eth0
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 output 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,
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 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-zero
!
!
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 - 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, 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
C
C
S
10.0.0.0/24 is subnetted, 3 subnets
10.0.2.0 is directly connected, FastEthernet0/0
10.0.3.0 is directly connected, FastEthernet0/1
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.
Router 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 determine 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 decrements 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 returning
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) and 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 an 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 interface 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
00
10.0.3.0
10.0.1.61
255.255.255.0 UG
00
10.0.3.0
10.0.1.21
255.255.255.0 UG
00
10.0.0.0
10.0.1.71
255.255.0.0 UG
00
0 eth0
0 eth0
0 eth0
0 eth0
The matches for 10.0.3.14 are:
10.0.3.0
10.0.1.61
255.255.255.0 UG
10.0.3.0
10.0.1.21
255.255.255.0 UG
10.0.0.0
10.0.1.71
255.255.0.0 UG
00
00
00
0 eth0
0 eth0
0 eth0
The matches for 10.0.4.1 are:
10.0.0.0
10.0.1.71
255.255.0.0
00
0 eth0
UG
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 matches, 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
For 10.0.3.14:
4 21.281227 00:04:75:ac:88:a5
PC1’s Routing table
Kernel IP routing table
Destination Gateway
10.0.3.9
10.0.1.81
10.0.1.0
0.0.0.0
10.0.2.0
10.0.1.21
10.0.3.0
10.0.1.61
10.0.3.0
10.0.1.21
10.0.0.0
10.0.1.71
169.254.0.0 0.0.0.0
127.0.0.0
0.0.0.0
ff:ff:ff:ff:ff:ff
ARP
Who has 10.0.1.81? Tell 10.0.1.11
ff:ff:ff:ff:ff:ff
ARP
Who has 10.0.1.61? Tell 10.0.1.11
Genmask
Flags MSS Window irtt Iface
255.255.255.255 UGH
00
0 eth0
255.255.255.0 U
00
0 eth0
255.255.255.0 UG
00
0 eth0
255.255.255.0 UG
00
0 eth0
255.255.255.0 UG
00
0 eth0
255.255.0.0 UG
00
0 eth0
255.255.0.0 U
00
0 eth0
255.0.0.0
U
00
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 ARP
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
10.0.1.21
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 70.649772 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 unreachable
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 72.647300 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
10.0.1.11
32 72.651624
33 72.651908
34 73.647297
10.0.1.21
35 73.649334
10.0.1.11
36 74.647365
37 74.647516
38 79.647288
10.0.1.21
39 79.647313
00:50:bf:73:47:6a
00:50:bf:73:47:6a
ff:ff:ff:ff:ff:ff
ARP
Who has 10.0.10.110? Tell
10.0.1.11
10.0.10.110
10.0.1.21
10.0.1.11
00:50:bf:74:fe:15 ff:ff:ff:ff:ff:ff
ICMP Echo (ping) request
ICMP Redirect
ARP
Who has 10.0.10.110? Tell
00:50:bf:73:47:6a
ARP
ff:ff:ff:ff:ff:ff
Who has 10.0.10.110? Tell
10.0.1.21
10.0.1.11
ICMP Destination unreachable
10.0.1.21
10.0.1.11
ICMP Destination unreachable
00:50:bf:74:fe:15 00:50:bf:73:47:6a ARP
Who has 10.0.1.11? Tell
00:50:bf:73:47:6a
00:50:bf:74:fe:15
ARP
10.0.1.11 is at
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 Gateway
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
Router1#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 invalidation 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 packets 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 22.454025 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 tables 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 PC2:
Pc3:
10.0.2.137 ->
Net mask ->
Pc2:
10.0.2.137 ->
Net mask ->
00001010 00000000 00000010 10001001
11111111 11111111 11111111 11111000
00001010 00000000 00000010 10001000
00001010 00000000 00000010 00001010
11111111 11111111 11111111 11111000
00001010 00000000 00000010 00001000
Since “00001010 00000000 00000010 10001000” is not “00001010 00000000 00000010
00001000” so pc3 cannot reach pc2, however, on the other hand,
From PC2 to PC3:
Pc2:
10.0.2.10 ->
Net mask ->
00001010 00000000 00000010 00001010
11111111 11111111 11111111 00000000
00001010 00000000 00000010 00000000
Pc3:
10.0.2.137 ->
Net mask ->
00001010 00000000 00000010 10001001
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, PC2 can reach PC3.
From PC3 to PC4:
Pc3:
10.0.2.137 ->
Net mask ->
Pc4:
10.0.2.137 ->
Net mask ->
00001010 00000000 00000010 10001001
11111111 11111111 11111111 11111000
00001010 00000000 00000010 10001000
00001010 00000000 00000010 10001011
11111111 11111111 11111111 11111000
00001010 00000000 00000010 10001000
Since they both have “00001010 00000000 00000010 10001000” so they are in the same subnet,
and hence, PC3 can reach PC4.
From PC4 to PC3:
Pc4:
10.0.2.10 ->
Net mask ->
Pc3:
10.0.2.137 ->
Net mask ->
00001010 00000000 00000010 10001011
11111111 11111111 11111111 00000000
00001010 00000000 00000010 00000000
00001010 00000000 00000010 10001001
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, PC4 can reach PC3.