We will update answers for you in the shortest time. Thank you! We truly value your contribution to the website. A network administrator wants to examine the active NAT translations on a border router.
Which command would perform the task? Refer to the exhibit. From the perspective of R1, the NAT router, which address is the inside global address? Explanation: There are four types of addresses in NAT terminology. Inside local address Inside global address Outside local address Outside global address The inside global address of PC1 is the address that the ISP sees as the source address of packets, which in this example is the IP address on the serial interface of R1, If more hosts need translation, then a NAT pool of inside global address or overloading should be configured.
A network administrator has just configured address translation and is verifying the configuration. What three things can the administrator verify?
Choose three. Explanation: The show ip nat statistics, show ip nat translationsand debug ip nat commands are useful in determining if NAT is working and and also useful in troubleshooting problems that are associated with NAT. NAT is working, as shown by the hits and misses count. Because there are four misses, a problem might be evident. The standard access list numbered 1 is being used and the translation pool is named NAT as evidenced by the last line of the output.
The PC is sending a request to the web server. Based on the output that is shown, what type of NAT has been implemented? Explanation: The output shows that there are two inside global addresses that are the same but that have different port numbers.
The only time port numbers are displayed is when PAT is being used. The same output would be indicative of PAT that uses an address pool. PAT with an address pool is appropriate when more than 4, simultaneous translations are needed by the company.
Explanation: From the perspective of users behind NAT, inside global addresses are used by external users to reach internal hosts.Post a Comment. It is commonly found in home networks and small businesses where many internal nodes, using an RFC address space such as Use the following diagram for this tutorial.
Here is an accompanying video for this blog post:. In the example above, it's an RFC address, but in the real world, it will usually be an Internet-routable address. Inside local The actual IP address of an inside host. This is often an RFC address that is not routable on the public Internet.
Outside local The IP address of an outside host as it appears to hosts on the inside network. This is how the inside host s see the outside host. Outside global The actual IP address of an outside host, usually assigned by its owner. Don R. He has spoken to audiences worldwide on both technical topics and IT customer service. Posted by Unknown at PM. Labels: ciscocomputerNATnetworknetwork address translationPATport address translationrfcrouterRouter computingTechnology.
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The actual IP on the outside interface that represents one or more inside local IP address to the outside world or network. The actual IP address of an inside host. The IP address of an outside host as it appears to hosts on the inside network. You have permission to reprint this article in your newsletter, blog, website, or publication if you include the following paragraph: Don R.Save Digg Del.
Solutions to many of the problems, either through Cisco IOS Software functionality or through design techniques, are identified. The acronym NAT is used interchangeably to mean network address translation and network address translator software that runs the NAT function.
Show IP NAT Translation
Since that time, users have found NAT to be a useful tool for network migrations and mergers, server load sharing, and creating "virtual servers. Figure depicts a simple NAT function. The NAT replaces device A's private address When device B sends a reply to device A, the destination address of the packet is This packet again passes through the NAT router, and the destination address is replaced with device A's private address.
NAT is transparent to the end systems involved in the translation. In Figuredevice A knows only that its IP address is Device B, on the other hand, thinks the address of device A is That address is "hidden" from device B. NAT can hide addresses in both directions.
Device A thinks device B's address is You can see that the NAT router is translating both the source and destination addresses in both directions to support this address scheme. Cisco NAT devices divide their world into the inside and the outside. Typically the inside is a private enterprise or ISP, and the outside is the public Internet or an Internet-facing service provider. Additionally, a Cisco NAT device classifies addresses as either local or global.
A local address is an address that is seen by devices on the inside, and a global address is an address that is seen by devices on the outside. Given these four terms, an address may be one of four types:. These addresses are not advertised to the outside. These addresses are not advertised to the inside. In Figuredevice A is on the inside and device B is on the outside.
The NAT device tracks these mappings in an address translation table. Example shows the address translation table for the NAT router in Figure This table contains three entries. Reading the entries from the bottom up, the first entry maps OL address The next entry maps the IG address To display the masks used for network addresses and the number of subnets using each mask, use the show ip masks command in EXEC mode.
Network address for which a mask is required. Support in a specific The show ip masks command is useful for debugging when a variable-length subnet mask VLSM is used.
It shows the number of masks associated with the network and the number of routes for each mask. The following is sample output from the show ip masks command:. Optional Displays statistics for limit entries with more than the given number of sessions. Optional Displays statistics for limit entries with less than the given number of sessions. You can use the ip nat translation max-entries all-host command to limit the all-host NAT entries.
When you specify the total keyword with the show ip nat limits all-host command, the output displays only the total entries for a given query.
The following is sample output from the show ip nat limits all-host command:. The inside local or the outside global IP address of the host. The host is the inside local IP address for inside source translations and the outside global IP address for outside source translations.
Number of times a translation entry was not created because of the use count exceeding the configured maximum for the limit entry. When you specify the total keyword with the show ip nat limits all-vrf command, the output displays only the total entries for a given query.
CCNA 3 v7 Modules 6 – 8: WAN Concepts Exam Answers
The following is sample output from the show ip nat limits all-vrf command:. The following is sample output from the show ip nat nvi statistics command:.
Number of translations active in the system. This number is incremented each time a translation is created and is decremented each time a translation is cleared or timed out. List of interfaces marked as NAT enabled with the ip nat enable command. Number of times the software does a translations table lookup, fails to find an entry, and must try to create one. Optional Displays protocol entries. The protocol argument must be replaced with one of the following keywords:. Optional Displays additional information for each translation table entry, including how long ago the entry was created and used.
The following is sample output from the show ip nat nvi translations command:. The following is sample output from the show ip nat redundancy command. The output fields are self-explanatory. This command was modified. The following is sample output from the show ip nat statistics command:. This number is incremented each time a translation is created and is decremented each time a translation is cleared or times out. List of interfaces marked as outside with the ip nat outside command.
List of interfaces marked as inside with the ip nat inside command. Designates that traffic originating from or destined for the interface is subject to NAT.Static NAT is used to do a one-to-one mapping between an inside address and an outside address.
Show IP NAT Statistics Command on CISCO Router/Switch
Static NAT also allows connections from an outside host to an inside host. Usually, static NAT is used for servers inside your network. For example, you may have a web server with the inside IP address Router config ip nat inside source static In our example the private IP address In this example, we will define our internal network as We also have the pool of public IP addresses from When you configure dynamic NAT, you have to define an ACL to permit only those addresses that are allowed to be translated.
We used the same interface configuration as from our static NAT example. This configuration allows addresses in the When an inside host makes a request to an outside host, the router dynamically assigns an available IP address from the pool for the translation of the private IP address. You can configure NAT overload in two ways, depending on how many public IP address you have available. The first case, and one of the most often seen cases, is that you have only one public IP address allocated by your ISP.
In this case, you map all your inside hosts to the available IP address. The configuration is almost the same as for dynamic NAT, but this time you specify the outside interface instead of a NAT pool. Router config access list 1 permit All the inside addresses are translated to the only public IP address available on your router.
Routers are able to recognize the traffic flows by using port numbers, specified by the overload keyword. The second case is that your ISP gave you more than one public IP addresses, but not enough for a dynamic or static mapping.
The configuration is the same as for dynamic NAT, but this time we will add overload for the router to know to use traffic flow identification using port numbers, instead of mapping a private to a public IP address dynamically.
If you feel sometimes works wrong in your configuration, you can always check the NAT translations and statistics with help of the show commands. Router show ip nat statistics. If you have to clear the NAT translation table, you can do it with clear ip nat translation. Router When you begin to troubleshoot, first use the available show commands. If the show commands are not enough, you still have the debug.
Careful when you use debug, because debug commands are using a lot of resource and you may end up disconnected from the router and being unable to reconnect. The first packet of a connection is always process-switched, which is slower. The next packets go through the fast-switched path.
This concludes our lesson. The information found here and in the other two articles is everything you need to know for passing the Cisco CCNA exam. You can also use this information for implementing NAT in real-life, in your home network, or at your job. We will begin by implementing Static NAT.Can anyone shed some light?
The "In use" value of "Display statistics" don't show the number of addresses really used by dhcp clients but show the maximum value of addresses that dhcp server has leased.
Any idea as to why the discrepancy would be so large? That answers my question…thank you very much! I have the same discrepancy. I believe there is something wrong since this is not a common occurrence. I know this is from but this answer is just silly as heck and doesn't even make sense.
The statistics show "in use" and "available" not "highest used". After some brief research I was able to figure out what is actually going on.
If you use the following commands you can see what your server thinks is in use:. I was having the same issue. I had a scope of with 27 of those not assigned. Statistics showed 'In Use'. I tried the netsh solution hoping I could clear up the statistics and avoid IT assignment issues.
That didn't work. I resolved the issue doing the following. Delete the newly added leases and your Statistics will be correct. Office Office Exchange Server. Not an IT pro? Windows Server TechCenter. Sign in. United States English. Ask a question.
Verifying NAT Operation and Basic NAT Troubleshooting
Quick access.The depletion of the public IPv4 address space has forced the internet community to think about alternative ways of addressing networked hosts. Network Address Translation NAT therefore was introduced to overcome these addressing problems that occurred with the rapid expansion of the Internet.
Even if NAT was suggested as a temporary solution, it has been adopted by all network hardware manufacturers, and it is considered a very useful technology, not only for IP address conservation, but also for many other purposes including security. Basically NAT allows a single network device e.
The purpose of this NAT device is to translate the source IP addresses of the internal network hosts into public routable IP addresses in order to communicate with the Internet. This type of NAT allows a maximum of 65, internal connections to be translated into a single public IP. Assume now that we have only one public IP address which is the one configured on the outside interface of our border router.
NAT can be performed both statically and dynamically. Typically the inside is a private enterprise, and the outside is the public Internet. A local address is an address that is seen by devices on the inside, and a global address is an address that is seen by devices on the outside. Given these four terms, an address may be one of four types:.
The specific IP addresses involved are:. You probably know very well how to configure IP addresses on router interfaces, so we skip those configuration steps and move straight to the interesting stuff. This would tell the router that interesting traffic entering or exiting these two interfaces will be subject to address translation. R1 conf term Enter configuration commands, one per line.
Now we would tell the router how to perform address translation and mention which IP addresses source or destination to re-write in packets moving between the inside and outside interfaces.
Here we go:. More specifically the router would identify which of these packets have a source IP address of There are a couple of very useful Cisco IOS commands that can be used to do just that.
Command show ip nat statistics displays the number of static and dynamic NAT translations, inside and outside interfaces, and the number of hits and misses. As you see in the above output, we have one NAT entry configured with Inside global address