Questions tagged [nat]

For questions about Network Address Translation (NAT), a method of modifying network address information in IPv4 packet headers.

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Allow only specified set of IPs to use external port on pfSense

I have a pfsense router and a NAT rule that allows a port redirect. | GitHub | - ( Internet ) - [pfsense] -net port translation- [ Jenkins ] I want gitHub to be able to reach my jenkins, but no other ...
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Silent VOIP call in one direction [closed]

I have been working on a problem with some VOIP phones in one of my branches at work, Phone A - Yealink T23P in my test lab - number/username ends 2022 Phone B - Yealink T46G in the branch - number/...
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Why do we need private IP address range?

When it comes to local networks, you have the freedom to use any IP address you want for your network since it doesn't need to communicate on the internet with other devices. However, the RFC ...
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2answers
80 views

Why cant't IPSec's Transport Mode ESP be used in NAT64 although ESP doesn't sign the new IP header?

In RFC6146 stated: Any protocols that protect IP header are incompatible with NAT64. This implies that end-to-end IPsec verification will fail when the Authentication Header (AH) is used (both ...
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2answers
40 views

Help understanding NAT/PAT - With example

Would anyone be able to clarify what ive been thinking is correct or if this is a complete misunderstanding and possibly answer these questions if you have time? So I understand that NAT/PAT is giving ...
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1answer
945 views

using NAT with a difference IP/range from the outside interface + proxy ARP

I need to NAT the source address of the traffic from my local LAN going out of the ASA firewall. From the diagram above, my outside interface IP on the ASA firewall is set at 192.168.12.2 q1) Am i ...
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2answers
15 views

Concurrent site-to-site VPN tunnels through dual ISPs (with 2 couples of Cisco ASA) between same devices

I currently have a simple site-to-site VPN setup, connecting machines from site 1 to site 2 through 1 ISP, using a set of ASA 5506X. All is good. I'd like to "double" that setup for ...
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32 views

Masking all IP Addresses in a subnet to appear as one IP Address on the main network Using Siemens S615

I am trying to create a network setup that would take many devices that are working together and have them appear as one device or IP on a network using a Siemens Scalance S615. The setup would be as ...
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2answers
33 views

PIM Packet and NAT

Is it possible to NAT PIM Join packet? Assume the receiver and the source are in two different private network. Thus NAT is required. The upstream source and the groupe are included in the PIM Join ...
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1answer
103 views

Can a server on the other end of a site-to-site vpn be exposed (NATd) to a public IP on an ASA

AWS DataCenter ----------- site-to-site VPN ------------ http server <=======================> Cisco ASA public address 10.0.1.59:443 ...
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1answer
60 views

Packets lost with correct TCP sequence number. Is it possible?

I'm analysing some communication issues that we have between a server (SCADA) and remote terminal units (RTU) that we have in the field. The communications are IEC104 protocol which use TCP/IP. The ...
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2answers
75 views

Cisco Port forward ip nat inside source static … Invalid

This is almost the same question as How to setup port forwarding on Cisco Router running Version 15.2(4)M6. The problem is that the command used in the answer is not available: ip nat inside source ...
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2answers
836 views

Access internal webserver with domainname points to external IP

We have a webserver on our LAN. Externally, we can use the public domainname (let's say business.com) to access the website. Internally, we need to use the local IP. We also want to use the public ...
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1answer
878 views

pfSense 1:1 NAT Not Working

Next year, if I have the money for it, I want to get a dedicated server (either from Hetzner or OVH) and some IPs (maybe like 16 IPs). The server will have Proxmox and VMs will get their network ...
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1answer
29 views

IP masquerading and nat

what is the difference between IP masquerading and nat? do both of them have the same limitation? in the line "IP masquerading cannot provide full internet connections to the hosts which hide ...
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2answers
219 views

Nat ACL Question?

I am so confused with fundamentals that I used to be an expert in, so I have this topology Please answer to my questions separately, Question 1) So if I have two DNS severs, and ofc two IP address(81....
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2answers
108 views

Use of pool of addresses in source NAT

Source nat can be done using a pool of ip addresses. Suppose, I have a pool of 64 public ip addresses and I configure my nat enabled router so that whenever packets are sent outside, source nat all ...
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3answers
2k views

Cisco 1921 private LAN can't access internet on WAN interface

I have a Cisco 1921 Router with an private LAN interface, and a public WAN interface. I also have two VPN tunnels configured, one to another colo location and one to AWS. From the LAN side of this ...
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2answers
1k views

How are UDP source ports mapped on a NAT?

Here is an example use case; I am curious to see how this is suppose to work and why: Someone has a NAT router from their ISP. Behind the router are 2 PCs running Linux and using ntpd. ntpd sends ...
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24 views

Configure nat on src ip to dst port

I wondering about some workaround for issue that I have: I have 2 sources which generates multicast to 224.1.1.1 and port 12345. I'd like to configure on my Cisco IE 3000 NAT which will change the ...
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190 views

NAT overload and access to web resources

I have really bizarre problem in clients network. Clients have access to the internet via NAPT - I'm using several public ip addreses for this purpose. (I'll change ip addresses for obv reasons) ip ...
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3answers
439 views

How to configure NAT between 2 private network ? CISCO routers

If anyone can help with configurations it will be helpful
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3answers
385 views

Cisco IOS - dropping all traffic not translated by NAT

I have a couple of rather basic questions about NAT translation. For a simple translation like: ip nat inside source list ACL interface GigabitEthernet 0 overload If the traffic does not match ACL, ...
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1answer
148 views

Cisco NAT - Overload PAT and Static nat from one inside to two outside interfaces

i have following setup Cisco ISR4k Router with one inside LAN interface and two outside Interfaces. ---- WAN1 (NAT outside) LAN (NAT inside) -- ISR4k | ...
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How does 2 computers both behind NAT routers handle communication? [duplicate]

Currently reading up on TCP/IP protocol stack, while I was reading about the Network Interface layers, I started reading about NAT, and how it meant to decrease the amount of IPv4 used, by using the ...
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3answers
10k views

How to clear all static NAT entries with just one command?

I am using cisco 2901 Router with IOS version 15M. In the configuration of the router I am using lots of static NAT entries. And I need to change these entries when it is requested. And a possible ...
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1answer
70 views

Cisco IPsec VPN tunnel problem

I have a problem with VPN configuration. This is the topology I created: First updated licenses to make the VPN available: license boot module c1900 technology-package securityk9 IPsec Router ...
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1answer
205 views

Cisco, Router can communicate; hosts cannot

I am learning CCNA related tasks, I have picked up a Cisco 1900 Series router. I am attempting to set it up behind my existing router (Comcast standard router). My "Real" network is 10.0.0.0/...
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2answers
218 views

What risks to continue to use a legacy public network address in specific address/port NAT on a private network

Here is the background info: I support a legacy regional group of users with trunk mounted cellular data modems. These devices use a private APN, meaning they do not communicate directly over the ...
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4answers
137 views

Does a Business Router from an ISP perform actual routing or only Network Address Translation (NAT)?

Let's say that the professional business router is connected to the Internet through the WAN port and has some devices in the office connected through the other ports. The devices in the office ...
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4answers
3k views

How can multiple devices share an IP across the internet?

I do realize that most LANs sit behind a device running NAT, which translates the users private IP address to a public IP address. My question is still if you are trying to connect to a private device,...
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4answers
3k views

Port numbers and private IP addresses in Port Address Translation

Sorry for my limited knowledge in Networking. If I understand correctly port numbers are application level addresses for network communication, e.g. port no 20 is assigned for FTP. In PAT, we map ...
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2answers
1k views

Static NAT problem preventing internet access from LAN

Recently access outbound from all my LAN servers has stopped working. I have a 7206VXR running 12.3(4r)T3 which has a LAN interface using RFC 1918 IP addressing, and a WAN connection to our ISP using ...
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3answers
908 views

Cisco 1921 Sub interface access to internet

I have set up a sub interface on Gi0/1 and I would like to provide access to the internet for devices on the VLAN that routes to Gi0/1.200. The devices pick up DHCP addressing just fine but cannot ...
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1answer
120 views

Issue w/ Cisco router and failed NAT and static default route

I have a cisco router that is using a VRF to support a site to site VPN tunnel. I have added a second network to the router for non-VPN standard internet use. My problem is that my default static ...
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3answers
4k views

At which layer does router operate?

I have studied from various sources that router is a layer 3 device. It does routing based on Network layer (layer 3) header, but I have a doubt. Network address translation (NAT) is a feature of ...
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3answers
96 views

Do NAT devices need to have private IP addresses?

If a NAT's job is to create mappings between internal ip/port pairs and external ip/port pairs with one Internet-routable IP address, does a NAT need a private IP address for itself? I think one ...
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2answers
735 views

Slow performance with Cisco Comcast Business router with static IP address

20I have a server with a static IP address connected to a Comcast Business router (Cisco DPC3941B). I also have a second machine directly connected to the same router. It gets assigned a NAT address ...
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2answers
385 views

Juniper NetScreen NAT from a secondary Untrusted Zone

We have multiple public IP address subnets for various purposes. I need to create an Internal Zone behind NAT that presents itself as having an external IP in External Zone B. [...
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2answers
71 views

Is it possible to see the NAT or PAT mapping from the firewall logs?

Is it possible to see the NAT or PAT mapping from the firewall logs? For example a Fortigate. Thank you This is my previous question which I cannot edit. But here I am posting a precise question. ...
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2answers
2k views

NAT Translation Table Port Number

I had a practice question about a NAT-enabled router with outside address 24.34.112.235 and inside network 192.168.1/24 and three inside hosts .1, .2 and .3. The three hosts all open two connections ...
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310 views

Why does NAT keep track of each packet not just connections?

I have tried packet tracer and actual cisco routers and I find this weird: NAT uses different source ports, usually incrementally, for consecutive packets from the same connection. Why is that? ...
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3answers
4k views

How does NAT decide which connections are inbound, and which are outbound?

I'm building a P2P application that needs to be able to access nodes behind a NAT. This NAT does not allow inbound connections, therefore the nodes outside the network cannot reach out to the nodes ...
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6answers
4k views

Could IPv6 make NAT / port numbers redundant?

From what I can tell, each process could get its own IP address, with loads of IP's to spare. What would the drawbacks be? Essentially, your host would become a router and each process is a host (in ...
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1answer
51 views

NAT cannot communicate with 2 network

I have configured BGP for routing and NAT for HQ and Branch. I can ping from windows / server to public IP and also Linux Mint ping to public IP. but, I cannot ping / communicate between network HQ to ...
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3answers
1k views

routing between vlans not working

I need to put a Cisco router behind an ISP router. (The ISP doesn't allow us to use their modem only.) I've called the ISP technical service and they've set up the connection with me. Their router ...
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2answers
229 views

General: What is a dynamic gateway, how does it work, where is it used?

I saw this option in my OPNsense gateway configuration, and was hoping someone could shed light on what it is, exactly: Dynamic gateway policy: [YES/NO] This interface does not require an ...
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2answers
90 views

Network ( routing and switching) , security

In my company network i am installing new cisco2811 router but i have problem, my LAN network can not ping and access network. i get point to point internet from ISP. PTP IP is 192.186.86.200/24 and ...
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297 views

PAT not translating at all

I am studying for my CCENT. I threw together a PAT practice lab. Other than DHCP and RIP everything is pretty stock. No VLANs No security Just NAT overload on ACCESS router. I am stumped why it isn'...
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46 views

Need a little clarification with NAT and IPv6

I understand NAT exists to not exhaust all the ipv4 addresses so there is no need for it with ipv6. So with ipv6 having an unimaginable amount of addresses, will every device have its own public ...

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