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IP Training Programme
Module 1: IP Generic
Session 3: IP Services
Subjects
• Review
• The IP Address continued…
• Routing protocols (Concept)
• Firewalll and NAT
• DNS server and DNS operation concept
• DHCP server including options
• Network security in general
SMALL REVIEW FROM
SESSION 1 AND 2
Just the important stuff
IP Classes
Class Purpose First byte between Subnet mask Prefix Max hosts
A Unicast 0 and 127 255.0.0.0 /8 16.777.214
B Unicast 128 and 191 255.255.0.0 /16 65.534
C Unicast 192 and 223 255.255.255.0 /24 254
Class Purpose First byte between Subnet mask Prefix Max hosts
D Multicast 224 and 239 None special None -
E Reserved 239 and 255 None None -
Additional classes
Between logical net
61.14
WAN link
Net: 194.182.53/24
10 11 12 13
1
Net: 182.114/16
61.13
1.1
67.19 112.4
Router
Router
TCP/IP vs. ISO
• TCP/IP was developed with four layers.
TCP in IP in Ethernet
Type
Contains the value 800 showing
the Ethernet frame contains an
IP packet
Destination
MAC address
6 Byte
Source
MAC Address
6 Byte 2 Byte
IP packetFrame Check
(Checksum CRC)
Source
IP Address
32 bit
Destination
IP Address
32 bit
IP packet
(Simplified)
Ethernet frame
Containing IP Packet
Ethernet data
46 Byte to 1500 Bytes
Data in IP packet. Variable size
TCP PacketProtocol
Contains the value 6 indicating
the IP packet contains a TCP
packet
Sequence
number
Data in TCP packet. Variable sizeTCP packet
(Simplified)
Destination
Port
Source
port
Session layer related information
TCP Data
Session layer part of TCP
(Simplified)
TCP and UDP
• TCP builds virtual connections between end points. (hosts) • Connection oriented protocol – Create, maintain and close• Reliable transport.• The transmitter splits data segments. (Ethernet maximum 1500 bytes data)• The receiver assemble the data segments.• The receiver acknowledges the reception of segments. Lost segments are
retransmitted.
• UDP transports data between end points. (hosts)• Connection less. Just send data and hoping the receiver is on-line. • Unreliable transport. (No guarantee the data is delivered)• The receiver do not assemble the data segments.• No flow control• No error control or recovery
Internet
Client
Local
DNS server
. root
DNS server
.no
DNS server
ascom.no
DNS Server
www.ascom.no
Web server
1
2
3
4
5
6
6: Get the web-page
The local DNS server will normally be a caching DNS server
meaning it will remember what it learns reducing traffic and decreasing
respond time. All information has a time-to-live. The information will be
deleted when time-to-live expires.
THE IP ADDRESS CONTINUED
Beyond the original IP classess A, B and C
Classfull IP addresses
• The original classfull divided the unicast
space in three fixed classes
– IP address shortage because of internet
growth as early as 1993
Class First byte between Subnet mask Prefix Max hosts Networks
A 0 and 127 255.0.0.0 /8 16.777.214 128
B 128 and 191 255.255.0.0 /16 65.534 16.384
C 192 and 223 255.255.255.0 /24 254 2.097.152
Prefix Subnet mask - decimal Subnet mask - binary
/8 255.0.0.0 11111111.00000000.00000000.00000000
/16 255.255.0.0 11111111.11111111.00000000.00000000
/24 255.255.255.0 11111111.11111111.11111111.00000000
Network and broadcast
• Two IP addresses of each logical network is
reserved for special purposes. They are
illegal as host IP addresses
– All host bits “0” is the logical network name
– All host bits “1” is the local broadcast IP address
• For example the 192.168.,100.0/24 network
– 192.168.100.0 is the network name
– 192.168.100.255 is the broadcast address
– Usable IP address ranges from
• 192.168.100.1 to 192.168.100.254
• A total of 254 usable addresses
Boson subnet calculator
Subnetting
• Classfull IP addresses
• For example: 172.16.4.5/16
– Network part 172.16
– Host part: 4.5
• Classless IP addresses
• For example 172.16.4.5/24
– Network part: 172.16.4
– Host part: 5
Network part Host part
Network part Subnet part Host part
Classless IP addresses
• Subnettet class B network as /24
– One class B net subnettet to 256 subnets
Network Subnet mask Max hosts
172.16.0.0 255.255.255.0 254
172.16.1.0 255.255.255.0 254
172.16.2.0 255.255.255.0 254
... ... ...
172.16.253.0 255.255.255.0 254
172.16.254.0 255.255.255.0 254
172.16.255.0 255.255.255.0 254
Exponentiation
• Mathematical operation
• Called “potens” in Swedish, Norwegian and
Danish.
• 25 = 2 ^ 5 = 2 * 2 * 2 * 2 * 2 = 32
• 72 = 7 ^ 2 = 7 * 7 = 49
• 264 = 2 ^ 64 = 18.446.744.073.709.551.616
• Often used when dealing with numeric
systems.
Numeric systems II
83677*10^0 = 7*1 = 7
6*10^1 = 6*10 = 60
3*10^2 = 3*100 = 300
8*10^3 = 8*1000 = 8000
Decimal sum = 8367
10
11011*2^0 = 1*1 = 1
0*2^1 = 0*2 = 0
1*2^2 = 1*4 = 4
1*2^3 = 1*8 = 8
Decimal sum = 13
2
The binary byte
111111111*2^0 = 1*1 = 1
1*2^1 = 1*2 = 2
1*2^2 = 1*4 = 4
1*2^3 = 1*8 = 8
Decimal sum = 255
2
1*2^4 = 1*16 = 16
1*2^5 = 1*32 = 32
1*2^6 = 1*64 = 64
1*2^7 = 1*128 = 128
The binary byte
111110000*2^0 = 1*1 = 0
0*2^1 = 1*2 = 0
0*2^2 = 1*4 = 0
1*2^3 = 1*8 = 8
Decimal sum = 248
2
1*2^4 = 1*16 = 16
1*2^5 = 1*32 = 32
1*2^6 = 1*64 = 64
1*2^7 = 1*128 = 128
Classless IP addresses
• To adapt the size of a logical network to
customer networks the classes were
abandoned.
– Subnets is logical networks
prefix Subnet mask Subnets Max hosts
/24 255.255.255.0 1 254
/25 255.255.255.128 2 126
/26 255.255.255.192 4 62
/27 255.255.255.224 8 30
/28 255.255.255.240 16 14
/29 255.255.255.248 32 6
/30 255.255.255.252 64 2
Classless IP addresses
• A binary “1” in the subnet mask means the bit
belongs to the logical network or subnet
• A binary “0” in the subnet mask means the bit
belongs to the host part of the IP address
Prefix Subnet mask - decimal Subnet mask - binary
/24 255.255.255.0 11111111.11111111.11111111.00000000
/25 255.255.255.128 11111111.11111111.11111111.10000000
/26 255.255.255.192 11111111.11111111.11111111.11000000
/27 255.255.255.224 11111111.11111111.11111111.11100000
/28 255.255.255.240 11111111.11111111.11111111.11110000
/29 255.255.255.248 11111111.11111111.11111111.11111000
/30 255.255.255.252 11111111.11111111.11111111.11111100
ROUTING PROTOCOLS
The route table
• The route table is
– used by all hosts – including Routers.
– a list of all logical networks known by the host.
– Used to decide in which direction packets
should be send.
• The route table contains
– Destination network
– Direction
– Distance
The road sign
• Destination, Direction and Distance
Routertable R1
NETWORK SEND TO
195.181.54/24 195.181.54.0
195.181.55/24 192.168.1.10
195.181.56/24 192.168.1.6
0.0.0.0 192.168.1.6
Routertable R2
NETWORK SEND TO
195.181.54/24 192.168.1.9
195.181.55/24 195.181.55.0
195.181.56/24 192.168.1.14
0.0.0.0 192.168.1.14
Routertable R3
NETWORK SEND TO
195.181.54/24 192.168.1.5
195.181.55/24 192.168.1.13
195.181.56/24 195.181.56.0
0.0.0.0 195.181.56.1
Routertable R4
NETWORK SEND TO
195.181.54/24 195.181.56.2
195.181.55/24 195.181.56.2
195.181.56/24 195.181.56.0
0.0.0.0 192.168.1.17
Route tables on routers
I am on the 195.181.54.0/24 network
The destination network for the ping
packets is 195.181.56.0/24
I will send the pakets to my default gateway
Routertable R1
NETWORK SEND TO
195.181.54/24 195.181.54.0
195.181.55/24 192.168.1.10
195.181.56/24 192.168.1.6
0.0.0.0 192.168.1.6
Routertable R2
NETWORK SEND TO
195.181.54/24 192.168.1.9
195.181.55/24 195.181.55.0
195.181.56/24 192.168.1.14
0.0.0.0 192.168.1.14
Routertable R3
NETWORK SEND TO
195.181.54/24 192.168.1.5
195.181.55/24 192.168.1.13
195.181.56/24 195.181.56.0
0.0.0.0 195.181.56.1
Routertable R4
NETWORK SEND TO
195.181.54/24 195.181.56.2
195.181.55/24 195.181.56.2
195.181.56/24 195.181.56.0
0.0.0.0 192.168.1.17
Route tables on routers
I received a packet for 195.181.56.103
My routetable has an entry that says traffic to
195.181.56.0/24 should be sent to 192.168.1.6
Routertable R1
NETWORK SEND TO
195.181.54/24 195.181.54.0
195.181.55/24 192.168.1.10
195.181.56/24 192.168.1.6
0.0.0.0 192.168.1.6
Routertable R2
NETWORK SEND TO
195.181.54/24 192.168.1.9
195.181.55/24 195.181.55.0
195.181.56/24 192.168.1.14
0.0.0.0 192.168.1.14
Routertable R3
NETWORK SEND TO
195.181.54/24 192.168.1.5
195.181.55/24 192.168.1.13
195.181.56/24 195.181.56.0
0.0.0.0 195.181.56.1
Routertable R4
NETWORK SEND TO
195.181.54/24 195.181.56.2
195.181.55/24 195.181.56.2
195.181.56/24 195.181.56.0
0.0.0.0 192.168.1.17
Route tables on routers
I received a packet for 195.181.56.103
My routetable has an entry that says traffic to
195.181.56.0/24 should be sent to the
connected 195.181.56.0/24 network
Routertable R1
NETWORK SEND TO
195.181.54/24 195.181.54.0
195.181.55/24 192.168.1.10
195.181.56/24 192.168.1.6
0.0.0.0 192.168.1.6
Routertable R2
NETWORK SEND TO
195.181.54/24 192.168.1.9
195.181.55/24 195.181.55.0
195.181.56/24 192.168.1.14
0.0.0.0 192.168.1.14
Routertable R3
NETWORK SEND TO
195.181.54/24 192.168.1.5
195.181.55/24 192.168.1.13
195.181.56/24 195.181.56.0
0.0.0.0 195.181.56.1
Routertable R4
NETWORK SEND TO
195.181.54/24 195.181.56.2
195.181.55/24 195.181.56.2
195.181.56/24 195.181.56.0
0.0.0.0 192.168.1.17
Route tables on routers
I received a ping packet from 195.181.54.101
I will respond with a “pong” packet.
195.181.54.101 is on another logical network
so I will send the packet to my default gateway
Route table creation
• The route table in routers can be created
and maintained in two ways
1: Static route table entry
• Entries are entered manually
2: Dynamic route table entry
• Entries are sent between routers automatically
• Require the use of a Routing protocol – such as
– RIP, OSPF, IS-IS or BGP
Static vs. dynamic
• Static routes
– Routes entered manually by administrators
– Routes changed manually by administrators
– Time consuming and error prone
• Dynamic routes
– Routes automatically entered by a routing
protocol.
– Routes automatically changed by a routing
protocol.
Routing protocols
• A Routing Protocol is a protocol that
exchanges routing information between
routers.
• A router receives routing information from
other routers and learn their logical
networks.
• Popular routing protocols
– RIP, OSPF, BGP,EIGRP,IS-IS
RIP
• RIP – Routing Information Protocol – is a
popular routing protocol.
– Measures distance in HOP’s
– HOP’s is equal to numbers of routers on the
way to the distant logical network.
• RIP is a Distance Vector Routing protocol
– Distance = Number of HOP’s to destination
network
– Vector = Direction of destination network.
(Which neighbor to send packets to)
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
R1, R2 and R3 just booted
R4 swithced off
Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
Route table R3
NETWORK
NETWORK
SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
X
When a Router is booted – it will know only the IP
addresses and subnet masks of the logical networks
connected to its physical ports.
It will also know it is using the routing protocol RIP.
It has been configured by a technician.
RIP
• RIP will transmit its Routing table to its
neighbor routers every 30. seconds.
• The neighbors will learn the transmitting
routers logical networks.
• The neighbors will transmit their routing
tables so the local router learns their
logical networks.
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
R1 updates R2Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
192.168.1.8/30 192.168.1.9 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
R1
X
R2 receives a copy of R1
route table and insert it into its
own routing table
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
Two 192.168.1.8/30?Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
192.168.1.8/30 192.168.1.9 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
R1
X
A logical network can only
have one entry in the routing
table. 192.168.1.8/30 is
represented twice. One with a
HOP count of 1 and one with
a HOP count of 2
A logical network can only
have one entry in the routing
table. 192.168.1.8/30 is
represented twice. One with a
HOP count of 1 and one with
a HOP count of 2
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
Shortest HOP count chosenRoute table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
R1
X
The best route to a destination
network is the route with the
lowest number of HOP’s
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
R1 updates R3Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
R
1
X
R1 also updates the neighbor
R3. R3 learns R1’s network.
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
R2 updates R3Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
195.181.55/24 192.168.1.13 2X
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.6 2
All routers updatetRoute table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
195.181.55/24 192.168.1.13 2X
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.6 2
R4 the Default Gateway
switchet on
Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
195.181.55/24 192.168.1.13 2
Route table R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
0.0.0.0 192.168.1.17 2
R4 is a little special as it is
holds the Default Route to the
internet. It is statically
configured by a technician in
this case.
Route table R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.6 2
192.168.1.16/30 192.168.1.6 3
0.0.0.0 192.168.1.6 4
Convergence!
Everybody knows everybody
Route table R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
192.168.1.16/30 192.168.1.14 3
0.0.0.0 192.168.1.14 4
Route table R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
195.181.55/24 192.168.1.13 2
192.168.1.16/30 195.181.56.1 2
0.0.0.0 195.181.56.1 3
Route table R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
192.168.1.4/30 195.181.56.2 2
192.168.1.12/30 195.181.56.2 2
195.181.54/24 195.181.56.2 3
195.181.55/24 195.181.56.2 3
192.168.1.8/30 195.181.56.2 3
0.0.0.0 192.168.1.17 2
R3 updates R4.
R4 updates R3 which updates
R1 and R2
RIP - Technically
• Maximum HOP-Count = 15
–Network diameter should be below 15 routers
• HOP-Count = 16 means network unreachable
• RIP exist in two versions
–Version 1
• Uses broadcast and only allow classfull IP networks
–Version 2
• Uses multicast and allows classless IP networks
Route tabel R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.6 2
192.168.1.16/30 192.168.1.6 3
0.0.0.0 192.168.1.6 4
When changes occursRoute tabel R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
192.168.1.16/30 192.168.1.14 3
0.0.0.0 192.168.1.14 4
Route tabel R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
195.181.55/24 192.168.1.13 2
192.168.1.16/30 195.181.56.1 2
0.0.0.0 195.181.56.1 3
Route tabel R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
192.168.1.4/30 195.181.56.2 2
192.168.1.12/30 195.181.56.2 2
195.181.54/24 195.181.56.2 3
195.181.55/24 195.181.56.2 3
192.168.1.8/30 195.181.56.2 3
0.0.0.0 192.168.1.17 2
X
WAN line
Down
Route tabel R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.6 16
192.168.1.16/30 192.168.1.6 16
0.0.0.0 192.168.1.6 16
R1 and R3 detect change
Neighbor unreachable
Route tabel R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
192.168.1.16/30 192.168.1.14 3
0.0.0.0 192.168.1.14 4
Route tabel R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 16
192.168.1.8/30 192.168.1.5 16
195.181.55/24 192.168.1.13 2
192.168.1.16/30 195.181.56.1 2
0.0.0.0 195.181.56.1 3
Route tabel R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
192.168.1.4/30 195.181.56.2 2
192.168.1.12/30 195.181.56.2 2
195.181.54/24 195.181.56.2 3
195.181.55/24 195.181.56.2 3
192.168.1.8/30 195.181.56.2 3
0.0.0.0 192.168.1.17 2
X
Route tabel R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.10 3
192.168.1.16/30 192.168.1.10 4
0.0.0.0 192.168.1.10 5
New routes installed
in route table
Route tabel R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
192.168.1.16/30 192.168.1.14 3
0.0.0.0 192.168.1.14 4
Route tabel R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.13 3
192.168.1.8/30 192.168.1.13 2
195.181.55/24 192.168.1.13 2
192.168.1.16/30 195.181.56.1 2
0.0.0.0 195.181.56.1 3
Route tabel R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
192.168.1.4/30 195.181.56.2 2
192.168.1.12/30 195.181.56.2 2
195.181.54/24 195.181.56.2 3
195.181.55/24 195.181.56.2 3
192.168.1.8/30 195.181.56.2 3
0.0.0.0 192.168.1.17 2
X
Route tabel R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.10 3
192.168.1.16/30 192.168.1.10 4
0.0.0.0 192.168.1.10 5
What happens when
WAN works again?
Route tabel R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
192.168.1.16/30 192.168.1.14 3
0.0.0.0 192.168.1.14 4
Route tabel R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.13 3
192.168.1.8/30 192.168.1.13 2
195.181.55/24 192.168.1.13 2
192.168.1.16/30 195.181.56.1 2
0.0.0.0 195.181.56.1 3
Route tabel R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
192.168.1.4/30 195.181.56.2 2
192.168.1.12/30 195.181.56.2 2
195.181.54/24 195.181.56.2 3
195.181.55/24 195.181.56.2 3
192.168.1.8/30 195.181.56.2 3
0.0.0.0 192.168.1.17 2
X
Route tabel R1
NETWORK SEND TO HOP
195.181.54/24 195.181.54.1 1
192.168.1.4/30 192.168.1.5 1
192.168.1.8/30 192.168.1.9 1
195.181.55/24 192.168.1.10 2
192.168.1.12/30 192.168.1.10 2
195.181.56/24 192.168.1.6 2
192.168.1.16/30 192.168.1.6 3
0.0.0.0 192.168.1.6 4
It returns to shortest
HOP count at the next
updates among the routers
Route tabel R2
NETWORK SEND TO HOP
195.181.55/24 195.181.55.1 1
192.168.1.8/30 192.168.1.10 1
192.168.1.12/30 192.168.1.13 1
195.181.54/24 192.168.1.9 2
192.168.1.4/30 192.168.1.9 2
195.181.56/30 192.168.1.14 2
192.168.1.16/30 192.168.1.14 3
0.0.0.0 192.168.1.14 4
Route tabel R3
NETWORK SEND TO HOP
195.181.56/24 195.181.56.2 1
192.168.1.4/30 192.168.1.6 1
192.168.1.12/30 192.168.1.14 1
195.181.54/24 192.168.1.5 2
192.168.1.8/30 192.168.1.5 2
195.181.55/24 192.168.1.13 2
192.168.1.16/30 195.181.56.1 2
0.0.0.0 195.181.56.1 3
Route tabel R4
NETWORK SEND TO HOP
195.181.56/30 195.181.56.1 1
192.168.1.16/30 192.168.1.18 1
192.168.1.4/30 195.181.56.2 2
192.168.1.12/30 195.181.56.2 2
195.181.54/24 195.181.56.2 3
195.181.55/24 195.181.56.2 3
192.168.1.8/30 195.181.56.2 3
0.0.0.0 192.168.1.17 2
Routing protocols
• Routing protocols keep the routing tables
up-to-date in the routers.
• Routing protocols like RIP are used in
small companies.
• OSPF and EIGRP are used in enterprises.
• The Internet uses BGP as a worldwide
routing protocols keeping track of 300.000
to 400.000 routes.
DI-614+
Wireless
Broadband
Router
LINK/ACT
Speed 10/100M4321WLANWAN
M1
M2
PowerD-Link
Firewalls and NAT
NAT: Network Address Translation
ADSL physical
Internettet
ADSL
Modem
Bolig
DI-614+Wireless
Broadband
Router
LINK/ACT
Speed 10/100M4321WLANWAN
M1
M2
PowerD-Link
ADSL logical
Home
Internet
provider
Home
ADSL Router
with NAT
19
2.1
68
.0.0
/24
1
101
102
103
9
10
Home
Home
80.1
.9.1
2/3
0
BBRAS
80.1.9.8/30
22
14
13
80.1
.9.1
6/30
18
17
21
80.1.9.20/30
Small home Router
Internet
provider
Home
19
2.1
68
.0.0
/24
1
101
102
103
9
10
BBRAS
80.1.9.8/30
SOHO Router
OutsideInside
DHCP
Client
DHCP
Server
Internet provider
DHCP Server
F
I
R
E
W
A
L
L
and
N
A
TDHCP
Clients
NAT translation
private IP addresses
• NAT: Network Address Translation
-one to one IP address translation
• Translates IP addresses from inside to outside network
• Private IP adresses allocated to be used behind NAT
-10.0.0.0/8
- 10.0.0.0 to 10.255.255.255
-172.16.0.0/12
- 172.16.0.0 to 172.31.255.255
-192.168.0.0/16
- 192.168.0.0 to 192.168.255.255
• NAT hides the inside network (LAN) from the outside
NAT table on the router
Internet
SOHO Router
with NAT
Inside net: 192.168.0.0/24
From
Protocol
To
From
To
Inside network NAT table Outside networkProtocol
NAT tabel
101 102 103
1WAN address
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
Dynamic NAT table
Internet
SOHO Router
with NAT
Inside net: 192.168.0.0/24
From
192.168.0.101
Protocol
TCP
To
80.80.12.116
From
To
NAT tabelProtocol
NAT tabel
101 102 103
1WAN address
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
From IP
192.168.0.101Data TCP
to IP
80.80.12.116
Inside network NAT table Outside network
NAT table
From inside to outside IP address
InternetSOHO Router
With NAT
Inside net: 192.168.0.0/24
From
192.168.0.101
Protocol
TCP
To
80.80.12.116
From
81.1.30.9
To
80.80.12.116
NAT tabelProtocol
TCP
NAT tabel
101 102 103
1
WAN address
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
From IP
192.168.0.101Data TCP
To IP
80.80.12.116
From IP
81.1.30.9Data TCP
To IP
80.80.12.116
Indre YdreInside network NAT table Outside network
NAT table – Return packets
InternetSOHO Router
with NAT
Inside net: 192.168.0.0/24
From
192.168.0.101
Protocol
TCP
To
80.80.12.116
From
81.1.30.9
To
80.80.12.116
NAT tabelProtocol
TCP
NAT tabel
101 102 103
1
WAN adsress
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
Data TCPTo IP
192.168.0.101Data TCP
To IP
81.1.30.9
Indre Ydre
From IP
80.80.12.116From IP
80.80.12.116
Inside network NAT table Outside network
NAT and PAT
• TCP and UDP uses port numbers.
• NAT/PAT software keeps track on connections using:
- Protocol ( eg. TCP)
- Inside from IP ( eg. 192.168.0.101)
- Inside from port ( eg. Port 1152)
- Out side to IP ( eg. 80.80.12.116)
- Out side to port ( eg. port 80)
• The five parameters describe a unique connection
NAT and PAT
InternetSOHO Router
with NAT and PAT
Inside net: 192.168.0.0/24
From
192.168.0.101:1152
Protocol
TCP
To
80.80.12.116:80
From
81.1.30.9:1152
To
80.80.12.116:80
NAT tabelProtocol
TCP
NAT tabel
101 102 103
1
WAN address
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
DataT
C
P
To IP
80.80.12.116
Indre Ydre
From IP
192.168.0.101
To port
80
From
port
1152Data
T
C
P
To IP
80.80.12.116
From IP
81.1.30.9
To port
80
From
port
1152
Inside network NAT table Outside network
Portnumber
PAT finds unused Port
InternetSOHO Router
with NAT and PAT
Inside net: 192.168.0.0/24
From
192.168.0.101:1152
Protocol
TCP
To
80.80.12.116:80
From
81.1.30.9:1152
To
80.80.12.116:80
NAT tabelProtocol
TCP
192.168.0.102:1152TCP 80.80.12.116:80 81.1.30.9:2345 80.80.12.116:80TCP
NAT tabel
101
102
103
1
WAN address
Ydre net: 81.1.30.9/32
80.80.12.116
194.255.14.8
DataT
C
P
To IP
80.80.12.116
Indre Ydre
From IP
192.168.0.102
To port
80
From
port
1152Data
T
C
P
To IP
80.80.12.116
From IP
81.1.30.9
To port
80
From
port
2345
Inside network NAT table Outside network
Unused port on outside found
PAT sikrer korrekt levering
InternetSOHO Router
with NAT and PAT
Inside net: 192.168.0.0/24
From
192.168.0.101:1152
Protocol
TCP
To
80.80.12.116:80
From
81.1.30.9:1152
To
80.80.12.116:80
NAT tabelProtocol
TCP
192.168.0.102:1152TCP 80.80.12.116:80 81.1.30.9:2345 80.80.12.116:80TCP
NAT tabel
101
102
103
1
WAN adresse
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
DataT
C
P
To IP
192.168.0.102
Indre Ydre
From IP
80.80.12.116
To port
1152
From
port
80Data
T
C
P
To IP
81.1.30.9
From IP
80.80.12.116
To port
2345
From
port
80
Inside network NAT table Outside network
Always unique ports
InternetSOHO Router
with NAT and PAT
Inside net: 192.168.0.0/24
From
192.168.0.101:1152
Protocol
TCP
To
80.80.12.116:80
From
81.1.30.9:1152
To
80.80.12.116:80
NAT tabelProtocol
TCP
192.168.0.102:1152TCP 80.80.12.116:80 81.1.30.9:2345 80.80.12.116:80TCP
192.168.0.101:1153TCP 80.80.12.116:80 81.1.30.9:1153 80.80.12.116:80TCP
NAT tabel
101
102
103
1
WAN address
Outside net: 81.1.30.9/32
80.80.12.116
194.255.14.8
DataT
C
P
To IP
192.168.0.101
Indre Ydre
From IP
80.80.12.116
From
port
80Data
T
C
P
To IP
81.1.30.9
From IP
80.80.12.116
From
port
80
To port
1153To port
1153
Inside network NAT table Outside network
Important if for example
two browser windows
connect to same server
DNS SERVERRoles and functions
DNS server roles
• Master DNS server
– Administrate DNS zones• For example: ascom.se
• Slave DNS server
– Receives zone information from master server• Acts as redundant server and ofloads the master
• Caching DNS server
– Caches (stores) information learnt• Flushes information when TTL – Time to Live - expires
Company example
DHCP Client
Net: 194.182.53/24 1 3
DHCP Server
DNS Configuration:
WWW.ASCOM.SE is 194.182.53.2
DNS.ASCOM.Se is 194.182.53.3
Forward unknown requests to 192.71.13.54
Router/
Firewall
Internet
DNS server
192.71.13.54
DHCP Client
WEB server DNS Server
2
4
DHCP Configuration:
Ip address scope: 194.182.53.10 to 194.182.53.199
Subnet mask: 255.255.255.0
DNS server: 194.182.53.3
Default gateway: 194.182.53.1
DNS zone records
• A - Address record
– An A-record is used to give a host a name• For example www.ascom.se
• Default nslookup type=A
DNS zone records
• SOA - Start Of Authority record
– Name and mail address on the authority of the domain
DNS zone records
• NS - Name Server record
– Shows DNS servers for the domain.
The order of the servers are
Changed for each reply for
Allowing load sharing to the
DNS servers.
DNS zone records
• MX – Mail eXchange
– Shows Mail servers for the domain.• The ascom.se domain has two mail servers
– Mail.ascom.se and mail.ascom.nl
– The mailserver with lowest preference has highest priority and will beused first. If unreachable the next lowest preference is tried.
• The IP address of the mail server(s) is found using a A-record lookup
Windows DNS Server
• Windows server version 2003, 2008 and 2012 has intutiveDNS server management tools.
• mail.mydomain.com A record points to 83.90.47.90
• www.mydomain.com A record points to 83.90.47.30
• mail.mydomain.com MX record (preference=10)
• mail.myotherdomain.dk MX record (preference=20)
DHCP SERVER
Server 1DNS
DHCP
Server 2FIL PRINT
1
192.168.0.2
Building 2
Client
192.168.200.0/24
1
R1
Internet
DHCP172.30.0.0/30
1 2
Building 1
192.168.0.3
DHCP
DHCP
SW1
Client
254
SW2
Building 3
192.168.210.0/24
1
6
DHCP
SW3
2
R3R2
Client
172.30.0.4/305
Printer
DHCP
Client
DHCP example
DHCP Client
Net: 194.182.53/24 1
3
DHCP Server
Static IP address
DHCP lease pool on server:
IP address range: 194.182.53.10 - 194.182.53.199
Subnet mask: 255.255.255.0
DNS server: 192.71.13.54
Default gateway: 194.182.53.1
ROUTER
Internet
DNS server
192.71.13.54
DHCP Client
DHCP Client DHCP
Server(s)
Network
1. DHCP-Discover
3. DHCP-Request
4. DHCP-Ack
2. DHCP-Offer
DHCP server
• The DHCP Discover packet is a broadcast
and is limited to OSI layer 2.
– Blocked by Routers
• Professional routers can function as
DHCP-relays relaying the DHCP packets
from a physical network to the DHCP
server
DHCP Relayone server many logical networks
Server 1DNS
DHCP
Server 2FIL PRINT
1
192.168.0.2
Building 2
Client
192.168.200.0/24
1
R1
Internet
DHCP172.30.0.0/30
1 2
Building 1
192.168.0.3
DHCP
DHCP
SW1
Client
254
SW2
Building 3
192.168.210.0/24
1
6
DHCP
SW3
2
R3R2
Client
172.30.0.4/305
Printer
DHCP
Client
DHCP relay configured on
Router interface facing the
DHCP clients to forward incoming .
DHCP packets to 192.168.0.2
DHCP relay configured is on
router interfaces facing the
DHCP clients to forward incoming .
DHCP packets to 192.168.0.2
DHCP options
• DHCP options is information the DHCP
clients needs beside the IP Address and
the subnet mask.
• DHCP options examples
– Option 003: IP Address of default gateway
– Option 015: IP Address of DNS server(s)
– Option 150: IP Address of TFTP server
• Trival File Transfer Protocol
– Option 042: IP Address of NTP server
• Network Time Protocol
DHCP options
• Windows DHCP server options
configuration example
• TFTP servers are often used to store IP
phones configuration files.
Configuring IP phones
Net: 194.182.53/24 1
3
DHCP Server
Router/
Firewall
Internet
DNS server
192.71.13.54
DHCP Client
FTP server IP Telephone
server
2
4
DHCP Configuration:
Ip address scope: 194.182.53.10 to 194.182.53.199
Subnet mask: 255.255.255.0
DNS server: 192.71.13.54
Default gateway: 194.182.53.1
Option 150 (TFTP) 194.182.53.2
1 2ABC
3DEF
4 5JKL
6MNOGHI
7 8TUV
9WXYZPQRS
* 0OPER
#
7960CISCO IP PHONE
imessages directories
settingsservices
1 2ABC
3DEF
4 5JKL
6MNOGHI
7 8TUV
9WXYZPQRS
* 0OPER
#
7960CISCO IP PHONE
imessages directories
settingsservices
IP Telephone
DHCP ClientIP Telephone
DHCP Client
DHCP Client
Thank you for listening
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