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 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 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 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: -aall connection and listening servers -rrouting table -vdetailed output -nconnections in numeric format (no DNS) –Only windows: -p 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 Networking for server IT specialists: 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 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 Networking for server IT specialists: Network layer 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 Networking for server IT specialists: Network layer 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 Networking for server IT specialists: Network layer localhost Automatic Windows address /16 Private ranges / /16 – / /16

Network layer Networking for server IT specialists: 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 Networking for server IT specialists: Network layer (IPv6)

IPv6 configuration Networking for server IT specialists: Network layer (IPv6)

IPv6 stateless autoconfig Networking for server IT specialists: Network layer (IPv6) 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 Networking for server IT specialists: Network layer (IPv6) 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 , change the seventh bit to 1 ( ), convert back to hex, for hex 02 as the first two digits.

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 Networking for server IT specialists: ARP Windows C:\Users\IBM_ADMIN>arp -a Interface: xe Internet Address Physical Address Type d8-50-e6-60-1f-a0 dynamic e0-3f-49-1e-20-e8 dynamic ff-ff-ff-ff-ff-ff static e fc static e static ff-ff-ff-ff-ff-ff static Unix # arp -a IP address HW type HW address Mbps Ethernet 00:00:C0:5A:42:C Mbps Ethernet 00:00:C0:90:B3: Mbps Ethernet 00:00:C0:04:69:AA ARP parameters -aall entries in ARP cache -s manual adding of static entry -d 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 Networking for server IT specialists: Routing table

Routing table Networking for server IT specialists: Routing table Windows: –route print – – Unix –route –n –

Default route Networking for server IT specialists: Routing table Windows: –route add mask Unix –route add default gw 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

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 Networking for server IT specialists: 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 Networking for server IT specialists: Port aggregation

Port aggregation Networking for server IT specialists: Port aggregation Configuration Unix (bonding) – – ios-etherchannel.htmlhttp:// ios-etherchannel.html Windows – ios-etherchannel.htmlhttp:// ios-etherchannel.html

VLANs Networking for server IT specialists: VLANs

VLANs Networking for server IT specialists: 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 Networking for server IT specialists: VLANs

Trunk link 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 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

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