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Networking for server IT specialists
Zdeněk Filipec
Network Engineer
Table of content
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Networking models ISO/OSI, TCP/IP
ISO/OSI layers 4,3 and 2
Life cycle of PDU
Routing table
Port aggregation
VLANs and trunks
Basic troubleshooting
Practical session: sniffing
Networking for server IT specialists
Legend
Networking for server IT specialists: Legend
Comparing ISO/OSI x TCP/IP model
Networking for server IT specialists: Networking models ISO/OSI, TCP/IP
Application layer
• Provides the interface between the applications we use
to communicate and the underlying network over which
our messages are transmitted. Application layer
protocols are used to exchange data between programs
running on the source and destination hosts.
• Presentation layer: coding, compression, encryption
• Session layer: create and maintain dialogs between
source and destination applications
Networking for server IT specialists: Application layer
Application layer protocols
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Domain Name Service Protocol (DNS) is used to resolve Internet names to IP addresses.
Hypertext Transfer Protocol (HTTP) is used to transfer files that make up the Web pages of the
World Wide Web.
Simple Mail Transfer Protocol (SMTP) is used for the transfer of mail messages and attachments.
Telnet, a terminal emulation protocol, is used to provide remote access to servers and networking
devices.
File Transfer Protocol (FTP) is used for interactive file transfer between systems
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Application layer
applications
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Applications, services
Networking for server IT specialists: Application layer
Transport layer
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Segmenting Data
Reassembling
Segments
Identifying the
Applications
Networking for server IT specialists: Transport layer
Transport layer
Networking for server IT specialists: Transport layer
Transport layer
Networking for server IT specialists: Transport layer
Ports
Networking for server IT specialists: Transport layer
Port numbers
Networking for server IT specialists: Transport layer
Source / destination port
Networking for server IT specialists: Transport layer
Command netstat
• All active connections
– Parameters:
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-a
-r
-v
-n
all connection and listening servers
routing table
detailed output
connections in numeric format (no DNS)
– Only windows:
• -p <procotol> just specified protocol (tcp, udp,…)
• -b
name of the program using given socket
– Only Unix
• -u | -t just specified protocol (tcp, udp,…)
• -p
PID and program name using the socket
Networking for server IT specialists: Transport
Headers
Networking for server IT specialists: Transport layer
three-way handshake
Networking for server IT specialists: Transport layer
TCP communication
Networking for server IT specialists: Transport layer
Network layer
Networking for server IT specialists: Network layer
Network layer
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Connectionless – No connection is established before sending data packets
Best effort (unreliable) – No overhead is used to guarantee packet delivery
Media Independent – Operates independently of the medium carrying the data
Networking for server IT specialists: Network layer
Header
Networking for server IT specialists: Network layer
IPv4 address
Networking for server IT specialists: Network layer
Subnet mask
Networking for server IT specialists: Network layer
Binary x decimal
Networking for server IT specialists: Network layer
Address types
Network address - The address by which we refer to the network
Broadcast address - A special address used to send data to all hosts in the network
Host addresses - The addresses assigned to the end devices in the network
Networking for server IT specialists: Network layer
Types of communication
Unicast - the process of sending a packet from one host to an individual host
Broadcast - the process of sending a packet from one host to all hosts in the network
Multicast - the process of sending a packet from one host to a selected group of hosts
(PIM, IGMP)
Networking for server IT specialists: Network layer
IPv4 classes
Private ranges
localhost
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10.0.0.0/8
172.16.0.0/16 – 172.31.0.0/16
192.168.0.0/16
Automatic Windows address
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Networking for server IT specialists: Network layer
127.0.0.1
169.254.0.0/16
Network layer
Networking for server IT specialists: Network layer
IPv6
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IPv6 conventions use 32 hexadecimal numbers, organized into 8 quartets of 4 hex digits
separated by a colon, to represent a 128-bit IPv6 address, for example:
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Writing or typing 32 hexadecimal digits, although more convenient writing or typing
128binary digits, can still be a pain. To make things a little easier, two conventions allow
you to shorten what must be typed for an IPv6 address:
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2340:1111:AAAA:0001:1234:5678:9ABC
Omit the leading 0s in any given quartet.
Represent one or more consecutive quartets of all hex 0s with “::” but only for one such occurrence
in a given address.
For example, consider the following address. The bold digits represent digits in which the
address could be abbreviated:
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FE00:0000:0000:0001:0000:0000:0000:0056
• FE00::1:0:0:0:56
• FE00:0:0:1::56
Networking for server IT specialists: Network layer (IPv6)
IPv6
Networking for server IT specialists: Network layer (IPv6)
IPv6 stateless autoconfig
Host PC1, using stateless autoconfig, sends the RS message as an IPv6 multicast message
destined to all IPv6 routers on the local link. The RS asks all routers to respond to the questions
“What IPv6 prefix(s) is used on this subnet?” and “What is the IPv6 address(s) of any default
routers on this subnet?” The figure also shows R1’s response (RS), listing the prefix
(2340:1111:AAAA:1::/64), and with R1’s own IPv6 address as a potential default router.
Networking for server IT specialists: Network layer (IPv6)
IPv6 stateless autoconfig
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For example, the following two lines list a host’s MAC address, and corresponding EUI-64 format
Interface ID, assuming the use of an address configuration option that uses the EUI-64 format:
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0034:5678:9ABC
0234:56FF:FE78:9ABC
Note: To change the seventh bit (left-to-right) in the example, hex 00 converts to binary 00000000, change the
seventh bit to 1 (00000010), convert back to hex, for hex 02 as the first two digits.
Networking for server IT specialists: Network layer (IPv6)
IPv6 address types
Networking for server IT specialists: Network layer (IPv6)
Data link layer
Networking for server IT specialists: Data link layer
Data link layer
Networking for server IT specialists: Data link layer
Duplex
Networking for server IT specialists: Data link layer
MAC address
Networking for server IT specialists: Data link layer
Addressing
Networking for server IT specialists: Data link layer
Ethernet
Networking for server IT specialists: Data link layer
Address resolution protocol (ARP)
Networking for server IT specialists: ARP
ARP table
Windows
ARP parameters
-a all entries in ARP cache
-s <IP> <MAC> manual adding of static entry
-d <IP> deleting the entry from ARP
In Unix plus:
-v detailed output
-n in numeric format (without DNS
translation)
C:\Users\IBM_ADMIN>arp -a
Interface: 192.168.1.189 --- 0xe
Internet Address
Physical Address
192.168.1.1
d8-50-e6-60-1f-a0
192.168.1.83
e0-3f-49-1e-20-e8
192.168.1.255
ff-ff-ff-ff-ff-ff
224.0.0.252
01-00-5e-00-00-fc
224.1.1.1
01-00-5e-01-01-01
255.255.255.255
ff-ff-ff-ff-ff-ff
Unix
# arp -a
IP address
172.16.1.3
172.16.1.2
172.16.2.4
Networking for server IT specialists: ARP
HW type HW address
10Mbps Ethernet 00:00:C0:5A:42:C1
10Mbps Ethernet 00:00:C0:90:B3:42
10Mbps Ethernet 00:00:C0:04:69:AA
Type
dynamic
dynamic
static
static
static
static
Encapsulation / decapsulation
Networking for server IT specialists: Encapsulation
Router
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The primary responsibility of a router is to direct packets destined for local and
remote networks by:
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Determining the best path to send packets
Forwarding packets toward their destination
The router uses its routing table to determine the best path to forward the packet.
When the router receives a packet, it examines its destination IP address and
searches for the best match with a network address in the router's routing table. The
routing table also includes the interface to be used to forward the packet.
Networking for server IT specialists: Routing table
Routing table
Networking for server IT specialists: Routing table
Routing table
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Windows:
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route print
http://technet.microsoft.com/en-us/library/cc779122%28v=ws.10%29.aspx
http://technet.microsoft.com/en-us/library/cc754012%28v=ws.10%29.aspx
Unix
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route –n
http://www.cyberciti.biz/faq/what-is-a-routing-table/
Networking for server IT specialists: Routing table
Default route
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Windows:
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route add 0.0.0.0 mask 0.0.0.0 192.168.1.1
Unix
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route add default gw 191.255.255.1 eth0
Networking for server IT specialists: Routing table
Switch
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Dedicated bandwidth to each port
Collision-free environment
Full-duplex operation
Networking for server IT specialists: Switch
Life cycle of PDU
Networking for server IT specialists: Life cycle of PDU
Life cycle of PDU
Networking for server IT specialists: Life cycle of PDU
Port aggregation
Networking for server IT specialists: Port aggregation
Port aggregation
Networking for server IT specialists: Port aggregation
Port aggregation
Two to eight links of either Fast
Ethernet (FE), Gigabit Ethernet (GE),
or 10-Gigabit Ethernet (10GE) are
bundled as one logical link of Fast
EtherChannel (FEC), Gigabit
EtherChannel (GEC), or 10-Gigabit
Etherchannel (10GEC), respectively.
This bundle provides a full-duplex
bandwidth of up to 1600 Mbps (eight
links of Fast Ethernet), 16 Gbps
(eight links of Gigabit Ethernet), or
160 Gbps (eight links of 10-Gigabit
Ethernet).
Networking for server IT specialists: Port aggregation
Port aggregation
Networking for server IT specialists: Port aggregation
Port aggregation
Configuration
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Unix (bonding)
– http://backdrift.org/howtonetworkbonding
– http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/98469ios-etherchannel.html
Windows
– http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/98469ios-etherchannel.html
Networking for server IT specialists: Port aggregation
VLANs
Networking for server IT specialists: VLANs
VLANs
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A VLAN allows a network administrator to create groups of logically
networked devices that act as if they are on their own independent
network, even if they share a common infrastructure with other VLANs
A VLAN is a logically separate IP subnetwork. VLANs allow multiple IP
networks and subnets to exist on the same switched network.
VLAN types:
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Data, Voice, Management, Native
Trunk
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A trunk is a point-to-point link between two network devices that carries more
than one VLAN. A VLAN trunk allows you to extend the VLANs across an entire
network.
Networking for server IT specialists: VLANs
Trunk link
Networking for server IT specialists: VLANs
Trunk link
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Networking for server IT specialists: VLANs
The frame header does not contain
information about which VLAN the frame
should belong to.
Subsequently, when Ethernet frames are
placed on a trunk they need additional
information about the VLANs they belong
to. This is accomplished by using the
802.1Q encapsulation header. This header
adds a tag to the original Ethernet frame
specifying the VLAN to which the frame
belongs.
Intra-VLAN communication
Networking for server IT specialists: VLANs
Practical session
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Basic troubleshooting
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Interface up/down
ping (ping GW)
IP configuration (ipconfig x ifconfig)
traceroute
Sniffing
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ICMP
ARP
DHCP
DNS
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nslookup x dig
HTTP
three way handshake
Networking for server IT specialists: Practical session
Sniffing DHCP
Networking for server IT specialists: Sniffing
Questions
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Thank you for the attention
Networking for server IT specialists