Networking

Private IP range

 

ipv4-address

Automatic Private IP Addressing [ APIPA ]

169.254.1.1 to 169.254.255.254

For APIPA, clients will be assigned with Class B subnet mask [255.255.0.0]. If a client has APIPA address it will check for DHCP server every 5 minutes. If available it will get a DHCP IP address.

APIPA is assigned by the client on its own. In order not to get duplicate APIPA, clients will broadcast itself (IP address etc) in the network.

Loopback address

127.0.0.1 to 127.255.255.255

The loopback interface has no hardware associated with it, and it is not physically connected to a network. The loopback interface allows IT professionals to test IP software without worrying about broken or corrupted drivers or hardware.

IP Addressing

IP V4 address classes
Class Network bits Host bits Decimal address subnet mask No. of possible hosts No. of possible N/W
A 8 bits 24bits 1-127.255.255.255 255.0.0.0 16M+ 128
 B 16 bits 16bits 128 – 191 255.255.0.0 65,534 hosts 16,384
 C 24bits 8 bits 192-223 255.255.255.0 254hosts 20,97,150
 D Reserved for Multicasting 224-239 NA
 E Reserved for R & D 240-255 NA
127 – Loop back address

ipv4-vs-ipv6

v4_v6_table

IPv6

  • Has a 128 bit address
  • Does not require subnet mask
  • Written in colon-hexadecimal notation. Uses 8 16-bit hexadecimal numbers separated by colons. Hexadecimal numbers made up of 0-9 and a-f.
  • Ex: 20f3:ab94:acc8:0000:0000:1894:1000:a83f
  • IPv6 abbreviated format
  • 20f3:ab94:acc8:0000:0000:1894:1000:a83f and 20f3:ab94:acc8::1894:1000:a83f are same

Double Colon notation for

20f3:ab94:acc8:0000:0000:1894:1000:a83f is

20f3:ab94:acc8::1894:1000:a83f

CIDR Notation for

20f3:ab94:acc8:0000:0000:1894:1000:a83f is

20f3:ab94:acc8:0000:0000/80

contracted form:

20f3:ab94:acc8::/80

80 indicates first 80-bits is Network ID

IPv6 has 5 address types:

  1. Global Unicast Address – Equivalent to public IPv4
  2. Link-Local Unicast Address – Self generated IP address, automatically created by client.
  3. Unique Local Unicast Address – Equivalent to class A, B and C private network address of IPv4. Cannot be used for internet.
  4. Multicast Address – Begin with Binary value 11111111 or FF
  5. Anycast Address – Identifies routers within an address range.

IPv6 address can be allocated in 3 ways:

  1. Dynamic allocation – Through a DHCP v6 server
  2. Self-allocation (stateless address auto configuration) – If DHCP v6 server is not available, client will allocate IP v6 address on its own. Similar to APIPA.
  3. Manual allocation

Default duration of DHCP scope is 8 days (Windows 2012 R2 server)

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IP Subnet

https://theamvj.wordpress.com/2016/03/20/ip-subnets/

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Admin IP – Server IP

Real IP – Load balanced IP (it could be an IP on the server but communicates with the Network device for load balance)

Netmask

I have got this rather excellent Netmask address prefix from http://www.gadgetwiz.com/network/netmask.html

Netmask

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NIC Teaming (NIC – Network Interface Card / Ethernet card)

NIC Teaming means a single VM or server is allocated with multiple NICs and they work as one single Virtual NIC.

Advantages:

  • Better performance
  • Fault tolerance

NIC teaming can be done at OS level. Microsoft calls NIC teaming as Load balancing / Failover (LBFO). Windows 2012 server supports upto 32 NIC. These 32 NICs can be different. Earlier Windows OS variants needs same NICs.

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Network Address Translation (NAT)

NAT allows hosts with private IP address to access Internet through proxy devices.

NAT

TCP (Transmission Control Protocol) vs UDP (User Datagram Protocol)

UDP is better than TCP where performance is the requirement. And due to performance issues, a UDP packet used for DNS is limited to 512 bytes, if your payload goes above 512 bytes, then TCP will be used.

TCP involves very high overhead, because it includes multiple steps and procedures to establish a TCP connection, that can slow the entire process.

More details:

http://www.slashroot.in/dns-root-servers-most-critical-infrastructure-internet