1. Implementing IP Addressing Services
Accessing the WAN – Chapter 7

2. Objectives Configure DHCP in an enterprise branch network
Configure NAT on a Cisco router
Configure new generation RIP (RIPng) to use IPv6

3. Configure DHCP in an Enterprise Branch Network
Describe the function of DHCP in a network
Graphic

4. Configure DHCP in an Enterprise Branch Network
Describe how DHCP dynamically assigns an IP address to a client
Graphic

5. DHCP Discover
Source IP

6. DHCP Offer
UPD Port 68 = BootP Server

7. DHCP Request
After the client receives a DHCPOFFER, it responds with a DHCPREQUEST message, indicating its intent to accept the parameters in the DHCPOFFER, and moves into the Requesting state.
The client chooses one DHCPOFFER and responds to that DHCP server only, implicitly declining all other DHCPOFFER messages.
The client identifies the selected server by populating the Server Identifier option field with the DHCP server's IP address.
The DHCPREQUEST is also a broadcast, so all DHCP servers that sent a DHCPOFFER will see the DHCPREQUEST, and each will know whether its DHCPOFFER was accepted or declined.
Even though the client has been offered an IP address, it will send the DHCPREQUEST message with a source IP address of At this time, the client has not yet received verification that it is clear to use the IP address.

8. DHCPACK
The DHCPACK message has a source IP address of the DHCP server, and the destination address is once again a broadcast and contains all the parameters that the client requested in the DHCPREQUEST message.
When the client receives the DHCPACK, it enters into the Bound state, and is now free to use the IP address to communicate on the network.
DHCP server stores the lease in its database and uniquely identifies it using the client identifier or chaddr, and the associated IP address.
Both the client and server will use this combination of identifiers to refer to the lease. The client identifier is the Mac address of the device plus the media type.
Before the DHCP client begins using the new address, the DHCP client must calculate the time parameters associated with a leased address, which are Lease Time (LT), Renewal Time (T1), and Rebind Time (T2). The typical default LT is 72 hours.

9. Configure DHCP Step 1
Define a range of addresses that are not to be allocated.
These are usually static addresses reserved for the router interface, switch management IP address, servers, and local network printers.
Graphic

10. DHCP Step 2: Pool

11. DHCP Step 3: Specific Tasks

12. DHCP Sample Configuration

13. show ip dhcp pool

14. Show ip dhcp binding

15. Show ip dhcp server statistics

16. Configure DHCP in an Enterprise Branch Network
Describe how to configure a Cisco router as a DHCP client
Graphic

17. Configuring a DHCP Client

18. DHCP Relay

19. Relay Configuration

20. Configure DHCP in an Enterprise Branch Network
Describe how to troubleshoot a DHCP configuration
Graphic

21. DHCP Configuration with SDM

22. Add DHCP Pool

23. DHCP Pools

24. Troubleshooting Address Conflict
R2# show ip dhcp conflict IP address Detection Method Detection time Ping Feb :28 PM Gratuitous ARP Feb :12 AM The show ip dhcp conflict command displays all address conflicts recorded by the DHCP server. The server uses the ping command to detect conflicts. The client uses Address Resolution Protocol (ARP) to detect clients. If an address conflict is detected, the address is removed from the pool and not assigned until an administrator resolves the conflict.

25. Debug IP Packet

26. Configure NAT on a Cisco Router
Describe the operation and benefits of using private and public IP addressing
Graphic

27. Network Address Translation - NAT

28. What is NAT?
NAT translates non-routable, private, internal addresses into routable, public addresses.
NAT has an added benefit of adding a degree of privacy and security to a network because it hides internal IP addresses from outside networks.
A NAT-enabled device typically operates at the border of a stub network.
A stub network is a network that has a single connection to its neighbor network.

29. NAT Terminology

30. NAT Terminology Explained
Inside local address - Usually not an IP address assigned by a service provider and is most likely an RFC 1918 private address. In the figure (previous slide), the IP address is assigned to the host PC1 on the inside network.
Inside global address - Valid public address that the inside host is given when it exits the NAT router. When traffic from PC1 is destined for the web server at , router R2 must translate the address. In this case, IP address is used as the inside global address for PC1.
Outside global address - Reachable IP address assigned to a host on the Internet. For example, the web server is reachable at IP address
Outside local Address: An address of an external device as it is referred to by devices on the local network. In some situations, this may be identical to the outside global address of that outside device.

31. Configure NAT on a Cisco Router
Explain the advantages and disadvantages of NAT
Graphic

32. NAT Types
Dynamic NAT uses a pool of public addresses and assigns them on a first-come, first-served basis. When a host with a private IP address requests access to the Internet, dynamic NAT chooses an IP address from the pool that is not already in use by another host. This is the mapping described so far.
Static NAT uses a one-to-one mapping of local and global addresses, and these mappings remain constant. Static NAT is particularly useful for web servers or hosts that must have a consistent address that is accessible from the Internet. These internal hosts may be enterprise servers or networking devices.

33. NAT Overload

34. Configure NAT on a Cisco Router
Describe how to configure static NAT to conserve IP address space in a network
Graphic

35. Configuring Static NAT

36. Configure NAT on a Cisco Router
Describe how to configure dynamic NAT to conserve IP address space in a network
Graphic

37. Dynamic NAT

38. Configuring Dynamic NAT

39. IP NAT Overload

40. IP NAT Overload with Address Pool

41. Port Forwarding
Port forwarding (sometimes referred to as tunneling) is the act of forwarding a network port from one network node to another.
This technique can allow an external user to reach a port on a private IP address (inside a LAN) from the outside through a NAT-enabled router.
Port forwarding allows users on the Internet to access internal servers by using the WAN port address and the matched external port number.
When users send these types of requests to your WAN port IP address via the Internet, the router forwards those requests to the appropriate servers on your LAN.
For security reasons, broadband routers do not by default permit any external network request to be forwarded to an inside host.

42. Configure NAT on a Cisco Router
Describe how to configure port forwarding
Graphic

43. Configure NAT on a Cisco Router
Describe how to verify and troubleshoot NAT and NAT overload configurations
Graphic &

48. Debug IP NAT

49. Configure New Generation RIP (RIPng) to use IPv6
Explain the need for IPv6 to provide a long-term solution to the depletion problem of IP address
Graphic (why IPv6)

50. Shrinking IP Address Space

51. Larger Address Space

52. IPv6 Structure

53. IPv4 and IPv6 Address Space

54. Headers
More next slide
Simpler format
Fewer Fields

55. Flow Label
This field was created to provide additional support for real-time datagram delivery and quality of service features.
The concept of a flow is defined in RFC 2460 as a sequence of datagrams sent from a source device to one or more destination devices.
A unique flow label is used to identify all the datagrams in a particular flow, so that routers between the source and destination all handle them the same way, to help ensure uniformity in how the datagrams in the flow are delivered.
For example, if a video stream is being sent across an IP internetwork, the datagrams containing the stream could be identified with a flow label to ensure that they are delivered with minimal latency.
NOTE: Not all devices and routers may support flow label handling, and use of the field by a source device is entirely optional. Also, the field is still somewhat experimental and may be refined over time.
Source:

56. IPv6 Representation The following is an IPv6 address in binary form:
The 128-bit address is divided along 16-bit boundaries, as follows:

57. IPv6 Representation – Part 2
Each 16-bit block is converted to hexadecimal and delimited with colons. The result is:
21DA:00D3:0000:2F3B:02AA:00FF:FE28:9C5A
IPv6 representation can be further simplified by removing the leading zeros within each 16-bit block. However, each block must have at least a single digit. With leading zero suppression, the address representation becomes:
21DA:D3:0:2F3B:2AA:FF:FE28:9C5A

58. IPv6 Compressing Zeros

59. IPv6 Address Structure

60. IPv4/IPv6 Embedding
The embedding address space is part of the reserved address block whose addresses begin with eight zero bits
Used for migration and tunneling

61. Configure New Generation RIP (RIPng) to use IPv6
Explain the various methods of assigning IPv6 addresses to a device
Graphic
EUI: Extended Universal Identifier

62. Configure New Generation RIP (RIPng) to use IPv6
Describe the transition strategies for implementing IPv6
Graphic
Network Address Translation - Protocol Translation

63. Dual Stacking
Dual stacking is an integration method in which a node has implementation and connectivity to both an IPv4 and IPv6 network.
This is the recommended option and involves running IPv4 and IPv6 at the same time.
Routers are configured to support both protocols, with IPv6 being the preferred protocol.

64. Tunneling
Manual IPv6-over-IPv4 tunneling - An IPv6 packet is encapsulated within the IPv4 protocol. This method requires dual-stack routers.
Dynamic 6to4 tunneling - Automatically establishes the connection of IPv6 islands through an IPv4 network, typically the Internet.
It dynamically applies a valid, unique IPv6 prefix to each IPv6 island, which enables the fast deployment of IPv6 in a corporate network without address retrieval from the ISPs or registries.

65. Cisco IOS Dual Stack

66. IPv6 Tunneling

67. RIPng Routing Protocol
Also referred to as: IPng RIP

68. Enabling IPv6

69. Extended Universal Identifier - EUI
More Info:

71. Configuring RIPng for IPv6
To enable RIPng routing on the router, use the <ipv6 router rip name>global configuration command. The name parameter identifies the RIP process. This process name is used later when configuring RIPng on participating interfaces.
For RIPng, instead of using the network command to identify which interfaces should run RIPng, you use the command <ipv6 rip name enable> in interface configuration mode to enable RIPng on an interface. The name parameter must match the name parameter in <the ipv6 router rip> command.
Enabling RIP on an interface dynamically creates a "router rip" process if necessary.

72. Enabling RIPng

73. Customizing - Optional
Source:

75. Verifying RIPng IPv6

76. Troubleshooting

77. Summary Dynamic Host Control Protocol (DHCP) DHCP operation
This is a means of assigning IP address and other configuration information automatically.
DHCP operation
3 different allocation methods
Manual
Automatic
Dynamic
Steps to configure DHCP
Define range of addresses
Create DHCP pool
Configure DHCP pool specifics

78. Summary DHCP Relay Troubleshooting DHCP
Concept of using a router configured to listen for DHCP messages from DHCP clients and then forwards those messages to servers on different subnets
Troubleshooting DHCP
Most problems arise due to configuration errors
Commands to aid troubleshooting
Show ip dhcp
Show run
debug

79. Summary Private IP addresses Network Address Translation (NAT)
Class A = 10.x.x.x
Class B = x.x – x.x
Class C = x.x
Network Address Translation (NAT)
A means of translating private IP addresses to public IP addresses
Type s of NAT
Static
Dynamic
Some commands used for troubleshooting
Show ip nat translations
Show ip nat statistics
Debug ip nat

80. Summary IPv6 Cisco IOS Dual Stack IPv6 Tunneling
A 128 bit address that uses colons to separate entries
Normally written as 8 groups of 4 hexadecimal digits
Cisco IOS Dual Stack
A way of permitting a node to have connectivity to an IPv4 & IP v6 network simultaneously
IPv6 Tunneling
An IPV6 packet is encapsulated within another protocol

81. Summary Configuring RIPng with IPv6 1st globally enable IPv6
2nd enable IPv6 on interfaces on which IPv6 is to be enabled
3rd enable RIPng using either
ipv6 rotuer rip name
ipv6 router name enable