Lune de ces solutions, largement mise en oeuvre, est la traduction d’adresses réseau (NAT). NAT est un mécanisme permettant de conserver les adresses IP enregistrées dans des réseaux de grande taille et de simplifier la gestion de l’adressage IP. Lorsqu’un paquet est routé par un équipement de réseau, généralement un pare-feu
It is important to secure your Cisco devices by configuring and implementing username and password protection and assigning different Cisco privilege levels to control and restrict access to the CLI. Hence, protecting the devices from unauthorized access. In this article, we will discuss how to configure user accounts and how to associate them to the different Cisco privilege levels. Then, we’ll take a deep dive into their purposes and functions, as well as their importance in network security Level SecurityCisco IOS devices use privilege levels for more granular security and Role-Based Access Control RBAC in addition to usernames and passwords. There are 16 privilege levels of admins access, 0-15, on the Cisco router or switch that you can configure to provide customized access control. With 0 being the least privileged and 15 being the most privileged. These are three privilege levels the Cisco IOS uses by defaultLevel 0 – Zero-level access only allows five commands- logout, enable, disable, help and 1 – User-level access allows you to enter in User Exec mode that provides very limited read-only access to the 15 – Privilege level access allows you to enter in Privileged Exec mode and provides complete control over the By default, Line level security has a privilege level of 1 con, aux, and vty lines .To assign the specific privilege levels, we include the privilege number when indicating the username and password of the admin1 privilege 0 secret Study-CCNA1 Routerconfigusername admin2 privilege 15 secret Study-CCNA2 Routerconfigusername admin3 secret Study-CCNA3In this example, we assign user admin1 a privilege level of 0. Then, we assign user admin2 to privilege level 15, which is the highest level. For admin3, we did not specify any privilege level, but it will have a privilege level of 1 by try to verify the output of our configuration by logging in to each user. Enter the username and the corresponding password, starting with Access Verification Username admin1 Password Router>? Exec commands disable Turn off privileged commands enable Turn on privileged commands exit Exit from the EXEC help Description of the interactive help system logout Exit from the EXEC Router>Notice in the output above that the user admin1 is under User Exec mode and has only five commands- logout, enable, disable, help, and exit. Now, let’s log in as Access Verification Username admin2 Password Routershow privilege current privilege level is 15 RouterThe output above shows that user admin2 is currently in level 15, and we verified that by typing the show privilege’ command on the CLI. Notice also that we are in Privileged Exec mode. Lastly, let’s log in as Access Verification Username admin3 Password Router>show privilege current privilege level is 1 Router>When we logged in as admin3, we verified that it was in level 1 by typing the show privilege’ command on the CLI. Notice that we are in User Exec Levels 2-14You can increase the security of your network by configuring additional privileges from 2 to 14 and associating them to usernames to provide customized access control. This is suitable when you are designing role-based access control for different users and allowing only certain commands for them to execute. Hence, giving them restrictions to unnecessary commands and increasing the layers of security on the now assign privilege level 5 to a user. After that, we will configure privilege level 5 users to be in User Exec mode and allow them to use the show running-config’ admin4 privilege 5 secret Study-CCNA4 Routerconfigprivilege exec level 5 show running-configAll level 5 users now will be automatically accessing the User Exec mode and can now use the User Exec commands such as show running-config’ on the CLI. Let’s log in as user admin4 to verify Access Verification Username admin4 Password Routershow running-config Building configuration... Current configuration 57 bytes ! boot-start-marker boot-end-marker ! ! ! end RouterEnable Secret Command PrivilegeWe can also configure different privilege levels to passwords. Here, we will allow the enable secret’ command to access the Privileged Exec level. Use the enable secret level {level} {password}’ syntax as shown below. The command sets the enable secret password for privilege level secret level 5 Study-CCNA5We can verify our configuration as shown belowUser Access Verification Username admin5 Password Router>show running-config ^ % Invalid input detected at ^’ marker. Router>enable 5 Password R4show privilege Current privilege level is 5 Routershow running-config Building configuration... Current configuration 57 bytes ! boot-start-marker boot-end-marker ! ! ! end RouterIn our first attempt, notice in the example above that we do not have access to the show running-configuration’ command. That is because we are currently under privilege level 0. However, we can log in as a privilege level 5 user with the enable {privilege level}’ command, and from there, we can now access the show running-configuration’ our Free CCNA Study Guide PDF for complete notes on all the CCNA 200-301 exam topics in one recommend the Cisco CCNA Gold Bootcamp as your main CCNA training course. It’s the highest rated Cisco course online with an average rating of from over 30,000 public reviews and is the gold standard in CCNA training
Page1 – NAT et PAT Page 2 Sommaire 1)Introduction 2)Terminologie 3)NAT statique 4)NAT dynamique 5)Le PAT 6)Configuration 7)Vérification Page 3 1) Introduction Le NAT Scaling IP Addresses - · PDF file Scaling IP Addresses NAT/PAT CCNA 4 .
NAT is a valuable tool for admins, both for conserving public IP addresses and securing internal resources. Several variations of NAT are available, including its cousin PAT. See the differences and learn how to set up PAT using the Cisco IOS. Port Address Translation PAT is a special kind of Network Address Translation NAT. It can provide an excellent solution for a company that has multiple systems that need to access the Internet but that has only a few public IP addresses. Let’s take a look at the distinctions between NAT and PAT and see how they are typically used. Then, I’ll show you how to configure PAT on a Cisco router. Understanding PAT and NATBefore discussing PAT, it will help to describe what NAT does in general. NAT was designed to be a solution to the lack of public IP addresses available on the Internet. The basic concept of NAT is that it allows inside/internal hosts to use the private address spaces 10/8, and networks—see RFC1918, go through the internal interface of a router running NAT, and then have the internal addresses translated to the router’s public IP address on the external interface that connects to the Internet. If you dig into NAT a little deeper, you will discover that there are really three ways to configure it. From these configurations, you can perform a variety of functions. The three configurations are PAT PAT is commonly known as “NAT overload” or sometimes just “overload”. In this configuration, you have multiple clients on your inside network wanting to access an outside network usually the Internet. You have few public IP addresses, many more than the number of clients, so you have to “overload” that real Internet IP address. In other words, you are mapping many inside clients to a single Internet IP address many to one. For an illustration of PAT, see Figure A. Figure A Pooled NAT Pooled NAT is similar to PAT except you have the luxury of having a one-to-one mapping of addresses. In other words, you have just as many inside network clients as you do outside network IP addresses. You tell the NAT router the pool of IP addresses that are available, and each client receives its own IP addresses when it requests a NAT translation. The client does not get the same address each time it requests a translation; it merely gets the next available address from the pool. In my article “Set up NAT using the Cisco IOS,” I explain how to configure Pooled NAT. For an illustration of Pooled NAT, see Figure B. Figure B Static NAT Static NAT is the simplest form of NAT. The most likely example is a mail server on the inside of a private network. The private network connects to the public Internet. In between the two networks, a router performs NAT. For a dedicated server, like a mail server, you would want a static not changing IP address. This way, every time someone on the Internet sends e-mail to the mail server, that server has the same public IP address. For an illustration of Static NAT, see Figure C. Figure C As I said, you can perform a variety of functions with these three configurations. For the purpose of this article, we will focus on configuring PAT. Configuring PATTo configure PAT/NAT correctly the first time, you need to understand the Cisco NAT terminology and how your IP networks/addresses map to each of the entities listed below Inside Local—This is the local IP address of a private host on your network a workstation’s IP address. Inside Global—This is the public IP address that the outside network sees as the IP address of your local host. Outside Local—This is the local IP address from the private network, which your local host sees as the IP address of the remote host. Outside Global—This is the public IP address of the remote host the IP address of the remote Web server that a workstation is connecting to. You’ll configure your Cisco router using seven commands. Let’s assume that your Internet service provider gave you a 30-bit network containing two public IP addresses. This configuration would allow one address for your router and one address for your internal clients and devices. The first command you’ll execute will tell the router which public IP address you want to use for PATip nat pool mypool prefix 30 This command configures a pool range of IP addresses to use for your translation. In this case, we want only one address in our pool, which we will overload. We do this by assigning the same IP address for the start and end of the pool. The next command will tell your router which IP addresses it is allowed to translateaccess-list 1 permit It’s not a good idea to put “permit any” in the access list, even though you will occasionally see that as a recommendation in some sample configurations. The next command isip nat inside source list 1 pool mypool overload This command puts the pool definition and the access list together. In other words, it tells the router what will be translated to what. The overload keyword turns this into a PAT configuration. If you left out overload, you would be able to translate only one IP address at a time, so only one client could use the Internet at a time. Next, you need to tell PAT/NAT what interfaces are the inside network and what interfaces are the outside network. Here’s an exampleinterface ethernet 0ip nat insideinterface serial 0ip nat outside With these commands, your PAT configuration is finished. You have told the Cisco IOS you are translating your network A into a single IP address from network B, that network A is on the ethernet 0 interface and network B is on the serial 0 interface, and that you want to allow the inside network to overload the single IP address on the outside network. Finally, verify that NAT works. This can be as simple as doing a ping command from your inside local host to an outside global host. If the ping succeeds, chances are you have everything configured correctly. You can also use the following Cisco IOS commands to confirm and troubleshootshow ip nat translations [verbose]show ip nat statistics With the translations command, you should see the translation that was created from your ping test. But watch out The translations will disappear after their time-out expires. If you have configured overload, these time-outs are configurable by traffic type. SummaryYou should now understand the differences between PAT, Pooled NAT, and Static NAT, and you should be able to do a basic PAT configuration with the Cisco IOS. For more information, check out the links below. Additional resources TechRepublic “Learn why NAT can cause VPN connection problems” TechRepublic “Set up NAT using the Cisco IOS” TechRepublic “Use NAT to connect your network to the Internet” Cisco NAT Technical Tips Index Cisco How NAT Works Cisco Configuring Network Address Translation Getting Started Cisco Frequently Asked Questions about Cisco IOS NAT Cisco IOS Configuring Network Address Translation Cisco IOS Overloading an Inside Global Address PAT Cisco IOS IP Addressing Command Reference including NAT commands PCWebopedia NAT Definition RFC1631 The IP Network Address Translator NAT RFC1918 Address Allocation for Private Internets Network Computing Network Address Translation Hiding in Plain Sight Verizon How Network Address Translation Works Da Lan Tech Network Address Translation for Beginners Étape3 : Associez la liste de contrôle d’accès nommée au pool NAT et activez la PAT. Étape 4 : Configurez les interfaces NAT. Configurez les interfaces . R2 . avec les commandes NAT

Memento cisco, 2e edition. ios-configuration générale PDF Les équipements Cisco utilisent tous le même système d'exploitation propriétaire, nommé IOS Internetwork Operating System ou, en français, Système d'exploitation pour réseaux interconnectés. La deuxième édition mise à jour de ce mémento présente les aspects réseau liés à ce système à travers un récapitulatif des principales commandes utiles notamment à la configuration d'un routeur et d'un commutateur composition et accès à un routeur, configuration d'un routeur, configuration du routage, NAT et DHCP, filtrage, commutateurs, STP Spanning Tree protocol, VLAN Virtual Local Area Network, et IOSAccès à un routeurSyntaxe IOS et conventionsConfiguration générale d'un routeurConfigurer le routageRedistribution entre protocolesConfiguration NAT/PATConfiguration DHCPFiltrage de paquets avec les ACLAdministration des commutateursConfiguration pour les VLAN

Configurationde routeurs Cisco; Traduction d'adresses NAT/PAT [modifier | modifier le wikicode] Traduction d'adresses réseau (NAT) Network Address Translation. Traduction d'une adresse IP (Internet Protocol) d'un réseau en une adresse IP différente d'un autre réseau. Un réseau est désigné réseau interne et l'autre est le réseau externe. Le réseau interne s'affiche OK nawal....213On va tenter d'autres choses Essaye de réinitialiser Firefox et essaye avec la configuration non modifiée et sans plugins, personas, ...Essaye une réinitialisation usine de ta attention, avant la réinit usine assure toi de disposer de ton identifiant de connexion et du mot de passe associénote tous tes paramétrages spécifiques déjà enregistrés pages WIFI, DHCP, NAT PAT, ...Si la réinitialisation usine ne résoud rien, il te faudra appeler la hotline 3900 ou 3970 si contrat open.Ils te referont probablement refaire tous les tests que tu as déjà faits, il se pourrait qu'ils te proposent un échange de Faites confiance aux produits libres Firefox, Thunderbird, LibreOffice, Irfanview, VLC, 7-zip, FileZillaVotre machine vous en remerciera Toconfigure Port Address Translation, you must specify the inside and outside NAT interfaces as with any NAT configuration. Afterward you’ll need to create an access control list to will be referenced by the NAT translation statement to match inside networks and/or host machines to be translated. If you have multiple public IP addresses and you wish to port address translate to You are here Home / Cisco Routers / Cisco Router Configuration Commands – CLI Cheat Sheet In a previous post, I have published a Cisco Switch Commands Cheat Sheet tutorial. Since these kinds of posts are useful as a reference for many people, I have decided to create also a Cisco Router Commands Cheat Sheet with the most useful and the most frequently used Command Line Interface CLI configuration commands for Cisco Routers. Cisco IOS routers are probably the most complete, versatile and feature-rich networking devices. There are whole books written about Cisco router configurations and commands. Therefore it’s not possible to create a cheat sheet with all of the CLI commands of Cisco routers in one blog post. However, the list below I believe summarizes the most important ones so its a good starting point for a networking professional. Although there is a wide range of Cisco router models, the commands below will work on most devices running IOS with no problems. Make sure to download the cheat sheet in PDF format for future reference by subscribing above. Show/Verification Commands Routershow version [Displays information about running IOS version, hardware model etc] Routershow flash [Displays information about Flash memory] Routershow ip interface brief [Displays interface status and IP addresses for all interfaces] Routershow ip protocols [Displays configured routing protocols such as RIP,EIGRP, OSPF etc] Routershow ip route [Displays the routing table] Routershow cdp neighbors [Displays information about directly connected devices] Routershow cdp neighbors detail [Displays Detailed information about neighboring connected devices] Routershow running-config [Displays currently running configuration] Routershow startup-config [Displays configuration in NVRAM which will be loaded after reboot] Routershow history [Displays all commands in the history buffer] Routershow tech-support [Send the output of this command to Cisco tech support when you open a support ticket in TAC] Saving and Deleting Configurations Routercopy running-config startup-config [Save the running config to NVRAM to be used at next reboot ] Routercopy running-config tftp [Copy the running config to a TFTPserver for backup] Routercopy tftp running-config [Load the saved configuration from TFTP server to DRAM] Routererase startup-config [Delete the startup config from NVRAM Device Name Routerconfighostname MyRouter [Set hostname for the router] Device Security Commands MyRouterconfigenable secret test1 [Sets encrypted secret password for Privilege exec mode “enable” mode] MyRouterconfig line con 0 MyRouterconfig password strongconsolepass MyRouterconfig login [Secure the console with a password] MyRouterconfig line vty 0 4 MyRouterconfig password strongtelnetpass MyRouterconfig login [Secure the telnet terminal lines with a password] MyRouterconfig service password-encryption [Encrypt all passwords on the device] Configuring Router Interfaces Serial interfaces MyRouterconfiginterface s0/0/0 [Entering into serial interface s0/0/0 configuration mode] MyRouterconfig-ifip address [Set ip address and subnet mask on the interface] MyRouterconfig-ifclock rate 64000 [Assign a clock rate] MyRouterconfig-ifno shut [Turns the interface on] Ethernet Ports MyRouterconfigint f0/1 [Entering into ethernet interface fastethernet0/1 configuration mode] MyRouterconfig-ifip address [Set ip address and subnet mask on the interface]] MyRouterconfig-ifno shut [Turns the interface on] Configure Routing Static Routing 1st method MyRouterconfigip route [ Network , = subnet mask of destination network , = next-hop address] 2nd method MyRouterconfigip route serial 0/0/0 [Same as above but instead of gateway you specify the exit interface] MyRouterconfigip route 150 [Set administrative distance of 150 if needed. For static route, default is 1] Default routing MyRouterconfigip route [Send all packets destined for a network not in the routing table to hop] OR MyRouterconfigip route serial 0/0/0 [Send all packets destined for network not in the routing table out serial 0/0/0 interface] Dynamic Routing RIP version 1 MyRouterconfigrouter rip [Enable RIP as routing Protocol] MyRouterconfig-routernetwork [ is the directly connected network we want to advertise] RIP version 2 MyRouterconfigrouter rip [Enable RIP as routing Protocol] MyRouterconfig-routerversion 2 [Enable RIP version 2. Version 1 is default] MyRouterconfig-routernetwork [ is the directly connected network we want to advertise] MyRouterconfig-routerno auto-summary [Turns off auto-summarization- optional] MyRouterconfig-routerauto-summary [Turns on auto summarization – optional] RIP Verification Commands MyRoutersh ip route MyRoutersh ip rip database MyRoutersh ip route rip EIGRP MyRouterconfigrouter eigrp 10 [Enable EIGRP process. 10 is autonomous system AS number, AS can be any number b/w 1 and 65535. All routers should be in the same AS to build a neighbor relationship.] MyRouterconfig-routernetwork [ is the network to advertise] MyRouterconfig-routerno auto-summary [Turns off the auto-summarization – Optional] EIGRP verification commands MyRoutershow ip eigrp neighbors [Displays neighbor table] MyRoutershow ip eigrp interfaces [Displays information for each interface running EIGRP] MyRoutershow ip eigrp topology [Displays the topology table. Shows feasible successors] OSPF MyRouterconfigrouter ospf 10 [Enables OSPF process number 10. Process ID is any number b/w 1-65535. It doesn’t need to be matched with neighbor routers] MyRouterconfig-routernetwork area 0 [Any interface with an address of is to be put into AREA 0 and will advertise and receive OSPF routes] OSPF Authentication Simple MyRouterconfigrouter ospf 10 MyRouterconfig-routerarea 0 authentication [Enables simple authentication. Password will be sent in clear text] MyRouterconfig-routerexit MyRouterconfigint s0/0/0 MyRouterconfig-ifip ospf authentication-key 1234 [Sets password to 1234 for AREA 0 authentication] MD5 Encryption MyRouterconfigrouter ospf 10 MyRouterconfig-routerarea 0 authentication message-digest [Enables MD5 password encryption] MyRouterconfig-routerexit MyRouterconfigint s0/0/0 MyRouterconfig-ifip ospf message-digest-key 10 md5 1234 [10 is the key id. This value must be the same on neighboring routers. Md5 indicates that MD5 algorithm is used and 1234 is the password and must be same on the neighboring routers] OSPF Verification Commands MyRoutershow ip ospf [Displays basic configured ospf information] MyRoutershow ip ospf interfaces [Displays OSPF interfaces information] MyRoutershow ip ospf neighbor [Displays all ospf neighbors and their states] MyRoutershow ip route ospf [Show routes learned by ospf] Configure Access Control Lists MyRouterconfig access-list 101 deny tcp any eq 80 MyRouterconfig access-list 101 permit ip any any [Configure an extended ACL to deny access to port 80 for network and allow everything else] MyRouterconfig interface fastEthernet 1/0 MyRouterconfig-if ip access-group 101 in [Apply ACL 101 in the inbound direction on interface fe1/0] Configure Network Address Translation NAT Dynamic NAT overload PAT MyRouterconfig interface fastEthernet 1/0 MyRouterconfig-if ip nat inside [Specify which interface will be the inside for NAT, the source IPs of packets coming to this interface will be translated] MyRouterconfig interface fastEthernet 1/1 MyRouterconfig-if ip nat outside [Specify which interface will be the outside for NAT, packets going out from this interface will be translated] MyRouterconfig access-list 1 permit MyRouterconfig ip nat inside source list 1 interface fastEthernet 1/1 overload [Access list 1 specifies that inside source network will be translated to the IP address of fastEthernet1/1. Very useful for providing internet access to internal private addresses] Static NAT MyRouterconfig interface fastEthernet 1/0 MyRouterconfig-if ip nat inside MyRouterconfig interface fastEthernet 1/1 MyRouterconfig-if ip nat outside [Define again the inside and outside NAT interfaces] MyRouterconfig ip nat inside source static [Private IP will be translated statically to Public IP one-to-one mapping] DOWNLOAD THE CHEAT SHEET AS PDF FILE Related Posts Comparison of Static vs Dynamic Routing in TCP/IP Networks Cisco OSPF DR-BDR Election in Broadcast Networks – Configuration Example How to Configure Port Forwarding on Cisco Router With Examples Adjusting MSS and MTU on Cisco 800 routers for PPPoE over DSL The Most Important Cisco Show Commands You Must Know Cheat Sheet
Prérequis Avoir quelques notions sur la configuration et l'administration d'un serveur Linux. Avoir quelques notions sur la configuration et l'administration des éléments d'interconnexion Cisco. Avoir mis en place le contexte GSB modifié avec l'ajout d'une DMZ (réalisable avec le contexte de base). Savoir-faire principaux Justifier le choix d’une solution technique de

Network address translation NAT is the process of modifying IP address information in IP packet headers while in transit across a traffic routing are two different types of NATNATStatic NAT The simplest type of NAT provides a one-to-one translation of IP addresses. It is often also referred to as one-to-one NAT. In this type of NAT only the IP addresses, IP header checksum and any higher level checksums that include the IP address need to be changed. The rest of the packet can be left untouched at least for basic TCP/UDP functionality, some higher level protocols may need further translation. Basic NATs can be used when there is a requirement to interconnect two IP networks with incompatible addressing. With static NAT, translations exist in the NAT translation table as soon as you configure static NAT commands, and they remain in the translation table until you delete the static NAT commands.Dynamic NAT Dynamic NAT has some similarities and differences compared to static NAT. Like static NAT, the NAT router creates a one-to-one mapping between an inside local and inside global address and changes the IP addresses in packets as they exit and enter the inside network. However, the mapping of an inside local address to an inside global address happens dynamically. Dynamic NAT sets up a pool of possible inside global addresses and defines matching criteria to determine which inside local IP addresses should be translated with NAT. The dynamic entry stays in the table as long as traffic flows occasionally. With dynamic NAT, translations do not exist in the NAT table until the router receives traffic that requires translation. Dynamic translations have a timeout period after which they are purged from the translation PAT Static PAT translations allow a specific UDP or TCP port on a global address to be translated to a specific port on a local address. Static PAT is the same as static NAT, except that it enables you to specify the protocol TCP or UDP and port for the real and mapped addresses. Static PAT enables you to identify the same mapped address across many different static statements, provided that the port is different for each statement. You cannot use the same mapped address for multiple static NAT statements. With static PAT, translations exist in the NAT translation table as soon as you configure static PAT commands, and they remain in the translation table until you delete the static PAT commands.NAT Overload or PAT It is common to hide an entire IP address space, usually consisting of private IP addresses, behind a single IP address or in some cases a small group of IP addresses in another usually public address space. This type of NAT is called PAT in overload. The dynamic entry stays in the table as long as traffic flows occasionally. With PAT in overload, translations do not exist in the NAT table until the router receives traffic that requires translation. Translations have a timeout period after which they are purged from the translation 1 Static Source NATHow to translate the IP address to the ip the ip nat insideCiscozineconfiginterface fa0/0 Ciscozineconfig-ifip nat insideDefine the ip nat outsideCiscozineconfiginterface fa0/1 Ciscozineconfig-ifip nat outsideDefine the static NAT entryip nat inside source static static NAT, translation exists in the NAT translation table as soon as you configure static NAT command, and it remains in the translation table until you delete the static NAT commandCiscozinesh ip nat translations Pro Inside global Inside local Outside local Outside global - - - CiscozineIf the client sends an ICMP packet or an HTTP request to the web server, the nat table will beCiscozinesh ip nat translations Pro Inside global Inside local Outside local Outside global icmp tcp - - - CiscozineRemember Because the mapped address is the same for each consecutive connection with static NAT, and a persistent translation rule exists, static NAT allows hosts on the destination network to initiate traffic to a translated host if an access list exists that allows it.Example 2 Dynamic Source NATHow to translate the network in the the ip nat insideCiscozineconfiginterface fa0/0 Ciscozineconfig-ifip nat insideDefine the ip nat outsideCiscozineconfiginterface fa0/1 Ciscozineconfig-ifip nat outsideDefine the nat pool used in the NAT translationCiscozineconfigip nat pool dynamic-ip prefix-length 29Define which network will be translatedCiscozineconfigip access-list standard client-list Ciscozineconfig-std-naclpermit the dynamic source NATCiscozineconfigip nat inside source list client-list pool dynamic-ipWith dynamic NAT, translations do not exist in the NAT table until the router receives traffic that requires ip nat translations Ciscozinebut when some packets match the ACL..Ciscozinesh ip nat translations Pro Inside global Inside local Outside local Outside global icmp tcp tcp - - - - - - CiscozineNote If a new packet arrives from yet another inside host, and it needs a NAT entry, but all the pooled IP addresses are in use, the router simply discards the can be checked enabling the “debug ip nat”.Feb 12 1926 NAT translation failed E, dropping packet s= d= user must try again until a NAT entry times out, at which point the NAT function works for the next host that sends a packet. Essentially, the inside global pool of addresses needs to be as large as the maximum number of concurrent hosts that need to use the Internet at the same time—unless we use The main difference between dynamic NAT and a range of addresses for static NAT is that static NAT allows a remote host to initiate a connection to a translated host if an access list exists that allows it, while dynamic NAT does not. You also need an equal number of mapped addresses as real addresses with static 3 Static PATHow to expose two different services on InternetThe Web server is listening on tcp port 80; this server responds on public address from the Internet outside.The SSH server is listening on tcp port 22; this server responds on public address from the Internet outside .Define the ip nat insideCiscozineconfiginterface fa0/0 Ciscozineconfig-ifip nat insideDefine the ip nat outsideCiscozineconfiginterface fa0/1 Ciscozineconfig-ifip nat outsideDefine the static PATThe web server responds on tcp port 80 on the outside’ nat inside source static tcp 80 80The SSH server responds on tcp port 666 on the outside’ interface ; in this case, the real port 22 tcp is translated to the 666 tcp port when a request comes from nat inside source static tcp 22 666Like static NAT, static PAT translation exists in the NAT translation table as soon as you configure static PAT command, and it remains in the translation table until you delete the static PAT ip nat translations Pro Inside global Inside local Outside local Outside global tcp - - tcp - - CiscozineIf an Internet client sends an HTTP request or an SSH Connection on tcp port 666, the nat table will beCiscozinesh ip nat translations Pro Inside global Inside local Outside local Outside global tcp tcp - - tcp tcp - - CiscozineExample 4 PAT – NAT OverloadHow to share an Internet the ip nat insideCiscozineconfiginterface fa0/0 Ciscozineconfig-ifip nat insideDefine the ip nat outsideCiscozineconfiginterface fa0/1 Ciscozineconfig-ifip nat outsideDefine which network will be translatedCiscozineconfigip access-list standard client-list Ciscozineconfig-std-naclpermit the NAT OverloadCiscozineconfigip nat inside source list client-list interface fastethernet0/1 overloadLike dynamic NAT, translations do not exist in the NAT table until the router receives traffic that requires translationCiscozinesh ip nat translations Ciscozinebut when some packets match the ACL..Ciscozineshow ip nat translations Pro Inside global Inside local Outside local Outside global tcp tcp tcp tcp udp udp CiscozineAre there other types of NAT/PAT?The answer is YES! One type of NAT/PAT widely used is the ip nat outside source; this command permits to translate the source address of a packet that enter in the outside’ interface and leave the inside’ simple terms, if you see the first example 1The commandip nat outside source static the to the , so the client must call the ip address to contact the server web and not the particolar type of nat is the ip nat inside destination used when multiple inside devices are identical servers with mirrored content, which from the outside appear to be a single server load define a pool of addresses containing the real hosts’ addresses ending with “type rotary” making the servers available in round-robin fashion. The access list now permits the IP address of the virtual host, what the outside world thinks is the host address. So the virtual host is with the real hosts being through configurationinterface FastEthernet0/0 ip address ip nat inside ! interface FastEthernet0/1 ip address ip nat outside ! ip nat pool real-ip-server prefix-length 24 type rotary ip nat inside destination list 1 pool real-ip-server ! ip route FastEthernet0/1 ! access-list 1 permit translation is not bi-directional in nature. You will have to use a one to one static NAT to accomplish it. A “ip nat inside source static” kind of funtionality can be achieved with the above configuration using a single address in the NAT pool, but that would only work for outside to inside apply nat inside/outside?Typically “ip nat inside” is configured on the interfaces in your local environment which cannot be routed to the Internet typically private range of IP Addresses and and “ip nat outside” on the interface which is connected to the does the router perform NAT?Inside to OutsideIf IPSec then check input access listdecryption – for CET Cisco Encryption Technology or IPSeccheck input access listcheck input rate limitsinput accountingredirect to web cachepolicy routingroutingNAT inside to outside local to global translationcrypto check map and mark for encryptioncheck output access listinspect Context-based Access Control CBACTCP interceptencryptionQueueingOutside to InsideIf IPSec then check input access listdecryption – for CET or IPSeccheck input access listcheck input rate limitsinput accountingredirect to web cacheNAT outside to inside global to local translationpolicy routingroutingcrypto check map and mark for encryptioncheck output access listinspect CBACTCP interceptencryptionQueueingSome useful comandsTo see some statistics about NAT show ip nat statisticsTo see a complete list of the static/dynamic NAT/PAT entries show ip nat translations To clear dynamic nat entry clear ip na translation *To debug NAT debug ip natReferences

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    • configuration nat et pat cisco pdf