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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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Full cone NAT in Kubernetes [closed]

Does anybody know how to achieve full cone NAT connectivity inside k8s pods? I've tested NAT on EC2 (without k8s): % pystun3 NAT Type: Full Cone Different story inside pods: % kubectl run natdisco --...
2 votes
2 answers
349 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....
0 votes
1 answer
895 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 | ...
2 votes
2 answers
338 views

Static NAT and PAT

I have two private IP addresses, want to make them NAT to 203.0.113.0/2 public IP address. WAY 1 : Static NAT (2 ip addresses NATted to one by manually) WAY 2 : PAT (Router gives port number ...
0 votes
2 answers
694 views

Cisco router on a stick with public ip wan (ISP)gateway

I am trying to create a router on a stick with an outside facing sub-interface with a public IP from an ISP. I have tried to configure NAT and routing but I just cant get to ping the internet. I'm ...
0 votes
1 answer
5k views

Destination NAT on Cisco ISR

I know how to perform regular overload PAT in my lab running sh ver Cisco IOS XE Software, Version 16.03.09 Cisco IOS Software [Denali], ISR Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 16.3.9, ...
0 votes
1 answer
56 views

Should a router behind the internet gateway run source NATing or masquerading if the gateway router is masquerading?

Edit: On a multi-router network, should a router (R2) behind the internet gateway (R1) run source NATing or masquerading if the gateway router is masquerading? At this time I can ssh from a host on ...
0 votes
1 answer
84 views

Why does EKS Fargate require NAT?

EKS Fargate is an AWS service for "serverless" hosting of some pods in a Kubernetes cluster. The docs mention that NAT is obligatory, why is this? I tried using traceroute from a Fargate pod....
-1 votes
1 answer
28 views

Router SNATs incoming connections [closed]

For some reason, my router changes the source IP of incoming connections. I can't find which setting makes this happen or if this expected behavior. For example, this connection was initiated by an ...
0 votes
1 answer
110 views

Problems with twice-NAT on Cisco 3548

I'm trying to get Twice-NAT working on a Cisco 3548 switch. I have a VRF set up with 2 L3 ports on it - Eth1/33 has ip address 20.20.255.250/16 and is nat inside Eth1/34 has ip address 10.10.1.211/24 ...
1 vote
1 answer
247 views

Communication between hosts on different local networks

I understand how NAT works in case of communication between one, local host and a server with specific public IP address. The host is sending a request, it pushes the packet with destination IP ...
0 votes
1 answer
32 views

Router cannot access LAN with public IP [duplicate]

I have the following setup: ISP | | external interface (public ip) / Router (running OPNsense) \ internal interface 192.168.0.1 ...
0 votes
1 answer
219 views

How localhost and its opposite 0.0.0.0 works

Here I am running an application on a computer, host=localhost, the application runs on localhost:5000, or 127.0.0.1:5000. When the computer accesses 127.0.0.0/8, or 127.0.0.0 subnet mask 255.0.0.0, ...
3 votes
2 answers
128 views

Is NAT66 really not used when there are all these apps exposed by public load balancers?

I am imagining a Kubernetes IPv6 based cluster with Nodes in a private subnet and an Ingress deployed that sets up an application load balancer in a public subnet which receives a public IPv6. You can ...
8 votes
5 answers
3k views

PAT and Static NAT not working together?

The HQ network is using PAT to gain access to the internet, the internal webserver needs to be accessed from the internet using static NAT. Configs: S_HQ ! interface FastEthernet0/1 switchport ...
3 votes
1 answer
148 views

NAT takes me to a wrong place

We have a 5555-x with multiple interfaces. Our Outside interface and DMZ interfaces have routable IP addresses and DMZ subnet is routed via IP address of the outside interface. Stripped for ...
3 votes
1 answer
581 views

Cisco ASA static nat one-to-many from interface address to object-group

Syntactically, the following set of statements is valid (at least as of 8.3): interface Ethernet0/0 nameif OUTSIDE ip address 192.0.2.1 255.255.255.0 interface Ethernet0/1 nameif INSIDE ip ...
1 vote
1 answer
52 views

Nested Network with same IP Space

I have a router (Teltonika RUT) that is connected via its WAN port to a network (let's call it "Big"). The IP Space of the "Big" Network is 192.168.1.0/24 with the Gateway on 192....
1 vote
0 answers
14 views

Firewall not reverse translating NAT address in VyOS GNS3

I'm using two VyOS images as Firewalls in gns3, to which I have connected two routers, one from an inside network and another from an outside network. I configured NAT in both for the internal ...
8 votes
2 answers
1k views

How does UDP NAT Know When To Remove The Rule

So say you are a user behind a NAT/router on an internal network. You begin sending UDP data to an internet-facing server. The packet hits your router, it inserts an entry to allow returning packets ...
0 votes
1 answer
265 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 ...
0 votes
1 answer
164 views

Problem with Configuring Selective DNAT for HTTP Traffic on Fortigate Firewall

I'm currently in the process of setting up a new Fortigate Firewall and have run into an issue while configuring DNAT. From what I understand, this is done through Virtual IPs in Fortigate. My goal is ...
0 votes
0 answers
13 views

Where is 1.1.1.1 really located? [duplicate]

I'm courious how this works: When ping-ing 1.1.1.1 I get results of roundabout 15 ms, where 1.1.1.1 is located in California, according to iplocation.net. When ping-ing a random ISP from California I ...
0 votes
1 answer
46 views

Hosts behind PAT not able to communicate with each other

Suppose I have the following network layout, with two routers connected directly, with Port Address Translation (PAT) setup on both of them. The first router labelled Router PAT 1 have been configured ...
1 vote
4 answers
648 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, ...
0 votes
1 answer
47 views

conntrack expectation on directed broadcast [closed]

I'm testing out a setup that I would reproduce in a production environment if I get it work. What I have: A wireless network 192.168.88.0/24 An IoT device X in the wireless network A Teltonika router ...
2 votes
1 answer
1k views

Is NAT hole punching feasible, when the external source port of NAT changed for different destination?

I have a question about hole punching. A-Client B-Client S-Rendezvous server Both A and B connects to S. S learns the random NAT ports of clients. Then sends the IP/Port info to clients. Clients ...
8 votes
2 answers
2k views

UDP hole punching when NAT port distinguished for every outgoing UDP connection?

I just read an article about the process of "punching holes" with the UDP protocol. I understand how it's done, but I have one last question to clear up things. We have the rendezvous server and ...
3 votes
0 answers
259 views

Router as PPPOE concentrator, PPPOE clients unable to get to DMZed static NAT server

I've been trying to figure out this problem, and I'm just not up to the task. I have a Cisco 2911 router as follows: Internet connection on GigabitEthernet0/1. Which has it's own static IP: A.B.C.38/...
0 votes
2 answers
94 views

How to connect TCP server behind NAT

I need to establish TCP connection with a server located behind the NAT. The simple solution is to reverse the connection and ask the server to connect to the client, but then I am unable to use ...
9 votes
5 answers
13k views

Why does NAT translate a source port?

I’m beginning to learn about NAT and I was wondering: Why does NAT translate a source port? Doesn’t a port represent an application that’s requesting a service? So why must it be translated? Also what ...
0 votes
0 answers
438 views

Simultaneous dynamic and static NAT not working

Cisco 4200 series running IOS XE with a single public IP address and dynamic NAT, which works just fine. I am trying to add Static NAT to access a server (map external port XX to internal port YY. ...
0 votes
0 answers
105 views

Clarification of external interface vs source interface filter in Fortigate DNAT/VIP

On a Fortigate firewall, one can configure Destination NAT using the DNAT & Virtual IPs section of the GUI, or the config firewall vip section of the CLI. When you create a DNAT object using ...
0 votes
1 answer
279 views

How to remote access CCTV's device behind CGNAT for IPv4, and device doesn't have support for DDNS IPv6? [closed]

TL;DR Multiple locations with local CCTV. How to remote access all of them, with an ISP that services IPv4 behind CGNAT and the DVR doesn't supports DDNS for IPv6. DVR also offers API, SDK, P2P and ...
1 vote
1 answer
85 views

Why can't we use large-scale NAT system with thousands of private IP addresses assigned to a single public IP

Instead of assigning everyone an individual public IP address, could we use a very strong NAT system with thousands of private IPs behind a single public IP? This could reduce public IP demand and ...
0 votes
1 answer
529 views

IP masquerading and NAT

What is the difference between IP masquerading and NAT? Do both of them have the same limitation? Does the statement "IP masquerading cannot provide full internet connections to the hosts which ...
9 votes
4 answers
6k views

Does IPv6 remove the need for a VPN?

I know that a VPN may be used in lots of different ways for lots of different things, so I'm not suggesting that IPv6 removes the need for a VPN completely. I'm interested in one particular use-case: ...
0 votes
2 answers
253 views

How to apply a Route-Map to a NAT connection

I am following a tutorial about route-maps on youtube. https://www.youtube.com/watch?v=2YlsXcT1Pjw There is this topology. The default route on R1 points to 10.10.10.2 In the video he just shows how ...
0 votes
1 answer
50 views

2 Routers for PPPoE and NAT 5 Public IP [closed]

My ISP have provided me with 5 Public IPs. I tried to NAT these 5 IPs to our local server by using this setup. The primary router will be setup for the internet connection while the one-to-one NAT of ...
9 votes
2 answers
13k views

NAT and UDP problems

I have a question regarding NAT, UDP and TCP. Given a standard NAT server, is it a problem for it that UDP is connectionless? If so, why? And does TCP or QUIC solve this problem?
1 vote
3 answers
693 views

Can a host in a public network communicate with a host in a private network, by layer 3 alone?

Suppose a private network and a public network are connected by a router or some other device. After a host in the private network sends a message (e.g. a HTTP request) to a host in the public ...
0 votes
2 answers
120 views

Communicating to a device with a random IP, Subnet Mask and Gateway

I think am looking for a way to reliably communicate with devices connected to the network with "wrong" configurations. Our company sells products that can have their network settings ...
1 vote
1 answer
640 views

How to use 5 static ip addresses with virgin media broad band

I have installed virgin media business broadband and the package comes with 5 static ips. These IP are GRE tunnels from the HITRON router to virgin. the IP addresses are for example 66.66.66.65 - 66....
0 votes
1 answer
44 views

Simple question about NAT [duplicate]

So I am learning about NAT. I understand that it changes IP from public>private and vice versa. From my understanding, when a packet or info gets sent to the public ip towards the private ip, ...
1 vote
0 answers
165 views

How to forward UDP unicast messages to multiple destinations [closed]

I am trying to forward a UDP Unicast message so that it cant be received by multiple computers. Can anyone point me in the right direction for how to accomplish this? Here are the details: There are ...
0 votes
1 answer
89 views

Is internal network traffic sent to private subnets via their NAT Server?

Similar to this question, I'm wondering how resources in my public subnets communicate with those in my private subnets - when there is a NAT service present. My impression is that a self-managed NAT ...
19 votes
6 answers
42k views

IPv4 Segment 100.64.0.0/10

I recently got to know that IP segment 100.64.0.0/10 has been reserved by IANA for 'Shared Address Space'. My question is: Can I use the IP Segment 100.64.0.0/10 as a private range in my network (...
4 votes
4 answers
1k views

Is a gateway both a router and a NAT?

From Tanenbaum's Computer Networks: The general name for a machine that makes a connection between two or more networks and provides the necessary translation, both in terms of hardware and ...
0 votes
1 answer
91 views

NAT configuration behind pppoe with virtual server

my CISCO 3925 router is handling pppoe, NAT, and DHCP server.. My local LAN is 192.168.1.x and it's behind that NAT. I'm trying to enable access to a DNS server that's on this LAN (192.168.1.191 tcp/...
0 votes
3 answers
450 views

Can I use the network and broadcast IP addresses of a /24 subnet, when the /24 subnet is included in a larger /22 subnet range for NAT?

I'm wondering if I can use the network and broadcast IP addresses of a /24 subnet, when the /24 subnet is included in a larger /22 subnet range for NAT? PS: Please consider that 198.51.0.0/22 is ...

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