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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Does NAT always translate the destination address of a packet?

From https://www.cisco.com/c/en/us/support/docs/ip/network-address-translation-nat/13770-1.html This document provides a sample configuration with the ip nat outside source list command, and ...
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1answer
115 views

Without NAT or NAP, can a host in the Internet send a response back to a host in a private network? [duplicate]

Suppose a router device connect a private network and the Internet, and doesn't have NAT or NAPT features. If some application on a host inside the private network sends some packets to a host in ...
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3answers
239 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 ...
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282 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. ...
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1answer
419 views

Juniper SRX Destination NAT for L2TP server

I have a L2TP server on my LAN which I would like to access from WAN and there is a Juniper SRX standing between these two networks. I've had some success with this post: https://forums.juniper.net/t5/...
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2answers
251 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 ...
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2answers
142 views

What are the differences between packet forwarding and network address translation in layer 3?

What are the differences between packet forwarding and network address translation in layer 3? Is packet forwarding done by a router between two networks that use public IP addresses? Is network ...
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2answers
962 views

Unable to access Server over VPN behind 2 Fortigate Firewalls; however ping is working

Client -> VPN -> FG1 -> FG2 -> Server Created a VPN tunnel with remote IP 10.20.30.4/32 and local ip 10.20.30.40/32 on FG1, NAT/VIP is established with VIP as 10.20.30.40 and server IP as 192.168.2.6 ...
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2answers
190 views

Are both VPN and NAT alternative ways to provide access to a private network?

https://en.wikipedia.org/wiki/Virtual_private_network A virtual private network (VPN) extends a private network across a public network, and enables users to send and receive data across shared or ...
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1answer
1k views

How do i find out if a LAN is behind a multi-level NAT? [closed]

Not much i can specify here - its obvious that my CPE is NATing my LAN, but how do i find out if my ISP is using a carrier-grade NAT (obviously, without asking them)? I heard that port forwarding is ...
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1answer
64 views

MAc address or IP address? which one gets used from my pc to router? [duplicate]

Question 1) which one is used nowadays? NAT or PAT? Question 2) as I knew, when my pc requests some website, what happens is , the data(packets) from my pc go to router. then router makes the request ...
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1answer
47 views

How do I find out which NAT is getting hit?

I can see in packet captures that my packet's destination IP is getting translated. How do I find which NAT statement is responsible for the conversion if my device has over 200 NAT rules? I'm using ...
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1answer
77 views

How does packet traversal works over a public network with NAT overloading

Let's say I have a private network connected to the internet with default gateway 192.168.1.1 on Router1. Now a host(Host#1, 192.168.1.10) on this network wants to send a packet over the public ...
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2answers
162 views

How can AWS restrict access by private IP?

The official AWS docs state: If you are connecting through an ISP or from behind your firewall without a static IP address, you need to find out the range of IP addresses used by client ...
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0answers
108 views

Cisco L2TP Tunnel and NAT

I have problems with NAT clients connected to an AP . This AP has an L2TP tunnel established to a Cisco router (7206VXR). The session is UP and the router can ping the IP of the client. The client ...
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0answers
754 views

Why NAT type detected by `stun` command depends on used STUN server? [closed]

# stun -v stun.counterpath.net |& grep '^MappedAddress\|Primary' MappedAddress = 93.84.76.218:20458 MappedAddress = 93.84.76.218:20458 Primary: Independent Mapping, Port Dependent Filter, preserves ...
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2answers
231 views

Accessing internal website from subnet

I have the following network: - Edge Lite 3 router with public IP on WAN (eth0) and 2 LANs: 1) eth1 192.168.1.11/24 2) eth2 192.168.2.11/24 eth1 is DHCP, I have several work laptops inside. eth2 ...
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1answer
95 views

A question on NAT [closed]

I know ISP's use NAT to provide a home user with a public IP. If multiple devices connect to the internet using the same router all will have different private IP addresses but similar public IP ...
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1answer
57 views

Daisy chaining IOT devices without switches? [closed]

I have multiple IoT board with two network interface in each device. I want to connect them in a daisy chain without help of switch. The eth1 of first device will be connected to eth0 of second device,...
4
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1answer
343 views

Will the data transfer with the destination on the same LAN network be routed through the internet when the WAN IP is used?

I'm planning to set up a Nextcloud locally. I will be using my own domain with a DNS record to connect to my WAN IP and port forward the needed ports to the local machine running Nextcloud. Now of ...
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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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4answers
850 views

Can I make 2 ISP providers' IP addresses into 1 IP address?

We have 2 ISP providers (X, Y) and we have connected the ISPs to a core switch>Sophos firewall>Switch rack>end user (LAN & WiFi). This ISP works on fail-over mechanism. The issue here is that we ...
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2answers
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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1answer
624 views

Source NAT on Juniper SRX300

I'm having issues setting up the Source NAT on my SRX300 firewall. The firewall is connected to an LC-panel through a fibre optic cable in port 0/6. I have set the public ip on that interface and have ...
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2answers
83 views

How could a response be sent to the requestor without requestor's address?

I'm reading this talking about the differences between two fire-and-forget message (for example, under UDP) and a request-response communication (for example, under TCP). I came across this: The ...
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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
328 views

How to run SIP phones in the LAN (NAT Overloaded to single IP)?

We have a small office network switch connected to a DSL modem for internet and telephony access. Now we would to extend network to another location in the same building for which I deployed a cisco ...
2
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1answer
2k views

Can VPN on router connected to the modem bypass a double NAT created by two routers unbridged and connected to each other?

I can't seem to get my head around this scenario. If I am right, a VPN configured on the client-side/workstation would definitely bypass double NAT but on this scenario: Modem <-bridged-> Router ...
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0answers
430 views

Cisco - Change both source and destination on NAT [closed]

Note: As usual I'm dealing with single device so there are limits on what I can change outside of this router. Device: Cisco 1841 IOS: 12.4(13a) Vlan1 - IP: 192.168.0.3 Vlan1 (Default Gateway): 192....
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1answer
1k views

NAT VLANs with same IP Subnets

I have a VMware environment in which VMs are running a simulation suite. The software used has hardcoded IP addresses, about 10-15 VMs, and we are running multiple instances of this software each in ...
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7answers
19k views

Why are IPv4 addresses running out?

I understand that we are running out (or ran out already?) of IPv4 addresses, but I don't really understand why that is. Right now, every home has its own IPv4 address (dynamically assigned, but still,...
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1answer
59 views

Cisco IOS 12.3 - Mysterious NAT - Where is it defined?

I have the following config (IOS 12.3): A.B.C.13 stands for the outside, public IP, bound on interface Fa0/1.52 37.247.X.206 is a public client I am using to test x.x.x.n stands for a random public ...
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1answer
42 views

Does the VM under the NAT network can contact the dedicated servers? [closed]

I have bellow snapshot's network configration: in the Dedicated Control Server(172.18.1.249) there is a VMware VM1 with ip 172.18.1.247, and it use the NAT network(gateway is 172.18.1.248). I want ...
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1answer
2k views

Port-forwarding rule on Cisco ASA not working - “Drop-reason: (acl-drop) Flow is denied by configured rule”

New to Cisco, so I hope this question isn't too noobish. I am trying to setup a port-forwarding rule to allow "any" SSL traffic in from "Outside" to the web server on my LAN. The problem is apparently ...
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1answer
422 views

ASDM access broken on Cisco ASA 5505 - NAT rule gone wrong

I was trying to setup NAT and Access Rules and apparently did something very wrong because now I cannot get into ASDM at all. I've tried multiple machines and all of them time out. Also the landing ...
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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 ...
2
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1answer
342 views

Firewall Rule 'Both Ways'

I'd like to think I have a good understanding of NAT and Firewall rules at a basic level, though please correct me if I'm wrong at any point. I've seen many products list their firewall requirements ...
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1answer
306 views

Is an SBC sufficient and can it NAT

We have a gateway which faces out to our VoIP SP. As we get more users we need some security in front of it. Currently our gateway terminates directly to the SP. We would like to put a SBC in front ...
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6answers
2k views

Why is classful addressing considered waste?

I am trying to understand the addressing strategies. But there is something which I can't grasp. Maybe I am missing a very basic point, if so, I am sorry beforehand. From my researches, let's say, if ...
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0answers
722 views

pfsense Server Load-balancing on LAN Interface [closed]

I am trying to load balance a couple of web servers from the LAN side as I don't need access from the WAN so that clients on the LAN can access these web servers: LAN IP is 192.168.10.1 I created a ...
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2answers
3k views

How does NAT work with incoming UDP packets from unknown IP

Apologies in advance for the relatively noob question and if this is off topic here ( I am not sure...) The situation is that I have a UDP client and server bound to the same port. My understanding ...
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1answer
140 views

Outbound NAT for single host behind an ASA located over an IPSEC tunnel [closed]

I have these two nets connected over the public internet with ASA 5510s. 192.168.0.0 < -- ASA1 ---> Internet <--- ASA2 --> 192.168.5.0 Each net does either a simple dynamic or static nat ...
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2answers
760 views

Leak default route to multiple VRFs while keeping VRFs isolated from each other

I'm working on a configuring stuff on a Cisco Nexus 3k based platform and trying to isolate different things into different VRFs which should not be able to talk to each other. Some of these VRFs ...
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1answer
61 views

Connect office to multiple customer VPNs

First time post here so if this is off topic please let me know where to ask this question. A company that provides outsource billing services to multiple client companies using VPNs to each remote ...
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2answers
309 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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2answers
112 views

How does the NAT work [closed]

I have a public ip assigned by isp, two phones are connect to wifi router. In both the phones i am seeing news feed on different facebook accounts, so facebook gets packets from only one publuc ip ...
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3answers
588 views

Why can't a host B act as a server, and accept TCP connections, when sitting behind a NAT?

Originally, I thought I intuitively understood why B can't accept TCP connections, however when I read about how P2P applications circumvent this exact problem by using an intermediate peer that is ...
2
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3answers
4k views

Why to use public IP addresses within private networks?

I have started to work in a multinational company which has a global network spanning across 4 continents (20 0000+ network devices). I noticed that a lot of end user devices (PCs, laptops) have IP ...
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2answers
221 views

What is the point of outside NAT?

I understand how outside NAT works, but I do not know when it should be implemented? Could you please tell me some scenarios when outside NAT is needed? Thanks!
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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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