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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How does a router a layer 3 device translate port address in PAT, as it is a layer 3 device?

While I was reading about PAT i.e Port Address Translation.The router was configured to translate all the private IP addresses to one single public IP.Since router is a layer-3 device, it can do that ...
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2answers
3k views

Does NAT address need to be the default gateway?

I will use a firewall for NAT. The firewall will be part of a VLAN and will translate a machine network IP address for domain access requests. Should I set the devices on the network to use the ...
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1answer
249 views

ASA 5506-X as NAT only

We have a spare ASA 5506-X that we want to use as a NAT. It will be placed between a VLAN and a machine network. Is it possible to setup the device using only the wizard for this functionality. (I ...
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1answer
8k views

How `UDP Hole Punching` Works?

Can anyone explain how UDP hole punching works in a simple way? I know how NAT and PAT works, but can't get a clear idea about UDP hole punching.
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1answer
514 views

Trouble routing SSH traffic from internet to private server via VPN - Sonicwall to Draytek

Our small business uses a Sonciwall TZ210 on a fixed IP line in our office, subnet for this location is 192.168.3.0. This is connected to a Draytek 2850 router at my home address using an IPSec VPN ...
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2answers
473 views

Internal NAT before establishing a VPN Host-to-Host

We are establishing a host-to-host VPN with our business partner. After we exchanged our IP information they said that our LAN IP range will overlap their LAN IP range and we had to do an internal NAT....
2
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1answer
267 views

Proper network design for office use

I have two 4G LTE router modems in my office which we want our clients connect to these modems to have access to the internet. I have a shared server which should connect to these both modems that ...
2
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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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1answer
550 views

Cisco ASA not routing without identity NAT?

As I was writing this down I think the solution came to me. As usual. I'll write this down nevertheless to make the world a better place. =D Let's take a look at this beauty of a network ...
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1answer
302 views

Cisco Router, Port Forwarding, ACL ordering

I'm new CCNA learner here. If I have the following access list: access-list 101 permit ip 10.10.0.0 0.0.255.255 any access-list 101 deny tcp host 10.10.0.1 eq 443 any access-list 101 deny tcp host ...
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2answers
290 views

Why subnetting is implemented if we can use Network Address Translation (NAT)

As in subnetting a block of IP adresses are allocated, which leads to consumption of those IP addresses. Then how come we don't use Network Address Translation (NAT) as it will only need one IP ...
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1answer
86 views

Why is my Cisco MMS891 assigning IP addresses with static NAT entries to devices via DHCP?

I have a Cisco MMS891 ISR as my edge router with several static NAT entries, which are set up to NAT my LAN IP addresses (which are statically assigned to printers) to access an externally hosted ...
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1answer
828 views

PC cannot ping each other when using BGP

I am confused about why PC-A cannot ping PC-B. When pinging PC-B from PC-A, it is always time out, according to tracert, the packet stops at R3 g0/1. But I think according to the route table, PC-A ...
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2answers
6k views

pfSense IPv6 NAT

I know many of you said that IPv6 has no NAT, but my server provider told me, that it is possible. I have no idea how... I have a pfSense Server as my Firewall (Not the router!). I have a /28 IPv4 ...
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1answer
122 views

Unsecured devices and IPv6

I'm currently starting to read up on IPv6, and as soon as I heared that every device can/will have a public accessible adreess i got a little freaked out. There are a lot of horror stories about ...
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2answers
1k views

NAT on outside interface alternatives

I am struggling to configure some Cisco routers with NAT out of multiple outside interfaces. The interfaces are considered as alternatives: use the first one that works. Question: what's the ...
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2answers
588 views

NAT simultaneous tcp connection Open

I am trying to understand how the NAT behaves when two peers behind two NATs with two different public ip Addresses try to establish a TCP connection using simultaneous open. I did some research and ...
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3answers
1k views

Confusion regarding Port number

I may sound silly but I seem to be getting confused with what port numbers are used for. Someplace it's mentioned that port addresses are used for port translation using pat which i get. Somewhere it'...
4
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2answers
2k views

Problem with Cisco ASA 5510 DMZ configuration

I need help to resolve this issue. I have a Cisco ASA 5510 and I’m trying access to my webserver from internet but the connection does not work. Please find the network diagram below: I applied this ...
5
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2answers
933 views

Are there any transport layer protocol without the concept of port?

Are there any transport layer protocol that does not have the concept of ports? If so what do they use instead? Also how does NAT work for such protocols?
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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
284 views

ASA - No internet on NAT'd computers only

ASA5510 without any extra services such as utm and using Comcast business internet. Users stopped getting emails in middle of the night. That was our first indication. After checking things every ...
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2answers
2k views

How can I share my printer on different NAT? [closed]

Hello I am facing a problem. Here I am attaching an image file where my problem diagram is drawn. Please look at the image before read this problem. There you will get a clear view about the problem. ...
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2answers
177 views

Understanding NATting and PATing. How do routers actually forward packets? [duplicate]

I seem to get different answers from different people depending on the topic at hand. I'd like to actually understand how routers forward traffic to external networks using a single IP Address. I'm ...
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3answers
625 views

Cisco NAT of Source and Destination Addresses

I thought I had a relatively simple question, however I can't seem to find a solution online easily. My problem is: I have two Cisco 1941 routers configured each with their own direct internet facing ...
2
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1answer
336 views

GNS3 nat configuration issue

I'm studying for my CCENT exam, and I'm trying to practice configuration of the NAT. R1 configuration: Building configuration... Current configuration : 1211 bytes ! version 12.4 service timestamps ...
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4answers
724 views

Is there a valid scenario where a router is used to translate a public IP address?

NAT typically refers to router translating an IP address from a private network to a public IP address so that the node on the private network can access public Internet. Is there a valid scenario ...
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1answer
1k views

Simple networking behind a router without NAT and DHCP

I am novice to network engineering. I have two questions : Is it possible to assign a fixed public Ip address to a pc directly connected to a router without a dhcp and a NAT and having access to ...
2
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1answer
693 views

How to prevent IOS sending icmp unreachable with output ACL?

I have an output ACL applied on a WAN interface that permits only 1 IP from going out. interface Cellular0 ip address negotiate ip access-group allow100.98.170.25 out ip nat outside no ip ...
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1answer
388 views

Does an EIM-NAT work across both UDP and TCP?

I've read RFC 4787, 5382 and 5128 and I just need a bit of clarification. Assume a NAT has Endpoint Independent Mapping behavior for both UDP and TCP. Although I understand that if a machine would ...
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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
447 views

Does NAPT reuse already translated ports?

(Addresses and ports randomly made up for the sake of example) Suppose we have a machine and it's private IP address is 192.168.1.10. Suppose the machine's router's public internet IP address is 100....
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1answer
72 views

Does NAPT track the outgoing packet protocol?

If a machine sends a UDP packet to some destination over the internet, and that destination sends a packet to the source address in a protocol that is not UDP, will the router forward that packet to ...
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1answer
3k views

Trouble acl-drop packets on a Cisco asa 5510

I am trying to troubleshoot the cause of "Flow is denied by configured rule (acl-drop)" packets on "show asp drop" on an ASA 8.4 I have done packet captures and packet traces, but I am not able to ...
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1answer
536 views

Problem with Cisco ASA 5512 NAT Configuration

I need help to resolve this issue. I have a Cisco ASA 5512 and I’m trying to access to my FTP server from external IP but the packets are dropped. Please find the network diagram below: I typed this ...
2
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1answer
989 views

PPPoE setup Cisco 881W

I've been trying to fix this myself but I'm afraid I can't. I've tried basically every tutorial already, but it still doesn't work. Can someone here write a tutorial on how to get PPPoE working with ...
1
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1answer
240 views

NAT issue with getting internet to end devices

So, in this (seemingly) never ending saga of me driving three hours to fail, I ran into another problem. I have a router and a switch on the side of a mountain that I need to get Internet to, and ...
5
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1answer
430 views

which host will reply to the ping?

suppose having a LAN which contains : FTP server (10.0.0.1) HTTP server (10.0.0.2) SSH server (10.0.0.3) the LAN use NAT overloading and it has a single public IP (1.2.3.4), now if I ping on 1.2.3.4 ...
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2answers
227 views

Lab] Cisco 881 external ip address pass through vs static nat

I am trying to get some clarification on how things should/can be done. I have 5 static ip's and need to get some servers direct access and some indirect access. I need to know is it possible to ...
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1answer
193 views

How to use dynamic NAT to allow access from customer RFC1918 subnets for access to Internet and LAN?

I am currently working on a project for a SP and one of their requests has me stumped. Background : The customer wants to move to a vendor's WAN solution and for the underlay , we are using DMVPN. ...
5
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4answers
37k views

Ping a private IP address in another network

We all know that PCs on a LAN use private IP addresses such as 192.168.2.3, etc. Now my question is, how can a PC say mine having a private address of 192.168.2.3 communicate with other LAN PC ...
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1answer
114 views

How to block outside initiated traffic in NPTv6?

NPTv6 does prefix translation between one IPv6 address to another. Is there a way to prevent outside initiated traffic to inside (preferably in A10 AX devices)?
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1answer
400 views

IPv4 to IPv6 one-to-one mapping for a whole Class A range

Are there any IPv6 technologies that support translating one-to-one mapping from IPv4 to IPv6 for the whole Class A range, like 10.0.0.0/8 network to a particular IPv6/40 range? Preferably for A10 AX ...
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2answers
1k views

Cisco performance issues C890 series

I'm working on a complex project that includes Linux and Cisco routers. I am fairly new to networking and i'm using cisco command lines for the first time, so please be nice and don't hesitate to ...
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1answer
770 views

VPN hairpin and port forwarding on ASA 5506x

I have a Cisco ASA5506x on which I want VPN hairpin so that all VPN traffic goes through the ASA A port forwarding for RDP (3389) to my RDP server I can get them to work separately depending on ...
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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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2answers
92 views

AWS private NAT

Here is the scenario I have two private subnets in two separate VPCs. On ranges: 10.0.0.0/16 10.1.0.0/16 The 10.1 subnet is connected to a VPN gateway to a customer's VPN that all works fine. The ...
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2answers
739 views

Hosting multiple web servers or web applications on a private network

If a web site is hosted on a public network it can directly be accessed using it IP. If it is hosted on a private network it can still be accesses if the NAT device conducts a port forwarding of some ...
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2answers
1k views

Port Forwarding Not Working on Mikrotik hap AC [closed]

I have set my MikroTik RouterBoard hap AC as the router instead of my Modem/Router that my ISP gave me. I'm trying to set port forwarding using a tutorial I've found in google. That's the ...
3
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1answer
19k views

Site-To-Site IPSec Tunnel behind NAT

Forgive me if this question is not for here. I have a situation where I need to connect Site-to-Site VPN between two offices but the company is small and a startup with a very tight budget. Thing is ...

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