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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Configuring the NAT 1:1 rules with pfsense

I have two pfsense. One pfsense is on 192.168.0.1 and another pfsense is on 192.168.20.1. Basically I have installed 20.1 pfsense on one machine 192.168.0.180 which is in the network of 0.1 pfsense, ...
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1answer
49 views

Why specify additional NAT rule

In watchguard's guide for NAT loopback when describing the additional nat rules required, they show this image: Why are those top two NAT rules necessary, ie aren't they already covered by the next ...
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2answers
155 views

IPSec - NAT-T inner/outer IP of the gateway?

I was configuring an IPSec VPN and somehow I can't figure out what the inner/outer IP of my gateway would be. Have a look at this image : Imagine I have my site-to-site VPN, with my gateway having ...
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1answer
68 views

Discovering public ip from wifi signals, shodan, parent router NAT [closed]

MAC addresses innately do not change right? and you're able to scan for broadcasting APs where you'll be able to detect different nearby mac addresses of each AP.. Public IP addresses change, ...
2
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1answer
109 views

Asa5508 NAT two internal IPs

Hello I have a Cisco asa5508 and I want to NAT 2 internal IP's to 2 public IP's that I have.Each IP on its own. Currently I have NatPool and it's working either with the one IP or with the other. Is ...
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1answer
126 views

Is NATing possible in case of IPV6 addressing mode anyway?

Setup: A(2001::1:123) <------> B(2001::1:124) <------> C(2001::1:125) where A,B and C are the systems.And apply rule of NAT(SNAT/DNAT) on system B for forwarding a packets from C to B,B to C,A ...
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4answers
17k views

What is the difference between DHCP and NAT?

Both seem the same to me. I don't see how DHCP is different from Dynamic NAT. Can anyone please help?
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1answer
163 views

2 Wan DHCP to cisco router

I have a cisco 2921 router and 2 wan ips provide by 2 diferents isp via dhcp. The main connection is funtional right now, I have a subnet with a nat to this ip, but I want put the second ip just to ...
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1answer
597 views

ASA VPN Tunnel NAT Issues

I've been trying to jump through two tunnel. A Customer has a cloud solution which we need access to. Since we already have a vpn site2site tunnel to the customer we can already access his LAN. What ...
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2answers
311 views

How does/did an ISP serve so many people over IPv4

Whilst reading Tanenbaum - Computer Networks they talk about IP scarcity at the level of ISPs: IP addresses are scarce. An ISP might have a /16 address, giving it 65,534 usable host numbers. If it ...
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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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1answer
196 views

Can a host behind a basic NAT visit two services on a server at the same time?

When reading Data Communications and Network (5th edition) by Behrouz A. Forouzan, I have trouble with the explanation for NAT. On page 546, the book describes a modifying-IP-only NAT (a.k.a. basic ...
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1answer
131 views

HP MSR2004 router is not processing udp through nat

I set up a new HP MSR2004 router for a corporate network. The network uses an internal private net and has one static public ip address. Surfing the web and all tcp related things seem to work fine. ...
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1answer
1k views

Bridging networks without NAT: how it's done?

I have quite limited networking experience, so probably i'm asking about very simple things. I'm reading about linux bridge interfaces, and documentation states that there is no NAT by default and ...
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2answers
737 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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0answers
136 views

Cisco: Routing issue between LANs [closed]

We have a project to create 3 offices, which are 3 different LANs where the configuration should be as follows: Each Office should have 1 printer, where the office is able to print They should be ...
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4answers
313 views

Access a subnet through another network [closed]

We have some devices connected together through a switch. We need to access them through another network, but because of limitations in available IP addresses, we can't get an IP address from that ...
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1answer
308 views

Is an ACL needed when using PAT (dynamic nat)?

We have a single router (4331) that connects to our ISP. We do PAT (dynamic nat) to give users internet access. Now typically we'd have an OUTSIDE-IN ACL that blocks traffic from the internet. My ...
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4answers
371 views

How does the router tell if a packet is sent to local host or public host

I might sound silly, but I'm beginner. If there are two hosts with the same IP but one is public and the other is private. If I send a packet to that IP. Will it be forwarded to the local host on my ...
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1answer
124 views

IPv6 VPNs source address selection

Say I have the following IPv6 prefix assigned to me by my ISP : 2a01:1000:1000::/48 with 2a01:1000:1000::1/48 assigned to my VPN server. I set up a VPN with a /64 from that block to assign to my ...
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1answer
842 views

How is CIDR Used Today with the Introduction of NAT?

I'm new to networking and trying to understand how CIDR is still relevant with the introduction of NAT. If we have a public/private scheme for routers, how is CIDR still relevant? Is this at an ISP ...
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2answers
530 views

What provision does DS-Lite, as used by ISPs, have to provide IPv4 blocks to CPE?

I run a small ISP for a rural community in England. There are around 350 residential properties and 15 small businesses. Three of these businesses run systems that require two consecutive IPv4 ...
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1answer
129 views

Configuring Cisco ISR 1861 with External Cable Modem

I picked up an 1861 for cheap and I am trying to set it up for home lab. I have taken the Cisco courses for CCNP and I think if this was just a regular router or switch I would be OK, but I can't ...
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3answers
913 views

Translate between multicast addresses

I have an application with a bug that does not recognize a certain multicast address as valid. It's an address used by another system i don't have control over, and these two systems communicate via ...
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2answers
2k views

How do ISPs configure a static ip in a double nat? [closed]

So I have an ISP which I requested a static ip. My ISP gives a static ip for a one time payment. So I decided to get one. My ISP does double NAT which by default all incoming tcp ports are blocked. ...
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1answer
385 views

Accessing Servers behind double NAT [closed]

Basically, I want to know every possible way to access Linux servers or any other devices located behind ISP'S (Carrier-grade NAT) and our local NAT. I have used VPN and forward-reverse tunneling ...
2
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2answers
954 views

ASA cannot ping outside through NAT on border router

I have the following topology below, in GNS3. Basically, the cloud NAT-1 is the Internet, R1 is my border router with NAT and FWASAv-1 was supposed to be able to access the Internet, but can't. I ...
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1answer
701 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 ...
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1answer
1k views

Should DHCP relay and destination NAT work together?

Topology: [PC1]---lan----[RT1 / DHCP relay / DNAT]---wan---[DHCP server] [PC2]---------/ / [PC3]----------/ DHCP relay makes the a DHCP broadcast into a unicast and Forwards it to the DHCP server ...
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1answer
245 views

What Is Session Border Controller [closed]

What is Session Border Controller(SBC). And What is the Advantages of SBC. How Does It Works?
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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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1answer
2k views

How does NAT Stitching work?

While reading about CISCO NetFlow Analysis I came up with a term named NAT Stitching. I understand Flow Stitching which join same type of inbound and outbound connection. But can't find anything ...
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1answer
300 views

Translation from unique local to global unicast address

is there NAT in IPv6 for private-to-public translation like in IPv4. I know that there is a protocol translation between v4 and v6 but did not find anything about same protocol translation . Thank ...
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1answer
2k views

1-1 NAT on a SonicWall with a DMZ

A new PBX is being installed at one of our clients today, and they have requested that we give them one of our unused public IP addresses(Comcast is the ISP, have a block of IPs) for use with the PBX. ...
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2answers
787 views

How does NAT table response when there are no open ports?

I'll be glad to hear what really happens if the router has no open ports, for example if there is a big network and every computer sent a lot of requests and the server is slow so the table's ports ...
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1answer
169 views

Were private IP ranges used publicly before inception of NAT?

I know NAT was developed to solve the problem of IPv4 address exhaustion. I am not very familiar with the history of how the Internet evolved (except ARPAnet because that is in every networking book). ...
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2answers
711 views

How to assign a second available Public ip for NAT (Dynamic PAT) to Inside Network Cisco ASA 5516-X

I have a x.x.x.200/29 subnet of Public IPs. Router Interface: x.x.x.206 255.255.255.248 ASA 5516-x outside: x.x.x.201 255.255.255.248 ASA 5516-x Inside: 10.111.22.254 255.255.255.0 I want to nat ...
2
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2answers
198 views

UDP packets vs two parallel gateways running NAT

I‘m writing an application that sends information, using UDP packets, to the server on the internet and then receives data same way. It seems to work fine from behind NAT but I’m wondering about more ...
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1answer
524 views

PBR not working as expected

EDITED: ADDED FULL ROUTER CONFIG I have a cisco 2921. It uses EIGRP to learn its routing table and has no static default routes set up. I would like to keep it that way. The default route (learned ...
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1answer
2k views

NAT device on L3 Switch

This is our current network topology. Everything works fine, but I have some concerns about it. I'm questioning myself about the following, and would like to improve what we current have. The two (...
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2answers
7k 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?
3
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1answer
606 views

NAT inside destination not initiating

This lab is done on Dynamips, and the setting is like below: There are two identical servers(192.168.48.74, 75) inside NAT, and the servers will use one public IP 200.200.17.34/29. R1 is the NAT ...
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2answers
352 views

Cisco IPSEC Tunnel with hidden local networks

I've got an ipsec tunnel that's up and working with ATT. They require that the phase 2 IP's not be local LAN's, but public IP's. So, my phase 1 is X.X.X.132, and my Phase 2 is on the same subnet as X....
1
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1answer
486 views

SonicWall Site-to-site VPN with WAN IP endpoint

I'm not a real network engineer (just something I must dabble in from time to time), so hopefully I will provide enough detail and use the right terminology here. We have a site-to-site VPN ...
9
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2answers
2k views

Is there anything stopping me from using Class A addresses on my own network?

I've been reading about IPv4, networking, subnetting and the different classes of addresses. I understand that IP addresses beginning with numbers from 1 to 126 are considered "Class A" addresses. ...
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0answers
161 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/...
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2answers
359 views

CGN and its advantages

I have been reading about CGN. Though similar to NAT it is used by service providers to route traffic without the need for the a public IP address. But when the packet leaves the ISP to the public ...
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5answers
7k 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 ...
2
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2answers
542 views

Natted client cant ping default gateway

I have a Cisco ASA 5506-x Firewall that I am using to NAT addresses on a machine subnet. These addresses are from a VLAN. When I ping from a 192(Subnet) address to a 177(Vlan)address through the NAT ...
2
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2answers
160 views

Is it possible to use NAT/PAT with hosts on the inside acting as servers to the outside?

Let's say that the public address of a NAT router is 200.1.1.2, and on the inside there are three hosts with private addresses 10.1.1.1, 10.1.1.2, and 10.1.1.3 resp. acting as servers. If a HTML-...

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