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1
UNIX Networking
2
Section Overview
TCP/IP Basics
TCP/IP Configuration
TCP/IP Network Testing
Dynamic Host Config Protocol (DHCP)
Wireless Networking
3
TCP/IP Protocol Stack
Physical Layer (media)Physical Layer (media)
Link Layer (Device Drivers)Link Layer (Device Drivers)
Network Layer (IP)Network Layer (IP)
Transport Layer (TCP,UDP)Transport Layer (TCP,UDP)
Application (FTP, HTTP, DNS)Application (FTP, HTTP, DNS)
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EE IPIP T/UT/U
TCP/IP Packet Encapsulation
UTP/PSTNUTP/PSTN
Ethernet/PPPEthernet/PPP
IPIP
TCP/UDPTCP/UDP
ServiceService DataData
DataData
T/UT/U DataData
IPIP T/UT/U DataData
EE
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Connecting to a Network
Hostname and IP Address assignmentConfiguration of hardwareDefault route (gateway) assignmentName Service ConfigurationTesting and troubleshooting
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Hostnames
Uniquely identifies each systemFully Qualified Domain Name hostname.site.domain[.country] Country: 2 letter identifier for country Domain: Type of site (edu, com, org) Site: Unique name of organization Hostname: Unique name of system
hostname: Display or set system name
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IP Addresses
Unique for each connection (interface)Consists of 4 octets (#.#.#.#) Network portion Host portion
Special Addresses Network Address Broadcast Address
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IP Address Classes
ClassClass 11stst Byte Byte FormatFormat Total HostsTotal Hosts
A 0 – 126 N.H.H.H 16 Million
B 128 – 191
N.N.H.H 64 Thousand
C 192 – 239
N.N.N.H 254
D 224 – 239
- (Multicast)
E 240 – 254
- (Experimental)
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Subnet Masks
Splits networks into subnetworksSeparates address into 2 parts 1’s – Network Portion 0’s – Host Portion
Example: Class C Network Address: N.N.N.H Mask: 255.255.255.0 (255 =
11111111) CIDR Notation: N.N.N.H/24
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Interface Configuration
Hardware to connect to networkCommon interfaces Ethernet Modem
Loopback (lo) Interfaceifconfig – View/Configure interface
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Ethernet Addressing
Assigned by manufacturer (hardware)Must be absolutely uniqueAddress format 6 octets in hex (#:#:#:#:#:#) First 3 octets: Manufacturer Identifier Last 3 octets: Card serial number
Used for local network communication
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Translates IP addresses to Ethernet (MAC) addressesTranslates IP addresses to Ethernet (MAC) addresses
Address Resolution Protocol
Who is 10.0.0.3?Who is 10.0.0.3?
10.0.0.110.0.0.1 10.0.0.210.0.0.2 10.0.0.310.0.0.3 10.0.0.410.0.0.4
I am (1:2:3:7:8:9)I am (1:2:3:7:8:9)
arp –a: View the cache
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Connects Networks togetherIf destination not on local network, packets sent through gateway
Default Gateways
route: Display/configure routing
14
RedHat Network Files
/etc/sysconfig/networkHOSTNAME
/etc/sysconfig/network-scripts/ ifcfg-[interface]
BOOTPROTO ONBOOTIPADDR GATEWAYUSERCTL NETMASKNETWORK BROADCAST
ifup/ifdown [interface]
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Name Services
/etc/hosts Local configuration Localhost – 127.0.0.1
/etc/resolv.conf Domain Name Service (DNS) lookup search: domains to search if not FQDN nameserver (3): Nameservers to consult
/etc/nsswitch.conf
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DNS Name Resolution
11
22
33
44 55
667788
host.domain.comhost.domain.com dns.domain.comdns.domain.com dns.iupui.edudns.iupui.edu dns.cs.iupui.edudns.cs.iupui.edu
Root ServerRoot Server Non-RecursiveNon-Recursive
RecursiveRecursive
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Network Testing
Localhost reachabilityHostname reachabilityLocal network reachabilityInternet network reachabilityDNS resolution
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Network tools
ping – Reachability testtraceroute – Routing performancenetstat – Network performance statstcpdump – Packet sniffingnslookup/dig – DNS QueriesConfiguration tools (already discussed)
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Dynamic Host Config Protocol
Client broadcasts a request for an IP address and network informationServer leases address to clientLease must be renewed periodicallyEasy to make global network changesLinux: BOOTPROTO=dhcp
20
Wireless Networks
Extend the networkIncluded in many devices now
Laptops PDAs DSL/Cable Modems
Bandwidth (YMMV!) 802.11b – 11 Mbps 802.11g – 54 Mbps
Set Service Identifier (SSID) Shared “key” between clients and Access Point (AP) Automatically detected vs. assigned
21
Wireless Security Issues
Sniffing / War DrivingBandwidth stealingAccess to private resourcesSecurity Measures Non-broadcasting SSIDs MAC Access Control Lists (ACLs) WEP?
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RedHat ifcfg- Additions
TYPE=Wireless
ESSID=[ssid name]
CHANNEL=[1-11]
MODE=[Auto|Managed|Ad-hoc]
Can set manually with /sbin/iwconfig
23
Virtual Private Networks
Virtual Private NetworkVirtual Private Network
VPNVPNServerServer
ApplicationApplicationServerServer
InternetInternet
24
Point to Point Tunneling Protocol
Based on Point to Point Protocol (PPP) Generic Routing Encapsulation (GRE)
IP HdrIP Hdr GRE HdrGRE Hdr Encrypted GRE BodyEncrypted GRE BodyPPPPPP DataDataTCPTCPIPIP
WeaknessesWeaknesses Poor EncryptionPoor Encryption Session handshaking done in clearSession handshaking done in clear
25
IPSec
Part of IPv6 SpecAuthentication Header (AH)
IPv4 HdrIPv4 Hdr Auth HdrAuth Hdr TCP/UDP Hdr & DataTCP/UDP Hdr & Data
Encapsulating Security Payload (ESP)Encapsulating Security Payload (ESP)
IPv4 HdrIPv4 Hdr ESP HdrESP Hdr Encrypted PayloadEncrypted PayloadDataDataTCP HdrTCP Hdr ESP AuthESP AuthESP TlrESP Tlr
Modes: Transport and TunnelModes: Transport and Tunnel