Networking for server IT specialists Zdeněk Filipec Network Engineer.

Networking for server IT specialists

Zdeněk Filipec Network Engineer

Table of content

• 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


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

• 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

Networking for server IT specialists: Application layer

Application layer applications

• Applications, services

Transport layer

Networking for server IT specialists: Transport layer

• Segmenting Data• Reassembling

Segments• Identifying the

Applications

Transport layer


Ports


Port numbers


Source / destination port


Command netstat

• All active connections– Parameters:

• -a all connection and listening servers• -r routing table• -v detailed output• -n 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


three-way handshake


TCP communication


Network layer

Networking for server IT specialists: Network layer

Network layer


• 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

Header


IPv4 address


Subnet mask


Binary x decimal


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

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)

IPv4 classes


localhost• 127.0.0.1

Automatic Windows address• 169.254.0.0/16

Private ranges• 10.0.0.0/8• 172.16.0.0/16 – 172.31.0.0/16• 192.168.0.0/16

Network layer


IPv6

Networking for server IT specialists: Network layer (IPv6)

• 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:

– 2340:1111:AAAA:0001:1234:5678:9ABC

• 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:

– 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:

– FE00:0000:0000:0001:0000:0000:0000:0056• FE00::1:0:0:0:56• FE00:0:0:1::56

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.

IPv6 stateless autoconfig


• 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:

– 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.

IPv6 address types


Data link layer

Networking for server IT specialists: Data link layer

Duplex


MAC address


Addressing


Ethernet


Address resolution protocol (ARP)

Networking for server IT specialists: ARP

ARP table

Networking for server IT specialists: ARP

Windows

C:\Users\IBM_ADMIN>arp -a

Interface: 192.168.1.189 --- 0xe

Internet Address Physical Address Type

192.168.1.1 d8-50-e6-60-1f-a0 dynamic

192.168.1.83 e0-3f-49-1e-20-e8 dynamic

192.168.1.255 ff-ff-ff-ff-ff-ff static

224.0.0.252 01-00-5e-00-00-fc static

224.1.1.1 01-00-5e-01-01-01 static

255.255.255.255 ff-ff-ff-ff-ff-ff static

Unix

# arp -a

IP address HW type HW address

172.16.1.3 10Mbps Ethernet 00:00:C0:5A:42:C1

172.16.1.2 10Mbps Ethernet 00:00:C0:90:B3:42

172.16.2.4 10Mbps Ethernet 00:00:C0:04:69:AA

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)

Encapsulation / decapsulation

Networking for server IT specialists: Encapsulation

Router

Networking for server IT specialists: Routing table

• The primary responsibility of a router is to direct packets destined for local and remote networks by:

– 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.

Routing table


Routing table


• Windows: – 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– route –n– http://www.cyberciti.biz/faq/what-is-a-routing-table/

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

http://www.cyberciti.biz/faq/what-is-a-routing-table/

Default route


• Windows: – route add 0.0.0.0 mask 0.0.0.0 192.168.1.1

• Unix– route add default gw 191.255.255.1 eth0

Switch

Networking for server IT specialists: Switch

• Dedicated bandwidth to each port

• Collision-free environment

• Full-duplex operation

Life cycle of PDU

Networking for server IT specialists: Life cycle of PDU

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).

Port aggregation


Port aggregation


Configuration

• Unix (bonding)

– http://backdrift.org/howtonetworkbonding

– http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/98469-ios-etherchannel.html

• Windows

– http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/98469-ios-etherchannel.html

http://backdrift.org/howtonetworkbonding

http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/98469-ios-etherchannel.html




VLANs

Networking for server IT specialists: VLANs

VLANs


• 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:– Data, Voice, Management, Native

• Trunk– 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.

Trunk link


Trunk link


• 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


Practical session

Networking for server IT specialists: Practical session

• Basic troubleshooting– Interface up/down– ping (ping GW)– IP configuration (ipconfig x ifconfig)– traceroute

• Sniffing– ICMP – ARP– DHCP– DNS

• nslookup x dig

– HTTP– three way handshake

Sniffing DHCP

Networking for server IT specialists: Sniffing

• ...


Thank you for the attention

Questions

Networking for server IT specialists Zdeněk Filipec Network Engineer.

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