1. IP Networks and Routing
Oakton Community College
CIS 238

2. LINUX Network Setup Commands: - ip - ifconfig
- ethtool, sysctl (see sysctl.conf) ,
see ndd on non-LINUX systems
- service network start/stop
Datasets:
- /etc/sysctl.conf, sysctl.d
- /etc/sysconfig/network-scripts

3. IP Addressing Requirements
Network address
NetMask
Gateway address
Static or DHCP

4. IP V4 addressing IP addresses
Consist of 32 bits normally expressed either as four binary octets separated by periods or as four sets of decimal numbers separated by periods
Contain a network ID and a host ID defined by the subnet mask
If more than local addressing must also supply a Gateway address to the rest of the world.

5. IPv4 Address Classes Five different classes of IP addresses
First three reserve a certain portion of the 32 bits available for the network ID and the host ID
Last two are used in special situations only

6. Subnet Masks
32-bit numbers used to determine the portion of an IP address that represents the network ID and the host ID
Place a 1 in bit positions that correspond to network ID bits and a zero in bits that represent host ID bits
The host can perform a logical AND function to determine if a destination IP address is on a local network or a remote network

7. IP Subnetting
Process of borrowing host bits to increase the number of network bits
Allows administrators to better utilize IP networks that are either assigned to them from the Internet Assigned Numbers Authority (IANA) public IP addresses or from the private address space defined by RFC 1918: /8, / /16, /16

8. Network Routing Routing On an IP network:
Process of moving information along a path from a source to a destination on a network or between networks
On an IP network:
Source and destinations are called hosts
Information is fragmented into packets that are transferred between these hosts

9. Direct (Local) Routing
Direct Routing (ARP only). Local delivery is via MAC Address contained in ARP table.

10. Indirect Routing Source and destination hosts are not on the
same network segment
Packets must pass
through a router,
a physical link
between two or
more networks

11. Indirect Routing IP determines location of routers in one of two ways:
Consults a locally maintained routing table, a list of networks the system knows about and the IP addresses of routers that packets must pass through to get to those networks
Uses a default gateway (if network is not found on the static routing table)
Either way, the designated router for the address is on the local network and is ARP’ed for like any local host.
A route consists of:
a) network address
b) subnet mask
c) next hop gateway address.

12. Routers
Routers
A physical device used to connect a number of network segments
Can be dedicated pieces of hardware, or can be computers with more than one network adapter card, each connected to a different network segment

13. Static and Dynamic Routers
Static routers
Router to which routes must be added manually.
Provide an entry in the routing table for every network on the internetwork
Configure each router with a default gateway
Note: every host on a IP network is a static router, if only for itself.
Dynamic routers
Routers that automatically share their routing information with other routers on the network using a routing protocols such as RIP, OSPF, EIGRP or BGP

14. Routing Protocols
Standard language that lets dynamic routers exchange routing information
Basic types:
- Distance (RIP, BGP)
- Link State(OSPF) Both (EIGRP)
- Interior: RIP, OSPF, IGRP
- Exterior: EGP, BGP, EIGRP
Link state protocols separate networks into areas with common network information
Autonomous system
One set of networks and routers all under the same administration or group

15. IPv4 Header

16. Route Debugging arp (-a) ping / pathping ipconfig /all, ifconfig -a
tracert, traceroute
netstat –rn
route

17. IPv4 Protocols Internet Control Message Protocol (ICMP)
Handles communication error messages
Internet Group Management Protocol (IGMP)
Provides functionality for multicasting
Internet Protocol (IP)
Connectionless, layer three protocol
Determines proper routing within multiple networks
Address Resolution Protocol (ARP)
Maps a known IP address to a Media Access Control (MAC) layer address

18. IPv4 protocols (2) Multicast Routing Protocols
Maintaining Multicast Routing Table
E.g. DVMRP, MOSPF, CBT, PIM
Exterior Routing Protocols (Inter-AS)
E.g. BGP (Border Gateway Protocol)
Quality-of-Service Frameworks
Integrated Service (ISA, IntServ)
Differentiated Service (DiffServ)

19. IPv4 to IPv6
Changed
Removed

20. Network Layer in v4 & v6

21. IPv6 Addressing Model Addresses are assigned to interfaces, not hosts
Interface expected to have multiple addresses
Addresses have scope
Link-Local
Site-Local  Unique Local
Global

22. Text Representation of Address
Colon-Hex
3ffe:3600:2000:0800:0248:54ff:fe5c:8868
Compressed Format:
3ffe:0b00:0c18:0001:0000:0000:0000:0010
becomes 3ffe:b00:c18:1::10

23. Address Type Prefixes

24. Global Unicast Address
Global routing prefix
A (typically hierarchically-structured) value assigned to a site (a cluster of subnets/links)
Subnet ID
An identifier of a subnet within the site
Interface ID
Constructed in Modified EUI-64 format

25. MAC to IPv6 mapping

26. Site-Local Address
Meaningful only in a single site zone, and may be re-used in other sites
Equivalent to the IPv4 private address space
Address are not automatically configured and must be assigned
Prefix= FEC0::/48

27. Link-Local Address
Meaningful only in a single link zone, and may be re-used on other links
Link-local addresses for use during auto-configuration and when no routers are present
Required for Neighbor Discovery process, always automatically configuration
An IPv6 router never forwards link-local traffic beyond the link
Prefix= FE80::/64

28. Special IPv6 Address Loopback address (0:0:0:0:0:0:0:1 or ::1)
Identify a loopback interface
IPv4-compatible address (0:0:0:0:0:0:w.c.x.z or ::w.c.x.z)
Used by dual-stack nodes
IPv6 traffic is automatically encapsulated with an IPv4 header and send to the destination using the IPv4 infrastructure
IPv4 mapped address (0:0:0:0:0:FFFF:w.c.x.z or ::FFFF:w.c.x.z)
Represent an IPv4-only node to an IPv6 node
Only use a single listening socket to handle connections from client via both IPv6 and IPv4 protocols.
Never used as a source or destination address of IPv6 packet
Rarely implemented

29. IPv6 Header Format

30. Address Autoconfiguration (1)
Allow plug and play
BOOTP and DHCP are used in IPv4
DHCPng will be used with IPv6
Two Methods: Stateless and Stateful
Stateless:
A system uses link-local address as source and multicasts to "All routers on this link" (Router discovery protocol)
Router replies and provides all the needed prefix info
All prefixes have a associated lifetime
System can use link-local address permanently if no router

31. Address Autoconfiguration (2)
Stateful:
Problem w/ stateless: Anyone can connect
Routers ask the new system to go DHCP server (by setting managed configuration bit)
System multicasts to "All DHCP servers"
DHCP server assigns an address

32. Neighbor Discovery (ND)
Node (Hosts and Routers) use ND to determinate the link-layer addresses for neighbors known to reside on attached links and quick purge cached valued that become invalid
Hosts also use ND to find neighboring router that willing to forward packets on their behalf
Nodes use the protocol to actively keep track of which neighbors are reachable and which are not, and to detect changed link-layer addresses
Replace ARP, ICMP Router Discovery, and ICMP Redirect used in IPv4

33. IPv6 ND Mechanisms (1) Router discovery Prefix discovery
Equivalent to ICMPv4 Router Discovery
Prefix discovery
Equivalent to ICMPv4 Address Mask Request/Reply
Parameter discovery
Discovery additional parameter (ex. link MTU, default hop limit for outgoing packet)
Address auto-configuration
Configure IP address for interfaces
Address resolution: Equivalent to ARP in IPv4

34. IPv6 ND Mechanisms (2) Next-hop determination
Destination address, or
Address of an on-link default router
Neighbor unreachable detection (NUD)
Duplicate address detection (DAD)
Determine that an address considered for use is not already in use by a neighboring node
First-hop Redirect function
Inform a host of a better first-hop IPv6 address to reach a destination,
Equivalent to ICMPv4 Redirect

35. IPv6 References RFC 2460: IPv6 RFC 2461: Neighbor Discovery
RFC 2462: Stateless Address Autoconfiguration
RFC 3513: Addressing Architecture
RFC 3679: Flow Label Specification
RFC 4443: ICMPv6
RFC 3810: Multicast Listener Discovery (MLDv2)