PAT – Port Address Translation – plays a huge role in IPv4 networks. Today’s post looks at the simpler of the two configuration options for router NAT configuration a single router interface IP address as in the inside global address. Jump in for your next bit of 5-10 minutes of practice! All about Config LabsThe blog has a series of lab exercises called “Config Labs.” Each lab presents a topology with the relevant initial configuration for each device. -action="collapse">Answer Options - Click Tabs to RevealOption 1 Paper/EditorOption 2 Cisco Packet TracerOption 3 Cisco Modeling LabsOption 1 Paper/Editor You can learn a lot and strengthen real learning of the topics by creating the configuration – even without a router or switch CLI. In fact, these labs were originally built to be used solely as a paper exercise! To answer, just think about the lab. Refer to your primary learning material for CCNA, your notes, and create the configuration on paper or in a text editor. Then check your answer versus the answer post, which is linked at the bottom of the lab, just above the comments section. Option 2 Cisco Packet Tracer You can also implement the lab using the Cisco Packet Tracer network simulator. With this option, you use Cisco’s free Packet Tracer simulator. You open a file that begins with the initial configuration already loaded. Then you implement your configuration and test to determine if it met the requirements of the lab. Use this link for more information about Cisco Packet Tracer. Use this workflow to do the labs in Cisco Packet Tracer Download the .pkt file linked below. Open the .pkt file, creating a working lab with the same topology and interfaces as the lab exercise. Add your planned configuration to the lab. Test the configuration using some of the suggestions below. Download this lab’s Packet Tracer File Option 3 Cisco Modeling Labs You can also implement the lab using Cisco Modeling Labs – Personal CML-P. CML-P or simply CML replaced Cisco Virtual Internet Routing Lab VIRL software in 2020, in effect serving as VIRL Version 2. If you prefer to use CML, use a similar workflow as you would use if using Cisco Packet Tracer, as follows Download the CML file filetype .yaml linked below. Import the lab’s CML file into CML and then start the lab. Compare the lab topology and interface IDs to this lab, as they may differ more detail below. Add your planned configuration to the lab. Test the configuration using some of the suggestions below. Download this lab’s CML file! Network Device Info The CML topology matches the lab topology. Lab Answers Below Spoiler AlertLab Answers Configuration Click Tab to RevealLab ConfigurationLab Configuration Answers Figure 1 PAT Topology interface GigabitEthernet0/1 ip nat inside!interface GigabitEthernet0/2 ip nat outside!ip nat inside source list 1 interface GigabitEthernet0/2 overload!access-list 1 permit Example 3 R1 Config Commentary, Issues, and Verification Tips Click Tabs to RevealLab CommentaryKnown Packet Tracer IssuesVerification Tips for CPT/CMLLab Commentary Commentary There are several ways to configure NAT, including static NAT, dynamic NAT, and Port Address Translation PAT. Static NAT is typically used for one-to-one translations from a specific inside address called an inside local address to a specific outside address called an inside global address. Dynamic NAT differs slightly because it allocates the outside address from a configured pool rather than pre-determining the specific address to use in each case. The third major type of NAT, PAT or NAT overload, uses either a specific outside address or a configured pool. The difference between PAT and the other types is that the mapping is not one-to-one from an inside address to an outside address. With PAT, there is a many-to-one mapping between the inside local address and the inside global address using unique TCP and UDP port numbers to decide where and how to translate the packets. For this lab, you were tasked with configuring PAT using R1’s G0/2 interface IP address for translations and access list 1. The ACL should match only R1’s LAN connecting to S1, S2, and S3. Once this is configured, the last step is to configure a PAT statement to use R1’s G0/2 interface and the ACL to map entries from R1’s LAN to its interface IP address. First, you have to determine which interfaces connect to hosts inside the network and connect to hosts outside the network. For this lab, R1’s G0/1 interface is connected to S1, S2, and S3 and is considered the inside interface. To configure this, use the ip nat inside command while in interface configuration mode. R1’s G0/2 interface is connected to R2 and is considered the outside interface. To configure this, use the ip nat outside command while in interface configuration mode. The second task to perform is to configure the ACL to match R1’s LAN connecting to S1, S2, and S3, all in subnet The global command access-list 1 permit configures the entire ACL. The third and final task uses one long command that ties four ideas together Packets entering interfaces per the source keyword Packets matching the logic in ACL 1 To use one inside global address – the address of the G0/2 interface To use the PAT overload feature The command ip nat inside source list 1 interface GigabitEthernet0/2 overload. Also, note that the requirements tell you to configure static routes on R2 as needed for the inside global addresses. In this case, the configuration uses a range of addresses in the subnet between R1 and R2, so R2 already has a connected route that includes the addresses used by NAT. So there is no need for any additional static routes. Known Packet Tracer Issues Known Issues in this Lab This section of each Config Lab Answers post hopes to help with those issues by listing any known issues with Packet Tracer related to this lab. In this case, the issues are Summary Detail 1 Occasional incorrect NAT show command output based on sequencing CPT may show incorrect NAT behavior if you configure NAT and then move directly to testing. You might want to configure, then save and re-open the .pkt file before testing. Why Would Cisco Packet Tracer Have Issues? Note The below text is the same in every Config Lab. Cisco Packet Tracer CPT simulates Cisco routers and switches. However, CPT does not run the same software that runs in real Cisco routers and switches. Instead, developers wrote CPT to predict the output a real router or switch would display given the same topology and configuration – but without performing all the same tasks, an actual device has to do. On a positive note, CPT requires far less CPU and RAM than a lab full of devices so that you can run CPT on your computer as an app. In addition, simulators like CPT help you learn about the Cisco router/switch user interface – the Command Line Interface CLI – without having to own real devices. CPT can have issues compared to real devices because CPT does not run the same software as Cisco devices. CPT does not support all commands or parameters of a command. CPT may supply output from a command that differs in some ways from what an actual device would give. Those differences can be a problem for anyone learning networking technology because you may not have experience with that technology on real gear – so you may not notice the differences. So this section lists differences and issues that we have seen when using CPT to do this lab. Verification Tips for CPT/CML Beyond comparing your answers to this lab’s Answers post, you can test in Cisco Packet Tracer CPT or Cisco Modeling Labs CML. In fact, you can and should explore the lab once configured. For this lab, once you have completed the configuration, try these verification steps. Verify the dynamic PAT configuration by checking the reachability from S1, S2, and S3 to R2 using ping. At router R1, using the show ip nat translations command to verify that the NAT table begins with no entries. From S1/S2/S3, try the ping command, pinging R2’s global address, which tests the static NAT configuration. At router R1, using the show ip nat translations command to verify a new NAT table entry appeared in support of each flow. Pay close attention to the port numbers used and the fact that all translation table entries use the same outside global address, just with different port numbers. Use a TCP or UDP app to test from S1/S2/S3 to router R2. For instance, use Telnet. Because the initial configuration did not prepare router R2 for inbound Telnet, add configuration on R2 as follows line vty 0 15 transport input all login password cisco From S1/S2/S3, try the telnet command, pinging R2’s global address, which tests the static NAT configuration. At router R1, using the show ip nat translations command to verify a new NAT table entry appeared in support of each flow. More Labs with Related Content! By Wendell Odom October 15, 2021 1305 Write a commentNo Comments View commentsWrite a comment
GW2(config)# interface fastethernet 0/1. GW2 (config-if)# standby 1 ip . GW2 (config-if)# standby 1 preempt. GW2 (config-if)# exit. You do not need to do this HSRP Cisco Configuration for both sides, but in this configuration, we do it for both sites. After this you can check the configuration with “show standby” command on GW1
SommaireI. PrésentationII. Configuration du réseauIII. Configuration du routeurIV. Configuration du NATV. Test du NATVI. A vos claviers I. Présentation Le NAT ou "Network Address Translation" est une bonne réponse aux problématiques de routage que l'on peut rencontrer lorsque l'on souhaite lier un réseau dit "privé" c'est à dire sur lequel nous avons la main à un réseau dit "publique" sur lequel nous ne pouvons modifier la configuration. Le but du NAT quand il est mit sur un routeur séparant deux réseaux comme ceux-ci est de faire passer toutes les requêtes provenant du réseau privé que nous identifierons comme le LAN comme des requêtes provenant de ce routeur est nous d'un élément derrière lui possédant un autre adressage. Souvent, la problématique à laquelle peut répondre le NAT est la suivante Schéma de base où le NAT pourrait intervenir On voit ici que le réseau "privé" en vert se situe derrière le routeur R2 sur lequel nous avons la main. Pour joindre les réseaux derrière R1, il nous faut mettre une route disant qu'il faut sortir par l'interface WAN du R2. En revanche, le routeur R1 ne saura pas faire revenir les paquets car il ne possède pas de route vers notre réseau LAN Souvent, on arrive à pinguer avec l'interface externe du Routeur frontière mais pas l'interface qui lui est liée Le schéma ci-dessus illustre le cas de figure dans lequel on se retrouve souvent lorsque nous devons mettre en place du NAT. Le fait que le ping vers le routeur R1 ne fonctionne pas alors que celui sur l'interface externe du R2 fonctionne vient du fait que les paquets de réponse du routeur R1 n’empruntent pas le bon chemin car R1 ne connait pas le réseau privé et ne possède donc pas de route permettant de faire revenir les autre fonction du du NAT est de sécuriser une partie du réseau en la cachant à une autre partie. Cela est utile en terme de sécurité quand un réseau privé est adjacent à un réseau public et que l’on peut voir ce réseau local depuis le réseau public. Plus clairement, le routeur R2 va changer toutes les trames IP provenant du LAN en mettant comme IP source son IP sur le réseau WAN. Cela permettra de ne pas divulguer des IP du LAN à d'autres éléments du réseau et également de faire en sorte ces paquets reviennent car l'IP source sera sur un réseau connus des autres éléments du réseau. Le principe du NAT est simple, le routeur fait office de barrière entre le réseau outside celui auquel on cache et le réseau inside celui que l’on cache . Ainsi chaque requête provenant du réseau inside vers l’outside sera cachée par le NAT du routeur. On dit qu'une NAT est dynamique lorsque les adresses sources ici venant du LAN sont translaté de façon dynamique par des ports différents ou par des IP différentes si on en dispose vers l'interfaces de sorties ici WAN. Le routeur remplie sa table NAT de façon dynamique à l'inverse du NAT statique ou les translations sont saisies et enregistrés à l'avance II. Configuration du réseau Pour mettre en place notre infrastructure, nous allons travailler sur l'architecture présentée plus haut, détaillée au niveau réseau ici Schéma pour mettre en place notre NAT Nous allons donc ici mettre en place notre NAT dynamiques sur le routeur R2. Ici, les routeurs R1 et R2 peuvent communiquer ensemble, mais le routeur R1 ne connais pas la route vers le réseau donc il ne sait pas faire revenir les paquets s'ils ont été émis par les postes du LAN. En revanche, si R2 changent l'IP source des trames provenant du LAN en mettant sa propre IP, R1 saura y répondre, R2 fera alors la translation dans l'autre sens pour faire revenir les paquets à sa source. Ce processus est illustré dans le schéma suivant Schématisation du processus de Translation d'adresse NAT On va a présent configurer notre routeur R2 R2>enable R2configure terminal R2configinterface fa0/0 R2config-ifip address R2config-ifno shutdown R2config-ifexit R2configinterface fa0/1 R2config-ifip address R2config-ifno shutdown R2config-ifexit A ce stade, les deux réseaux sont reliés mais chacun peut voir la présence de l’autre. nous voulons que le réseau ne puisse pas joindre le réseau mais que l’inverse soit possible. IV. Configuration du NAT On doit ensuite indiquer quelle interface sera à l'intérieur du NAT "inside" et quelle interface sera à l'extérieur "outside". Cela permettra de dire au routeur dans quel sens il doit affecter les translations d'adresses. Ici, l'interface Fa0/0 sera l'interface Inside et l'interface Fa0/1 sera l'interface Outside. R2configinterface fa0/0 R2config-ifip nat inside R2config-ifexit R2configinterface fa0/1 R2config-ifip nat outside R2config-ifexit On va ensuite créer les règles d'accès qui permettra au LAN de sortir du NAT R2configaccess-list 1 permit R2configip nat inside source list 1 interface fa0/1 overload Le processus de translation d'adresse est maintenant opérationnel. V. Test du NAT Pour vérifier que notre routeur est bien en mode NAT, nous devrions pouvoir communiquer à présent avec le routeur R1 depuis le poste LAN. Avant cette communication, nous pouvons saisir la commande suivante dans notre routeur R2 R2debug ip nat On va ensuite communiquer avec notre routeur R1 et nous devrions voir les étapes de translation d'adresse s'afficher Debug de la translation d'adresse NAT sur le routeur Cisco Cette commande permet de voir les paquets qui transitent au travers du routeur en utilisant le NAT, ainsi nous voyons le processus d'action du NAT sur le paquet. VI. A vos claviers Je vous propose à présent de mettre en application ce tutoriel via un exercice packet tracer que je vous ai préparé. Il vous suffit pour cela de télécharger le fichier .pka suivant et de vous assurer que Packet Tracer version 6 est installé sur votre poste pour le lancer
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
Configuring static NAT on Cisco devices With static NAT, routers or firewalls translate one private IP address to a single public IP address. Each private IP address is mapped to a single public IP address. Static NAT is not often used because it requires one public IP address for each private IP address. To configure static NAT on Cisco devices using Network Configuration Manager, you can create the corresponding Configlet commands and push them in multiple devices. If you don't have NCM installed, please click here to download and install the application. To configure static NAT on Cisco devices, following steps are required Configure private/public IP address mapping by using the ip nat inside source static PRIVATE_IP PUBLIC_IP command Configure the router’s inside interface using the ip nat inside command Configure the router’s outside interface using the ip nat outside command Steps to configure static NAT on Cisco devices through CLI Login to the device using SSH / TELNET and go to enable mode. Go into the config mode. Routerconfigure terminal Enter configuration commands, one per line. End with CNTL/Z. Routerconfig Use below command to configure static NAT Routerconfigip nat inside source static Configure the router's inside interface Routerconfiginterface fa0/0 Routerconfig-ifip nat inside Routerconfig-ifexit Configure the router's outside interface Routerconfiginterface fa0/1 Routerconfig-ifip nat outside Routerconfig-ifexit Exit config mode Routerconfigexit Router Execute show ip nat translations command to view the NAT configuration. Copy the running configuration into startup configuration using below command Routerwrite memory Building configuration... [OK] Router The corresponding configlet can be created in NCM application as shown in below screenshot. Also you can click the below button to download the Configlet as XML and import it into NCM application using file import option. Configlet Name Configure Static NAT - Cisco Description This configlet is used to configure static NAT in Cisco devices. Execution Mode Script Execution Mode Configlet Content configure terminal ip nat inside source static $PRIVATE_IP $PUBLIC_IP interface $INSIDE_INTF ip nat inside exit interface $OUTSIDE_INTF ip nat outside exit exit show ip nat translations write memory
commutateurset versions de Cisco IOS peuvent être utilisés. Selon le modèle et la version de Cisco IOS, les Selon le modèle et la version de Cisco IOS, les commandes disponibles et le résultat produit peuvent varier de ceux indiqués dans les travaux pratiques.
The hardest thing about NAT in Cisco routers and ASA firewalls is understanding how to use the technology in real life. Tons of guide papers have been written, the Internet is full of gigabytes of information on the topic, yet the subject remains relevant. Truth is, 95% of absolute majority of people will only need to use just one of the two types of connections. 1 PAT Port Address Translation A bunch of internal IP addresses are translated into a single external IP address when connecting to the outside world. While each packet destined to outside networks is being processed by a router or a Cisco ASA, the correlation of the actual internal IP address and port number of the source of the TCP connection is being remembered, which allows to correctly perform the reverse translation and transfer return packets. This kind of NAT is used when you need to allow access FROM an internal network to external resources such as the Internet. 2 Static NAT This is translating addresses one-to-one. A specific public IP address is put together with an internal IP address. This kind of NAT translation is used when you need access FROM the outside world to a server or resource within the internal network or a DMZ. Summary If you need access from the internal LAN to the outside world, it is most likely that you will have to configure PAT. If you need access from the outside world to a certain internal resource, then you will have to configure static NAT. NAT configuration examples for the above cases Cisco ASA IOS below PAT global outside 1 interface nat inside 1 Static NAT static dmz,outside interface netmask Important! The keyword interface in this code specifies the devices own IP address that is assigned to the external interface If the translation is being made into another IP address from the pool of IP addresses belonging to the external interface, then that address is specifically mentioned. Cisco ASA IOS above PAT object-group network NET_LAN network-object nat inside,outside source dynamic NET_LAN interface Static NAT object network host nat dmz,outside static interface Cisco IOS Router PAT interface Ethernet X ip address ip nat inside interface Ethernet Y ip address ip nat outside ip nat pool POOL_PAT //No mistakes here. An external address is mentioned twice. ip access-list standard ACL_PAT permit ip ip nat inside source list ACL_PAT pool POOL_PAT overload Static NAT interface Ethernet Z ip address ip nat inside interface Ethernet Y ip address ip nat outside ip nat inside source static interface Ethernet Y Important! This article includes only the simplest configuration examples for NAT translations, on purpose. More complex examples are covered in articles about basic Cisco router and Cisco ASA configurations. Also there is a full explanation of port forwarding static NAT on Cisco ASA with configuration examples in this article. This article was written by Alexey Yurchenko Back to Table of contents
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configuration nat et pat cisco pdf
