¡GoConqr estrena diseño! Cuéntanos qué te parece.

Regístrate gratis

Fichas

E2_10 DHCP

John Dedios CCNA CCNA Español 63 fichas

DHCPv4 Operation - Lease Origination Ej: a client starts the process with a broadcast DHCPDISCOVER message with its own MAC…

Fichas del conjunto (63)

  1. 1Introducing DHCPv4 A dedicated DHCPv4 server is scalable and relatively easy to manage. However, in a small branch or SOHO location, a Cisco router can be configured to provide DHCPv4 services without the need for a dedicated server. A Cisco IOS feature set (called ”Easy IP”) offers an optional, full-featured DHCPv4 server. DHCPv4 includes three different address allocation mechanisms to provide flexibility when assigning IP addresses:1. Manual Allocation - The administrator assigns a pre-allocated IPv4 address to the client, and DHCPv4 communicates only the IPv4 address to the device.
    2. Automatic Allocation - DHCPv4 automatically assigns a static IPv4 address permanently to a device, selecting it from a pool of available addresses. There is no lease and the address is permanently assigned to the device.
    3. Dynamic Allocation - DHCPv4 dynamically assigns, or leases, an IPv4 address from a pool of addresses for a limited period of time chosen by the server, or until the client no longer needs the address.
  2. 2DHCPv4 Operation - Lease Origination Ej: a client starts the process with a broadcast DHCPDISCOVER message with its own MAC address to discover available DHCPv4 servers. 1. The DHCPDISCOVER message finds DHCPv4 servers on the network. Because the client has no valid IPv4 information at bootup, it uses Layer 2 and Layer 3 broadcast addresses to communicate with the server.DHCPv4 Operation - Lease Origination Ej: a client starts the process with a broadcast DHCPDISCOVER message with its own MAC address to di...
  3. 3DHCPv4 Operation - DHCP Offer (DHCPOFFER) 2. When the DHCPv4 server receives a DHCPDISCOVER message, it reserves an available IPv4 address to lease to the client. The server also creates an ARP entry consisting of the MAC address of the requesting client and the leased IPv4 address of the client. The DHCPv4 server sends the binding DHCPOFFER message to the requesting client.DHCPv4 Operation - DHCP Offer (DHCPOFFER) 2. When the DHCPv4 server receives a DHCPDISCOVER message, it reserves an available IPv4 addres...
  4. 4DHCPv4 Operation - DHCP Request (DHCPREQUEST) 3. When the client receives the DHCPOFFER from the server, it sends back a DHCPREQUEST message This message is used for both lease origination and lease renewal. When used for lease origination, the DHCPREQUEST serves as a binding acceptance notice to the selected server for the parameters it has offered and an implicit decline to any other servers that may have provided the client a binding offer.DHCPv4 Operation - DHCP Request (DHCPREQUEST) 3. When the client receives the DHCPOFFER from the server, it sends back a DHCPREQUEST mess...
  5. 5DHCPv4 Operation - DHCP Acknowledgment (DHCPACK) 4. On receiving the DHCPREQUEST message, the server verifies the lease information with an ICMP ping to that address to ensure it is not being used already, creates a new ARP entry for the client lease, and replies with a unicast DHCPACK message The DHCPACK message is a duplicate of the DHCPOFFER, except for a change in the message type field. When the client receives the DHCPACK message, it logs the configuration information and performs an ARP lookup for the assigned address. If there is no reply to the ARP, the client knows that the IPv4 address is valid and starts using it as its own. .DHCPv4 Operation - DHCP Acknowledgment (DHCPACK) 4. On receiving the DHCPREQUEST message, the server verifies the lease information with ...
  6. 6DHCPv4 Operation - Lease Renewal 5.1. DHCP Request (DHCPREQUEST) When the lease has expired, the client sends a DHCPREQUEST message directly to the DHCPv4 server that originally offered the IPv4 address. If a DHCPACK is not received within a specified amount of time, the client broadcasts another DHCPREQUEST so that one of the other DHCPv4 servers can extend the lease. 5.2. DHCP Acknowledgment (DHCPACK) On receiving the DHCPREQUEST message, the server verifies the lease information by returning a DHCPACKDHCPv4 Operation - Lease Renewal 5.1. DHCP Request (DHCPREQUEST) When the lease has expired, the client sends a DHCPREQUEST message direc...
  7. 7DHCPv4 Message Format DHCPv4 messages sent from the client use UDP source port 68 and destination port 67. DHCPv4 messages sent from the server to the client use UDP source port 67 and destination port 68. * Operation (OP) Code - Specifies the general type of message. A value of 1 indicates a request message; a value of 2 is a reply message. * Hardware Type - Identifies the type of hardware used in the network. For example, 1 is Ethernet, 15 is Frame Relay, and 20 is a serial line. These are the same codes used in ARP messagesDHCPv4 Message Format DHCPv4 messages sent from the client use UDP source port 68 and destination port 67. DHCPv4 messages sent from the ...
  8. 8DHCPv4 Message Format * Hardware Address Length - Specifies the length of the address. * Hops - Controls the forwarding of messages. Set to 0 by a client before transmitting a request. * Transaction Identifier - Used by the client to match the request with replies received from DHCPv4 servers. * Seconds - Identifies the number of seconds elapsed since a client began attempting to acquire or renew a lease. Used by DHCPv4 servers to prioritize replies when multiple client requests are outstanding.DHCPv4 Message Format * Hardware Address Length - Specifies the length of the address. * Hops - Controls the forwarding of messages. Set ...
  9. 9DHCPv4 Message Format * Flags - Used by a client that does not know its IPv4 address when it sends a request. Only one of the 16 bits is used, which is the broadcast flag. A value of 1 in this field tells the DHCPv4 server or relay agent receiving the request that the reply should be sent as a broadcast. * Client IP Address - Used by a client during lease renewal when the address of the client is valid and usable, not during the process of acquiring an address. The client puts its own IPv4 address in this field if and only if it has a valid IPv4 address while in the bound state; otherwise, it sets the field to 0. * Your IP Address - Used by the server to assign an IPv4 address to the client.DHCPv4 Message Format * Flags - Used by a client that does not know its IPv4 address when it sends a request. Only one of the 16 bits is ...
  10. 10DHCPv4 Message Format * Server IP Address - Used by the server to identify the address of the server that the client should use for the next step in the bootstrap process, which may or may not be the server sending this reply. The sending server always includes its own IPv4 address in a special field called the Server Identifier DHCPv4 option. * Gateway IP Address - Routes DHCPv4 messages when DHCPv4 relay agents are involved. The gateway address facilitates communications of DHCPv4 requests and replies between the client and a server that are on different subnets or networks. * Client Hardware Address - Specifies the physical layer of the client.DHCPv4 Message Format * Server IP Address - Used by the server to identify the address of the server that the client should use for the n...
  11. 11DHCPv4 Message Format * Server Name - Used by the server sending a DHCPOFFER or DHCPACK message. The server may optionally put its name in this field. This can be a simple text nickname or a DNS domain name, such as dhcpserver.netacad.net. * Boot Filename - Optionally used by a client to request a particular type of boot file in a DHCPDISCOVER message. Used by a server in a DHCPOFFER to fully specify a boot file directory and filename. * DHCP Options - Holds DHCP options, including several parameters required for basic DHCP operation. This field is variable in length. Both client and server may use this field.DHCPv4 Message Format * Server Name - Used by the server sending a DHCPOFFER or DHCPACK message. The server may optionally put its name i...
  12. 12DHCPv4 Discover Message Because the client has no way of knowing the subnet to which it belongs, the DHCPDISCOVER message is an IPv4 broadcast (destination IPv4 address of 255.255.255.255). The client does not have a configured IPv4 address yet, so the source IPv4 address of 0.0.0.0 is used. Ej: the client IPv4 address (CIADDR), default gateway address (GIADDR), and subnet mask are all marked to indicate that the address 0.0.0.0 is used. Note: Unknown information is sent as 0.0.0.0.DHCPv4 Discover Message Because the client has no way of knowing the subnet to which it belongs, the DHCPDISCOVER message is an IPv4 broa...
  13. 13DHCPv4 Offer Message This message contains initial configuration information for the client, including the IPv4 address that the server offers, the subnet mask, the lease duration, and the IPv4 address of the DHCPv4 server making the offer. The DHCPOFFER message can be configured to include other information, such as the lease renewal time and DNS address.DHCPv4 Offer Message This message contains initial configuration information for the client, including the IPv4 address that the server o...
  14. 14Configuring a Basic DHCPv4 Server Step 1. Excluding IPv4 Addresses - Typically, some IPv4 addresses in a pool are assigned to network devices that require static address assignments. Therefore, these IPv4 addresses should not be assigned to other devices.A single address or a range of addresses can be excluded by specifying the low-address and high-address of the range. Excluded addresses should include the addresses assigned to routers, servers, printers, and other devices that have been manually configuredConfiguring a Basic DHCPv4 Server Step 1. Excluding IPv4 Addresses - Typically, some IPv4 addresses in a pool are assigned to network dev...
  15. 15Configuring a Basic DHCPv4 Server Step 2. Configuring a DHCPv4 Pool Configuring a DHCPv4 server involves defining a pool of addresses to assign. As shown in Figure 3, the ip dhcp pool pool-name command creates a pool with the specified name and puts the router in DHCPv4 configuration mode, which is identified by this prompt Router(dhcp-config)#.Configuring a Basic DHCPv4 Server Step 2. Configuring a DHCPv4 Pool Configuring a DHCPv4 server involves defining a pool of addresses to ...
  16. 16Configuring a Basic DHCPv4 Server Step 3. Configuring Specific Tasks Use the default-router command to define the default gateway router. Typically, the gateway is the LAN interface of the router closest to the client devices. One gateway is required, but you can list up to eight addresses if there are multiple gatewaysConfiguring a Basic DHCPv4 Server Step 3. Configuring Specific Tasks Use the default-router command to define the default gateway router....
  17. 17Configuring a Basic DHCPv4 Server Disabling DHCPv4 The DHCPv4 service is enabled, by default, on versions of Cisco IOS software that support it. To disable the service, use the no service dhcp global configuration mode command. Use the service dhcp global configuration mode command toConfiguring a Basic DHCPv4 Server Disabling DHCPv4 The DHCPv4 service is enabled, by default, on versions of Cisco IOS software that supp...
  18. 18Verifying DHCPv4 Ej: the show running-config | section dhcp command output displays the DHCPv4 commands configured on R1. The | section parameter displays only the commands associated with DHCPv4 configuration.Verifying DHCPv4 Ej: the show running-config | section dhcp command output displays the DHCPv4 commands configured on R1. The | section p...
  19. 19Verifying DHCPv4 Ej: the operation of DHCPv4 can be verified using the "show ip dhcp binding" command. This command displays a list of all IPv4 address to MAC address bindings that have been provided by the DHCPv4 " show ip dhcp server statistics"Verifying DHCPv4 Ej: the operation of DHCPv4 can be verified using the "show ip dhcp binding" command. This command displays a list of al...
  20. 20DHCPv4 Relay Ej: PC1 is attempting to renew its IPv4 address. To do so, the "ipconfig /release" command is issued. Notice that the IPv4 address is released and the address is shown to be 0.0.0.0. Next, the "ipconfig /renew" command is issued. This command causes PC1 to broadcast a DHCPDISCOVER message. The output shows that PC1 is unable to locate the DHCPv4 server. Because routers do not forward broadcasts, the request is not successful.DHCPv4 Relay Ej: PC1 is attempting to renew its IPv4 address. To do so, the "ipconfig /release" command is issued. Notice that the IPv4 a...
  21. 21—
  22. 22DHCPv4 Relay Ej: A better solution is to configure a Cisco IOS helper address. This solution enables a router to forward DHCPv4 broadcasts to the DHCPv4 server. When a router forwards address assignment/parameter requests, it is acting as a DHCPv4 relay agent. When R1 has been configured as a DHCPv4 relay agent, it accepts broadcast requests for the DHCPv4 service and then forwards those requests as a unicast to the IPv4 address 192.168.11.6.DHCPv4 Relay Ej: A better solution is to configure a Cisco IOS helper address. This solution enables a router to forward DHCPv4 broadcast...
  23. 23DHCPv4 Relay DHCPv4 is not the only service that the router can be configured to relay. By default, the ip helper-address command forwards the following eight UDP services: Port 37: Time Port 49: TACACS Port 53: DNSPort 67: DHCP/BOOTP client
    Port 68: DHCP/BOOTP server
    Port 69: TFTP
    Port 137: NetBIOS name service
    Port 138: NetBIOS datagram service
  24. 24Configuring a Router as DHCPv4 Client Ej: assume that an ISP has been configured to provide select customers with IP addresses from the 209.165.201.0/27 network range. After the G0/1 interface is configured with the: "ip address dhcp" command, the "show ip interface g0/1" command confirms that the interface is up and that the address was allocated by a DHCPv4 server.Configuring a Router as DHCPv4 Client Ej: assume that an ISP has been configured to provide select customers with IP addresses from the 2...
  25. 25Configuración de un router SOHO como cliente DHCPv4 Nota: la característica de clonación de la dirección MAC utiliza una dirección especificada como la dirección MAC de origen en el ISP que interactúa con la interfaz del router. Muchos ISP asignan direcciones IPv4 sobre la base de la dirección MAC del dispositivo durante la instalación inicial. Cuando otro dispositivo, como un router SOHO, está conectado al ISP, el ISP puede requerir que se configure la dirección MAC del dispositivo original en la interfaz WAN.Configuración de un router SOHO como cliente DHCPv4 Nota: la característica de clonación de la dirección MAC utiliza una dirección especi...
  26. 26Troubleshooting Tasks DHCP Troubleshooting Task 1: Resolve IPv4 Address Conflicts When the client reboots, it requests an IPv4 address. If the DHCPv4 server does not respond quickly, the client uses the last IPv4 address. The situation then arises where two clients are using the same IPv4 address, creating a conflict. The "show ip dhcp conflict" command displays all address conflicts recorded by the DHCPv4 server. The server uses the "ping" command to detect clients. The client uses Address Resolution Protocol "(ARP)" to detect conflicts.If an address conflict is detected, the address is removed from the pool and not assigned until an administrator resolves the conflict.
    This output displays IP addresses that have conflicts with the DHCP server. It shows the detection method and detection time for conflicting IP addresses that the DHCP server has offered.
    ( R1# show ip dhcp conflict
    IP address Detection Method Detection time
    192.168.10.32 Ping Feb 16 2013 12:28 PM
    192.168.10.64 Gratuitous ARP Feb 23 2013 08:12 AM )
  27. 27Troubleshooting Tasks DHCP Troubleshooting Task 2: Verify Physical Connectivity First, use the "show interfaces (interface)" command to confirm that the router interface acting as the default gateway for the client is operational. If the state of the interface is anything other than up, the port does not pass traffic, including DHCP client requests.Troubleshooting Task 3: Test Connectivity using a Static IP Address
    When troubleshooting any DHCPv4 issue, verify network connectivity by configuring static IPv4 address information on a client workstation. If the workstation is unable to reach network resources with a statically configured IPv4 address, the root cause of the problem is not DHCPv4.
    At this point, network connectivity troubleshooting is required.
  28. 28Troubleshooting Tasks DHCP Troubleshooting Task 4: Verify Switch Port Configuration If the DHCPv4 client is unable to obtain an IPv4 address from the DHCPv4 server on startup, attempt to obtain an IPv4 address from the DHCPv4 server by manually forcing the client to send a DHCPv4 request.Note: If there is a switch between the client and the DHCPv4 server, and the client is unable to obtain the DHCP configuration, switch port configuration issues may be the cause.
    ** These causes may include issues from trunking and channeling, STP, and RSTP. PortFast configuration and edge port configurations resolve the most common DHCPv4 client issues that occur with an initial installation of a Cisco switch.
  29. 29Troubleshooting Tasks DHCP Troubleshooting Task 5: Test DHCPv4 Operation on the Same Subnet or VLAN It is important to distinguish whether DHCPv4 is functioning correctly when the client is on the same subnet or VLAN as the DHCPv4 server. If DHCPv4 is working correctly when the client is on the same subnet or VLAN, the problem may be the DHCP relay agent. If the problem persists even with testing DHCPv4 on the same subnet or VLAN as the DHCPv4 server, the problem may actually be with the DHCPv4 serverTroubleshooting Tasks DHCP Troubleshooting Task 5: Test DHCPv4 Operation on the Same Subnet or VLAN It is important to distinguish whethe...
  30. 30Verify Router DHCPv4 Configuration * Step 1. Verify that the "ip helper-address" command is configured on the correct interface. It must be present on the inbound interface of the LAN containing the DHCPv4 client workstations and must be directed to the correct DHCPv4 server The "show ip interface" command can also be used to verify the DHCPv4 relay on an interface. * Step 2. Verify that the global configuration command "no service dhcp" has not been configured.Verify Router DHCPv4 Configuration * Step 1. Verify that the "ip helper-address" command is configured on the correct interface. It must ...
  31. 31Debugging DHCPv4 On routers configured as DHCPv4 servers, the DHCPv4 process fails if the router is not receiving requests from the client. As a troubleshooting task, verify that the router is receiving the DHCPv4 request from the client. This troubleshooting step involves configuring an ACL for debugging output. Ej: an extended ACL permitting only packets with UDP destination ports of 67 or 68. These are the typical ports used by DHCPv4 clients and servers when sending DHCPv4 messages This output only shows a summary of the packet and not the DHCPv4 message itself. Nevertheless, the router did receive a broadcast packet with the source and destination IP and UDP ports that are correct for DHCPv4.Debugging DHCPv4 On routers configured as DHCPv4 servers, the DHCPv4 process fails if the router is not receiving requests from the clien...
  32. 32Debugging DHCPv4 Another useful command for troubleshooting DHCPv4 operation is the: "debug ip dhcp server events" command. This command reports server events, like address assignments and database updates. It is also used for decoding DHCPv4 receptions and transmissions.Debugging DHCPv4 Another useful command for troubleshooting DHCPv4 operation is the: "debug ip dhcp server events" command. This command ...
  33. 33Stateless Address Autoconfiguration (SLAAC) there are two methods in which IPv6 global unicast addresses can be assigned dynamically: Ej: Stateless Address Autoconfiguration (SLAAC), as shown in the figure Dynamic Host Configuration Protocol for IPv6 (Stateful DHCPv6)Stateless Address Autoconfiguration (SLAAC) there are two methods in which IPv6 global unicast addresses can be assigned dynamically: Ej:...
  34. 34Stateless Address Autoconfiguration (SLAAC) SLAAC is a method in which a device can obtain an IPv6 global unicast address without the services of a DHCPv6 server. At the core of SLAAC is ICMPv6. ICMPv6 is similar to ICMPv4 but includes additional functionality and is a much more robust protocol. SLAAC uses ICMPv6 Router Solicitation and Router Advertisement messages to provide addressing and other configuration information that would normally be provided by a DHCP serverSLAAC is stateless. A stateless service means there is no server that maintains network address information.
    Unlike DHCP, there is no SLAAC server that knows which IPv6 addresses are being used and which ones are available.
  35. 35Stateless Address Autoconfiguration (SLAAC) * Router Solicitation (RS) message - When a client is configured to obtain its addressing information automatically using SLAAC, the client sends an RS message to the router. The RS message is sent to the "IPv6 all-routers multicast address FF02::2." * Router Advertisement (RA) message - RA messages are sent by routers to provide addressing information to clients configured to obtain their IPv6 addresses automaticallyThe RA message includes the prefix and prefix length of the local segment. A client uses this information to create its own IPv6 global unicast address.
    A router sends an RA message periodically, or in response to an RS message.
    By default, Cisco routers send RA messages every 200 seconds. RA messages are always sent to the "IPv6 all-nodes multicast address FF02::1."
  36. 36SLAAC Operation Step 3 - PC1 receives the RA message containing the prefix and prefix length for the local network. PC1 will use this information to create its own IPv6 global unicast address. PC1 now has a 64-bit network prefix, but needs a 64-bit Interface ID (IID) to create a global unicast address. There are two ways PC1 can create its own unique IID: * EUI-64 - Using the EUI-64 process, PC1 will create an IID using its 48-bit MAC address. * Randomly generated - The 64-bit IID can be a random number generated by the client operating system.SLAAC Operation Step 3 - PC1 receives the RA message containing the prefix and prefix length for the local network. PC1 will use this inf...
  37. 37SLAAC Operation Step 4 - Because SLAAC is a stateless process, before PC1 can use this newly created IPv6 address it must verify that it is unique. PC1 sends an ICMPv6 Neighbor Solicitation message with its own address as the target IPv6 address.If no other devices respond with a Neighbor Advertisement message, then the address is unique and can be used by PC1. If a Neighbor Advertisement is received by PC1 then the address is not unique and the operating system has to determine a new Interface ID to use.
    This process is part of ICMPv6 Neighbor Discovery and is known as Duplicate Address Detection (DAD).
  38. 38SLAAC and DHCPv6 The decision of whether a client is configured to obtain its IPv6 address information automatically using SLAAC, DHCPv6, or a combination of both depends on the settings within the RA message. The two flags are the Managed Address Configuration flag (M flag) and the Other Configuration flag (O flag). Note: Although the RA message specifies the process the client should use in obtaining an IPv6 address dynamically, the client operating system may choose to ignore the RA message and use the services of a DHCPv6 server exclusively.SLAAC and DHCPv6 The decision of whether a client is configured to obtain its IPv6 address information automatically using SLAAC, DHCPv6,...
  39. 39SLAAC Option (Router Advertisement only) RA message exclusively includes: prefix, prefix-length, DNS server, MTU, and default gateway information. RA messages are configured on an individual interface of a router. To re-enable an interface for SLAAC that might have been set to another option, the M and O flags need to be reset to their initial values of 0. This is done using the following interface configuration mode commands: Router(config-if)# no ipv6 nd managed-config-flag Router(config-if)# no ipv6 nd other-config-flagSLAAC Option (Router Advertisement only) RA message exclusively includes: prefix, prefix-length, DNS server, MTU, and default gateway inf...
  40. 40Stateless DHCPv6 Option (Router Advertisement and DHCPv6) The client will then communicate with a stateless DHCPv6 server to obtain additional information not provided in the RA message. This may be a list of DNS server IPv6 addresses, for example. This process is known as stateless DHCPv6 because the server is not maintaining any client state information (i.e., a list of available and allocated IPv6 addresses). The stateless DHCPv6 server is only providing configuration parameters for clients, not IPv6 addresses. To modify the RA message sent on the interface of a router to indicate stateless DHCPv6, use the following command: Router(config-if)# ipv6 nd other-config-flagStateless DHCPv6 Option (Router Advertisement and DHCPv6) The client will then communicate with a stateless DHCPv6 server to obtain addit...
  41. 41Stateful DHCPv6 (DHCPv6 only) This option is the most similar to DHCPv4. In this case, the RA message informs the client not to use the information in the RA message. All addressing information and configuration information must be obtained from a stateful DHCPv6 serve The M flag indicates whether or not to use stateful DHCPv6. The O flag is not involved. The following command is used to change the M flag from 0 to 1 to signify stateful DHCPv6: Router(config-if)# ipv6 nd managed-config-flagStateful DHCPv6 (DHCPv6 only) This option is the most similar to DHCPv4. In this case, the RA message informs the client not to use the i...
  42. 42DHCPv6 Operations Stateless or stateful DHCPv6, or both begin with an ICMPv6 RA message from the router. ** DHCPv6 messages are sent over UDP. DHCPv6 messages from the server to the client use UDP destination port 546. The client sends DHCPv6 messages to the server using UDDHCPv6 Operations Stateless or stateful DHCPv6, or both begin with an ICMPv6 RA message from the router. ** DHCPv6 messages are sent over...
  43. 43DHCPv6 Operations 3. The client, now a DHCPv6 client, needs to locate a DHCPv6 server. The client sends a DHCPv6 SOLICIT message to the reserved IPv6 multicast all-DHCPv6-servers address "FF02::1:2" This multicast address has link-local scope, which means routers do not forward the messages to other networks. 4. One or more DHCPv6 servers respond with a DHCPv6 ADVERTISE message. The ADVERTISE message informs the DHCPv6 client that the server is available for DHCPv6 service.DHCPv6 Operations 3. The client, now a DHCPv6 client, needs to locate a DHCPv6 server. The client sends a DHCPv6 SOLICIT message to the r...
  44. 44DHCPv6 Operations 5. Stateless DHCPv6 client - The client sends a DHCPv6 INFORMATION-REQUEST message to the DHCPv6 server requesting only configuration parameters, such as DNS server address. The client generated its own IPv6 address using the prefix from the RA message and a self-generated Interface ID. 5. Stateful DHCPv6 client - The client sends a DHCPv6 REQUEST message to the server to obtain an IPv6 address and all other configuration parameters from the server. 6. The server sends a DHCPv6 REPLY to the client containing the information requested in the REQUEST or INFORMATION-REQUEST messageDHCPv6 Operations 5. Stateless DHCPv6 client - The client sends a DHCPv6 INFORMATION-REQUEST message to the DHCPv6 server requesting only...
  45. 45Configuring a Router as a Stateless DHCPv6 Server Step 1. Enable IPv6 Routing This command is not necessary for the router to be a stateless DHCPv6 server, but is required for sending ICMPv6 RA messages. Step 3. Configure Pool Parameters During the SLAAC process, the client received the information it needed to create an IPv6 global unicast address. The client also received the default gateway information using the source IPv6 address from the RA message, which is the link-local address of the router. However, the stateless DHCPv6 server can be configured to provide other information that might not have been included in the RA message such as DNS server address and the domain nameConfiguring a Router as a Stateless DHCPv6 Server Step 1. Enable IPv6 Routing This command is not necessary for the router to be a statel...
  46. 46Configuring a Router as a Stateless DHCPv6 Server Step 4. Configure the DHCPv6 InterfaceThe O flag needs to be changed from 0 to 1 using the interface command "ipv6 nd other-config-flag". RA messages sent on this interface indicate that additional information is available from a stateless DHCPv6 server.. Ej: Notice that router R3 is shown as a DHCPv6 client. R3 is configured as a client to help verify the stateless DHCPv6 operations.Configuring a Router as a Stateless DHCPv6 Server Step 4. Configure the DHCPv6 InterfaceThe O flag needs to be changed from 0 to 1 using ...
  47. 47Configuring a Router as a Stateless DHCPv6 Client Ej: the ipv6 enable command is used because the router does not yet have a global unicast address. The ipv6 address autoconfig command enables automatic configuration of IPv6 addressing using SLAAC.Configuring a Router as a Stateless DHCPv6 Client Ej: the ipv6 enable command is used because the router does not yet have a global unica...
  48. 48Verifying Stateless DHCPv6 Ej: the show ipv6 dhcp pool command verifies the name of the DHCPv6 pool and its parameters. The number of active clients is 0, because there is no state being maintained by the server.Verifying Stateless DHCPv6 Ej: the show ipv6 dhcp pool command verifies the name of the DHCPv6 pool and its parameters. The number of act...
  49. 49Verifying the Stateless DHCPv6 Client The IPv6 global unicast address was created using SLAAC, which includes the prefix contained in the RA message. The IID was generated using EUI-64. DHCPv6 was not used to assign the IPv6 address. The default router information is also from the RA message. This was the source IPv6 address of the packet that contained the RA message and the link-local address of the router.Verifying the Stateless DHCPv6 Client The IPv6 global unicast address was created using SLAAC, which includes the prefix contained in the...
  50. 50Verifying the Stateless DHCPv6 Client Ej: output from the debug ipv6 dhcp detail command shows the DHCPv6 messages exchanged between the client and the server. In this example, the command has been entered on the client. The INFORMATION-REQUEST message is shown because it is sent from a stateless DHCPv6 client. Notice that the client, router R3, is sending the DHCPv6 messages from its link-local address to the All_DHCPv6_Relay_Agents_and_Servers address "FF02::1:2."Verifying the Stateless DHCPv6 Client Ej: output from the debug ipv6 dhcp detail command shows the DHCPv6 messages exchanged between the ...
  51. 51Configuring a Router as a Stateful DHCPv6 Server Step 3. Configure Pool Parameters With stateful DHCPv6 all addressing and other configuration parameters must be assigned by the DHCPv6 server. The "address prefix" command is used to indicate the pool of addresses to be allocated by the server. The "lifetime" option indicates the valid and preferred lease times in seconds. As with stateless DHCPv6, the client uses the source IPv6 address from the packet that contained the RA message.Configuring a Router as a Stateful DHCPv6 Server Step 3. Configure Pool Parameters With stateful DHCPv6 all addressing and other configur...
  52. 52Configuring a Router as a Stateful DHCPv6 Server Step 4. Interface Commands The M flag needs to be changed from 0 to 1 using the interface command " ipv6 nd managed-config-flag" This informs the device not to use SLAAC but to obtain IPv6 addressing and all configuration parameters from a stateful DHCPv6 server.Configuring a Router as a Stateful DHCPv6 Server Step 4. Interface Commands The M flag needs to be changed from 0 to 1 using the interfac...
  53. 53Configuring a Router as a Stateful DHCPv6 Client Ej: use the "ipv6 enable" interface configuration mode command to allow the router to receive a link-local address to send RS messages and participate in DHCPv6. The "ipv6 address dhcp" interface configuration mode command enables the router to behave as a DHCPv6 client on this interface.Configuring a Router as a Stateful DHCPv6 Client Ej: use the "ipv6 enable" interface configuration mode command to allow the router to re...
  54. 54Verifying Stateful DHCPv6 Ej: the show ipv6 dhcp pool command verifies the name of the DHCPv6 pool and its parameters. The number of active clients is 1, which reflects client R3 receiving its IPv6 global unicast address from this server.Verifying Stateful DHCPv6 Ej: the show ipv6 dhcp pool command verifies the name of the DHCPv6 pool and its parameters. The number of acti...
  55. 55Verifying Stateful DHCPv6 Ej: The "show ipv6 dhcp binding" command, displays the automatic binding between the link-local address of the client and the address assigned by the server. FE80::32F7:DFF:FE25:2DE1 is the link-local address of the client. In this example, this is the G0/1 interface of R3. This address is bound to the IPv6 global unicast address, 2001:DB8:CAFE:1:5844:47B2:2603:C171, which was assigned by R1Verifying Stateful DHCPv6 Ej: The "show ipv6 dhcp binding" command, displays the automatic binding between the link-local address of the ...
  56. 56Verifying the Stateful DHCPv6 Client The output from the "show ipv6 interface" command, verifies the IPv6 global unicast address on DHCPv6 client R3 that was assigned by the DHCPv6 server. The default router information is not from the DHCPv6 server, but was determined by using the source IPv6 address from the RA message. Although the client does not use the information contained in the RA message, it is able to use the source IPv6 address for its default gateway information.Verifying the Stateful DHCPv6 Client The output from the "show ipv6 interface" command, verifies the IPv6 global unicast address on DHCPv...
  57. 57Configuring a Router as a DHCPv6 Relay Agent DHCPv6 messages from clients are sent to the IPv6 multicast address FF02::1:2. All_DHCPv6_Relay_Agents_and_Servers address. This address has link-local scope which means routers do not forward these messages. The router must be configured as a DHCPv6 relay agent to enable the DHCPv6 client and server to communicate. "ipv6 dhcp relay destination"Configuring a Router as a DHCPv6 Relay Agent DHCPv6 messages from clients are sent to the IPv6 multicast address FF02::1:2. All_DHCPv6_Re...
  58. 58Troubleshooting Tasks Troubleshooting Task 1: Resolve Conflicts Similar to IPv4 addresses, an IPv6 address lease can expire on a client that still needs to connect to the network. The "show ipv6 dhcp conflict" command displays any address conflicts logged by the stateful DHCPv6 server. If an IPv6 address conflict is detected, the client typically removes the address and generates a new address using either SLAAC or stateful DHCPv6.Troubleshooting Task 2: Verify Allocation Method
    The show ipv6 interface interface command can be used to verify the method of address allocation indicated in the RA message as indicated by the settings of the M and O flags.
    This information is displayed in the last lines of the output. If a client is not receiving its IPv6 address information from a stateful DHCPv6 server, it could be due to incorrect M and O flags in the RA message.
  59. 59Troubleshooting Tasks Troubleshooting Task 3: Test with a Static IPv6 Address When troubleshooting any DHCP issue, whether it is DHCPv4 or DHCPv6, network connectivity can be verified by configuring a static IP address on a client workstation. In the case of IPv6, if the workstation is unable to reach network resources with a statically configured IPv6 address, the root cause of the problem is not SLAAC or DHCPv6. At this point, network connectivity troubleshooting is required.Troubleshooting Task 4: Verify Switch Port Configuration
    If the DHCPv6 client is unable to obtain information from a DHCPv6 server, verify that the switch port is enabled and is operating correctly.
    Note: If there is a switch between the client and the DHCPv6 server, and the client is unable to obtain the DHCP configuration, switch port configuration issues may be the cause. These causes may include issues from trunking and channeling, STP, and RSTP. PortFast and edge port configurations resolve the most common DHCPv6 client issues that occur with an initial installation of a Cisco switch
  60. 60Troubleshooting Task 5: Test DHCPv6 Operation on the Same Subnet or VLAN If the stateless or stateful DHCPv6 server is functioning correctly, but is on a different IPv6 network or VLAN than the client, the problem may be with the DHCPv6 relay agent. The client facing interface on the router must be configured with the "ipv6 dhcp relay destination" command.Troubleshooting Task 5: Test DHCPv6 Operation on the Same Subnet or VLAN If the stateless or stateful DHCPv6 server is functioning correc...
  61. 61—
  62. 62Verify Router DHCPv6 Configuration A router configured for stateful DHCPv6 services have the address prefix command to provide addressing information. For stateful DHCPv6 services the ipv6 nd managed-config-flag interface configuration mode command is used. For stateless DHCPv6 services the ipv6 nd other-config-flag interface configuration mode command is usedVerify Router DHCPv6 Configuration A router configured for stateful DHCPv6 services have the address prefix command to provide addressing...
  63. 63Debugging DHCPv6 When the router is configured as a stateless or stateful DHCPv6 server, the debug ipv6 dhcp detail command is useful to verify the receipt and transmission of DHCPv6 messages. Ej: a stateful DHCPv6 router has received a SOLICIT message from a client. The router is using the addressing information in its IPV6-STATEFUL pool for binding information.Debugging DHCPv6 When the router is configured as a stateless or stateful DHCPv6 server, the debug ipv6 dhcp detail command is useful to ...

Información

Descripción
CCNA CCNA Fichas sobre E2_10 DHCP, creado por John Dedios el 19/07/2016.
Creado por
John Dedios
Visitas
2
Etiquetas
dhcp
Valoración

Más sobre DHCP and address allocation

Escríbenos

¿Sobre qué es tu mensaje?

¿Qué te parece el nuevo diseño?

¿Te gusta?