Networking For Application Developers by Roy Kim

IT Networking for Application DevelopersPresenter: Roy [email protected]: roykimsharepoint.wordpress.com

Agenda• Benefits of IT Networking Knowledge• Networking Fundamentals• Troubleshooting Network Devices• Troubleshooting Tools

[email protected]@wordpress.com

Benefits of Networking Knowledge• Interface with IT administrators and IT architects.

Know how to ask the right questions.

• Understand development machine and testing environments. Faster issue/resolution cycles with IT Fix your own problems

• Become a well-rounded Technology Architect Core fundamental Design application architecture with IT touch points in mind


Network Diagram

SwitchSwitch

HostsRouter

DMZ

Subnet

Internet

Firewall Security


Network Fundamentals• Node

Any device on a network• Host

Participate in applications in a client server model on a network.• Switch

Routing traffic within a network between hosts.• Subnet

A partition of a network that share the same network ID or subnet prefix. A grouping of network traffic into sub networks.Mitigate network congestion.

• Router Routing IP traffic between networks and subnets


Network Fundamentals• Domain Name Resolution (DNS) Server

Host Name Resolution service Translate host name to IP Address DNS client resolver cache

• Dynamic Host Configuration Protocol (DHCP) Server Automatic assignment of an IP address to a network device. Client IP reservation - Offers static assignment

e.g. Network Printers


Network Fundamentals• Firewall

Allow or deny network traffic on the inbound or outbound communication

Network Security Management Packet Filter Application firewall Network address translation Proxies Load Balancer E.g. Microsoft Threat Management Gateway


TCP/IP Protocol Suite• Transmission Control Protocol/Internet Protocol• The suite of communications protocols used to connect hosts on the Internet.


Hosts: TCP/IP ConfigurationIP Address

MAC Address

Subnet Mask

Default Gateway

DNS Server

DHCP Enabled

DHCP Server

192.168.1.100

00-50-56-C0-00-01

255.255.255.0

192.168.1.1

192.168.2.101

Yes

192.168.2.200


SubnettingDMZ

Internet192.168.1.128

192.168.1.0 192.168.1.64

Subnet Mask 255.255.255.192 or CIDR /26Network ID 192.168.1.0

10.21.128.1

192.168.1.2

192.168.1.3

192.168.1.4

192.168.1.5

Hosts:192.168.1.66-126

Hosts:192.168.1.29-190

192.168.1.1

192.168.1.65

192.168.1.129


Subnetting

Binary form Dot-decimal notation

IP address 11000000.10101000.00000101.10000010 192.168.5.130

Subnet mask 11111111.11111111.11111111.00000000 255.255.255.0

Network prefix 11000000.10101000.00000101.00000000 192.168.5.0

Host part 00000000.00000000.00000000.10000010 0.0.0.130

Binary form Dot-decimal notation

IP address 11000000.10101000.00000101.10000010 192.168.5.130

Subnet mask 11111111.11111111.11111111.11000000 255.255.255.192

Network prefix 11000000.10101000.00000101.10000000 192.168.5.128

Host part 00000000.00000000.00000000.00000010 0.0.0.2


Troubleshooting Areas• Network Interface

IP Address (DHCP) ARP Cache

• Subnet or Routers or Host Route table

• Host Name Resolution DNS Server DNS client resolver cache Host file

• Firewall


Troubleshooting Connectivity• IP Addressing

To display, ipconfig /all netsh interface ip show config

To verify, ping loopback address 127.0.0.1 ping <host IP Address>

To clear IP address, ipconfig /release To get new IP address from DHCP, ipconfig /renew IP conflict scenario To clear, arp -d


• ipconfig


Troubleshooting Connectivity• Arp cache

To display, arp –a

To clear, arp -d


Troubleshooting Connectivity• Subnet Mask

To display, ipconfig /all Can set manually in Local Area Connection properties.

• Default Gateway To display, ipconfig /all Can set manually in Local Area Connection properties.


Troubleshooting Connectivity• Verify reachability to another host

ping <remote IP address>

• Verify Route Table entries To display, route print

To clear, route –f


Troubleshooting Connectivity• Verify reachability for intermediate routers

tracert <remote IP address>

pathping <remote IP address>


Troubleshooting Host Name Resolution

• DNS Server• Verify DNS server response, nslookup <hostname/FQDN>• Verify DNS Server setting, ipconfig /all• ping <DNS server IP>• ipconfig /registerdns

• DNS client resolver cache• To display, ipconfig /displaydns | more• ipconfig /flushdns

• Flushes the contents of the DHS resolver cache on the local computer. Pre-loads any entries in the HOSTS file into the cache.

• NetBIOS • To display cache, nbtstat -c

• Host file Location: %SystemRoot%\system32\drivers\etc\hosts DNS client resolver cache includes host file entries


Troubleshooting Firewall Rules

Blocks inbound and/or outbound tcp/ip traffic Client side vs Server side firewall Verify communication/connectivity in front or behind

firewall. Verify if other clients can connect View firewall rules


Troubleshooting TCP Ports

Display ports’ state and PID, netstat –ano Display applications and ports listening, netstat –b

Verify tcp port connectivity, telnet <IP address> <TCP Port>


Tools SummaryTool DescriptionArp Allows viewing and editing of the Address Resolution Protocol (ARP) cache.Hostname Displays the host name of the computer.Ipconfig Displays the current TCP/IP configuration for both IPv4 and IPv6. Also used to

manage Dynamic Host Configuration Protocol (DHCP)-allocated IPv4 address configurations, display or flush the DNS client resolver cache, and register DNS names.

Netsh Configuration tool for many network services. For each network service, there is a context containing commands specific for that service. For the netsh interface ip contexts, displays and administers TCP/IP protocol settings on either the local computer or a remote computer.

Netstat Displays protocol statistics and information on current TCP connections.Nslookup Performs DNS queries and displays the results.Ping Sends Internet Control Message Protocol (ICMP) Echo or Internet Control

Message Protocol for IPv6 (ICMPv6) Echo Request messages to test reachability.

Route Allows viewing of the IPv4 and IPv6 routing tables and editing of the IPv4 routing table.

Tracert Sends ICMP Echo or ICMPv6 Echo Request messages to trace the network route taken by IPv4 or IPv6 packets to a specific destination.

Pathping Sends ICMP Echo or ICMPv6 Echo Request messages to trace the route an IPv4 or IPv6 packet takes to a destination and displays information on packet losses for each router and link in the path.

Event Viewer Records errors and events.Performance Logs and Alerts

Logs TCP/IP core protocol performance and sends alerts (the SNMP service must be installed).

Network Monitor Captures and displays the contents of TCP/IP packets sent to and from computers running Windows Server 2003.

Telnet Tests TCP connection establishment between two nodes.


Networking For Application Developers by Roy Kim

Technology

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