CCNA EXPLORATION ACCESSING THE WAN Study Guide Chapter 7: IP Addressing Services 7.1.1 7.1.2 7.1.3 7.1.4 What is DHCP? Typically a network server is used to offer DHCP services. What can be used in a SOHO location? What are the three different address allocation mechanisms DHCP uses when assigning IP addresses? Describe basic dynamic DHCP operation. Describe the four steps in obtaining a lease When the client boots or otherwise wants to join a network. Describe BOOTP. How are BOOTP & DHCP alike? What are the three primary differences between DHCP and BOOTP? How are the message formats different between BOOTP & DHCP? Describe the DHCP message format. How is the DHCPDISCOVER sent? At this point what is the source address of the client? What other services can DHCP provide? What are the steps to configure a router as a DHCP server? Include router commands’ syntax. What command disables DHCP? What command displays a list of all IP address to MAC address bindings that have been provided by the DHCP service? What command displays count information CCNA EXP 4 CH.7 IP Addressing Services 7.1.5 7.1.6 7.1.7 7.1.8 7.2.1 7.2.2 regarding the number of DHCP messages that have been sent and received? What command is used to view multiple pools? What command is used to configure an Ethernet interface as a DHCP client? To renew its IP address what command(s) would be issued on a pc? What is the Cisco IOS helper address? How does the helper address apply in DHCP? What command is needed to configure a router as a DHCP relay agent? By default what other UDP services does the command in the answer above relay? To specify additional ports, what other command is used? What are the steps in configuring a DHCP server using SDM? What command displays all address conflicts recorded by the DHCP server? What command does the server use to detect conflicts? What does the client use to detect clients? What command is used to confirm that the router interface acting as the default gateway for the client is operational? If there is a switch between the client and the DHCP server, what configuration changes resolve the most common DHCP client issues that occur with an initial installation of a Catalyst switch. How do you verify that the client is configured to relay DHCP requests? How do you verify that the router Is receiving DHCP Requests? All public Internet addresses must be registered with what? What is a private address? What are the private internet addresses as defined in RFC1918? Include their CIDR prefix. Without a translation system, private hosts behind a router in the network of one organization cannot connect with private hosts behind a router in other organizations over the Internet. How is this overcome? Describe the NATs basic operation. Where does NAT typically operate? What is the inside network? Outside network? Describe the four types of NAT addresses. Describe Dynamic NAT. Describe Static NAT. Describe NAT overloading. CCNA EXP 4 CH.7 IP Addressing Services 7.2.3 7.2.4 7.2.5 What is another name for NAT overloading? How does PAT track the mappings? Describe this use of port numbers. What happens if a source port is already used? Compare & contrast NAT & PAT. What are the advantages of NAT? What are the disadvantages of NAT? What are the steps to configuring Static NAT? What are the steps to configuring Dynamic NAT? CCNA EXP 4 CH.7 IP Addressing Services 7.2.6 What are the steps to configuring NAT Overload for a Single Public IP Address? What are the steps to configuring NAT Overload for a Pool of Public IP Addresses? CCNA EXP 4 CH.7 IP Addressing Services 7.2.7 7.2.8 7.3.1 What is port forwarding? Describe the operation of port forwarding. What must you do Before using the show commands to verify NAT? What command displays the details of the NAT assignments? How can you see additional information about each translation? What command displays information about the total number of active translations, NAT configuration parameters, how many addresses are in the pool, and how many have been allocated? By default, when do translation entries timeout? How can you change the time-out? What command clears all translations from the NAT table? What are the steps to verify that NAT is operating as expected? What command is used to verify the operation of the NAT feature by displaying information about every packet that is translated by the router? What command generates a description of each packet considered for translation and outputs information about certain errors or exception conditions, such as the failure to allocate a global address? Describe the IPv6 address. After 24 hours. An IPv6 address is a 128-bit binary value, which can be displayed as 32 hexadecimal digits. What are some of the enhancements that IPv6 Enhanced IP addressing offers? Global reachability and flexibility Aggregation Multihoming Autoconfiguration Plug-and-play End-to-end without NAT Renumbering CCNA EXP 4 CH.7 IP Addressing Services What is meant by multihomed hosts? 7.3.2 Describe the IPv6 Address Representation. The text gives the example of 2031:0000:130F:0000:0000:09C0:876A:130B. Describe how this address can be shortened. What is a global unicast address? Describe private IPv6 addresses. Describe the two types of private IPv6 addresses. CCNA EXP 4 Simplified header Routing efficiency Performance and forwarding rate scalability **No broadcasts** No checksums Extension headers Flow labels Mobility and security Mobile IP RFC-compliant IPsec mandatory (or native) for IPv6 Transition richness Dual-stack 6to4 and manual tunnels Translation Hosts attached to multiple physical network segments in an OSI CLNS network. A host can have multiple IP addresses over one physical upstream link. IPv6 addresses use colons to separate entries in a series of 16-bit hexadecimal. Leading zeros in a field are optional. For example, the field 09C0 equals 9C0, and the field 0000 equals 0. So 2031:0000:130F:0000:0000:09C0:876A:130B can be written as 2031:0:130F:0000:0000:9C0:876A:130B. Successive fields of zeros can be represented as two colons "::". However, this shorthand method can only be used once in an address. For example 2031:0:130F:0000:0000:9C0:876A:130B can be written as 2031:0:130F::9C0:876A:130B. An unspecified address is written as "::" because it contains only zeros. An IPv6 unicast address that is globally unique. It can be routed globally w/no modification. It shares the same address format as an IPv6 anycast address. Are assigned by IANA. It consists of a 48-bit global routing prefix and a 16-bit subnet ID. A block of IPv6 addresses is set aside for private addresses, just as is done in IPv4. These private addresses are local only to a particular link or site, and are therefore never routed outside of a particular company network. Private addresses have a first octet value of "FE" in hexadecimal notation, with the next hexadecimal digit being a value from 8 to F. Site-local addresses, are addresses similar to the RFC 1918 Address Allocation for Private Internets in IPv4 today. The scope of these addresses is an entire site or organization. However, the use of site-local addresses is problematic and is CH.7 IP Addressing Services What is the IPv6 loopback address? Describe the IPv6 Unspecified Address. being deprecated as of 2003 by RFC 3879. In hexadecimal, site-local addresses begin with "FE" and then "C" to "F" for the third hexadecimal digit. Link-local addresses, are new to the concept of addressing with IP in the Network layer. These addresses have a smaller scope than site-local addresses; they refer only to a particular physical link (physical network). Routers do not forward datagrams using link-local addresses at all, not even within the organization; they are only for local communication on a particular physical network segment. They are used for link communications such as automatic address configuration, neighbor discovery, and router discovery. Many IPv6 routing protocols also use link-local addresses. Link-local addresses begin with "FE" and then have a value from "8" to "B" for the third hexadecimal digit. Just as in IPv4, a provision has been made for a special loopback IPv6 address for testing; datagrams sent to this address "loop back" to the sending device. However, in IPv6 there is just one address, not a whole block, for this function. The loopback address is 0:0:0:0:0:0:0:1, which is normally expressed using zero compression as "::1". In IPv4, an IP address of all zeroes has a special meaning; it refers to the host itself, and is used when a device does not know its own address. In IPv6, this concept has been formalized, and the all-zeroes address (0:0:0:0:0:0:0:0) is named the "unspecified" address. It is typically used in the source field of a datagram that is sent by a device that seeks to have its IP address configured. You can apply address compression to this address; because the address is all zeroes, the address becomes just "::". Describe how additional hierarchy is added to the 48-bit global routing prefix with the registry prefix, ISP Prefix, and site prefix. Describe the interface id. Describe the four ways you can assign an IPv6 address ID statically or dynamically. Give commands as needed. CCNA EXP 4 IPv6 addresses use interface identifiers to identify interfaces on a link. Think of them as the host portion of an IPv6 address. Interface identifiers are required to be unique on a specific link. Interface identifiers are always 64 bits and can be dynamically derived from a Layer 2 address (MAC). Manual Interface ID Assignment: manually assign both the prefix (network) and interface ID (host) portion of the IPv6 address. To configure an IPv6 address on a Cisco router interface, use the ipv6 address ipv6-address/prefix-length command in interface configuration mode. Example: RouterX(config-if)#ipv6 address 2001:DB8:2222:7272::72/64 CH.7 IP Addressing Services Describe the EUI-64 interface. 7.3.3 Describe Dual Stacking. Describe Tunneling. Describe NAT-Protocol Translation (NAT-PT). CCNA EXP 4 EUI-64 Interface ID Assignment: to configure the prefix (network) portion of the IPv6 address and derive the interface ID (host) portion from the Layer 2 MAC address of the device, which is known as the EUI-64 interface ID. To configure an IPv6 address on a Cisco router interface and enable IPv6 processing using EUI-64 on that interface, use the ipv6 address ipv6-prefix/prefix-length eui-64 command in interface configuration mode. Example: RouterX(config-if)#ipv6 address 2001:DB8:2222:7272::/64 eui-64 Stateless Autoconfiguration: automatically configures the IPv6 address. In IPv6, it is assumed that non-PC devices, as well as computer terminals, will be connected to the network. The autoconfiguration mechanism was introduced to enable plug-and-play networking of these devices to help reduce administration overhead. DHCPv6 (Stateful): enables DHCP servers to pass configuration parameters, such as IPv6 network addresses, to IPv6 nodes. It offers the capability of automatic allocation of reusable network addresses and additional configuration flexibility. This protocol is a stateful counterpart to IPv6 stateless address autoconfiguration (RFC 2462), and can be used separately or concurrently with IPv6 stateless address autoconfiguration to obtain configuration parameters. Extended Universal Identifier: an IPv6 address format created by taking an interface’s MAC add.—48 bits in length—and inserting another 16-bit hexadecimal string (FFFE) between the OUI (1ST 24 bits) & unique serial number (last 24 bits) of the MAC add. To ensure that the chosen add. Is from a unique Ethernet MAC add., the 7th bit in the high order byte is set to 1(equivalent to the IEEE G/L bit) to indicate the uniqueness of the 48-bit address. 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. Router and switches are configured to support both protocols, with IPv6 being the preferred protocol. There are several tunneling techniques available, including: 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. Cisco IOS Release 12.3(2)T and later (with the appropriate feature set) also include NAT-PT between IPv6 and IPv4. This translation allows direct communication between hosts that use different versions of the IP protocol. These translations CH.7 IP Addressing Services 7.3.4 Describe the basic operation of dual stacking. Describe API. What command(s) enable the use of IPv6 on a router? 7.3.5 Describe IPv6 Tunneling. What two issues arise from tunneling? What considerations are a must for a manually configured tunnel? 7.3.6 If IPv4 uses CIDR, what does IPv6 use? What are the IPv6 routing control plane considerations? CCNA EXP 4 are more complex than IPv4 NAT. At this time, this translation technique is the least favorable option and should be used as a last resort. Dual stacking is an integration method that allows a node to have connectivity to an IPv4 and IPv6 network simultaneously. Each node has two protocol stacks with the configuration on the same interface or on multiple interfaces. A dual-stack node chooses which stack to use based on the destination address of the packet. A dual-stack node should prefer IPv6 when it is available. Old IPv4-only applications continue to work as before. New and modified applications take advantage of both IP layers. A new application programming interface (API) has been defined to support IPv4 and IPv6 addresses and DNS requests. An API facilitates the exchange of messages or data between two or more different software applications. Use the global configuration command ipv6 unicast-routing. This command enables the forwarding of IPv6 datagrams. You must configure all interfaces that forward IPv6 traffic with an IPv6 address using the ipv6 address IPv6-address [/prefix length] interface command. Tunneling is an integration method where an IPv6 packet is encapsulated within another protocol, such as IPv4. This method enables the connection of IPv6 islands without needing to convert the intermediary networks to IPv6. When IPv4 is used to encapsulate the IPv6 packet, a protocol type of 41 is specified in the IPv4 header, and the packet includes a 20-byte IPv4 header with no options and an IPv6 header and payload. It also requires dual-stack routers. The maximum transmission unit (MTU) is effectively decreased by 20 octets if the IPv4 header does not contain any optional fields. In addition, a tunneled network is often difficult to troubleshoot. The end routers must be dual stacked, and the configuration cannot change dynamically as network and routing needs change. It uses longest prefix match routing. IPv6 address size - Address size affects the informationprocessing functions of a router. Systems using a 64-bit CPU, bus, or memory structure can pass both the IPv4 source and destination address in a single processing cycle. For IPv6, the source and destination addresses require two cycles eachfour cycles to process source and destination address information. As a result, routers relying exclusively on software processing are likely to perform slower than when in an IPv4 environment. Multiple IPv6 node addresses - Because IPv6 nodes can use several IPv6 unicast addresses, memory consumption of the Neighbor Discovery cache may be affected. IPv6 routing protocols - IPv6 routing protocols are similar to their IPv4 counterparts, but since an IPv6 prefix is four times CH.7 IP Addressing Services What are the IPv6 routing forwarding/data plane considerations? How does the RIPNg Routing Protocol differ using IPv6? What is RIPng? What are some of the features of RIPng? 7.3.7 In dual stack deployments which protocol is used? What are the two steps to activate IPv6 on a router? List the appropriate commands. CCNA EXP 4 larger than an IPv4 prefix, routing updates have to carry more information. Routing table Size -Increased IPv6 address space leads to larger networks and a much larger Internet. This implies larger routing tables and higher memory requirements to support them. Parsing IPv6 extension headers - Applications, including mobile IPv6, often use IPv6 address information in extension headers, thus increasing their size. These additional fields require additional processing. For example, a router using ACLs to filter Layer 4 information needs to apply the ACLs to packets with extension headers as well as those without. If the length of the extension header exceeds the fixed length of the hardware register of the router, hardware switching fails, and packets may be punted to software switching or dropped. This severely affects the forwarding performance of the router. IPv6 address lookup - IPv6 performs a lookup on packets entering the router to find the correct output interface. In IPv4, the forwarding decision process parses a 32-bit destination address. In IPv6, the forwarding decision could conceivably require parsing a 128-bit address. Most routers today perform lookups using an application-specific integrated circuit (ASIC) with a fixed configuration that performs the functions for which it was originally designed IPv4. Again, this could result in punting packets into slower software processing, or dropping them all together. IPv6 routes use the same protocols and techniques as IPv4. Although the addresses are longer, the protocols used in routing IPv6 are simply logical extensions of the protocols used in IPv4. Routing Information Protocol next generation (RIPng) as a simple routing protocol based on RIP. It provides a simple way to bring up an IPv6 network without having to build a new routing protocol. It is a distance vector routing protocol with a limit of 15 hops that uses split horizon and poison reverse updates to prevent routing loops. Its simplicity comes from the fact that it does not require any global knowledge of the network. Only neighboring routers exchange local messages. Based on IPv4 RIP version 2 (RIPv2) and is similar to RIPv2 Uses IPv6 for transport Includes the IPv6 prefix and next-hop IPv6 address Uses the multicast group FF02::9 as the destination address for RIP updates (this is similar to the broadcast function performed by RIP in IPv4) Sends updates on UDP port 521 Is supported by Cisco IOS Release 12.2(2)T and later Both RIP and RIPng are required. Step1. Activate IPv6 traffic-forwarding on the router. Use the global command ipv6 unicast-routing. CH.7 IP Addressing Services What are two ways to perform name resolution from the Cisco IOS software process? 7.3.8 How do you configure RIPng with IPv6? What is used instead of the network command in RIPng? 7.3.9 Step 2. Configure each interface that requires IPv6. Use the ipv6 address interface command. You can completely specify the IPv6 address or compute the host identifier (rightmost 64 bits) from the EUI-64 identifier of the interface. Define a static name for an IPv6 address using the ipv6 host name [port] ipv6-address1 [ipv6address2...ipv6-address4] command. You can define up to four IPv6 addresses for one hostname. The port option refers to the Telnet port to be used for the associated host. Specify the DNS server used by the router with the ip name-server address command. The address can be an IPv4 or IPv6 address. You can specify up to six DNS servers with this command. Before configuring the router to run IPv6 RIP, globally enable IPv6 using the ipv6 unicast-routing global configuration command, and enable IPv6 on any interfaces on which IPv6 RIP is to be enabled. 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. 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. What are some of the commands used to troubleshoot RIPng problems? CCNA EXP 4 CH.7 IP Addressing Services CCNA EXP 4 CH.7 IP Addressing Services