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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Why are External NAT ports different when both NATs are restricted cone? [duplicate]

I'm in the progress of implementing my own Signaling server with UDP hole punching, everything have been smooth up until both hosts were behind Restricted Cone NAT, then the ports for P2P ...
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NAT not working; can ping web from c3745 router, but not from VM [closed]

Topology: https://i.imgur.com/a1azOy0.jpg R1#show run Building configuration... Current configuration : 1269 bytes ! version 12.4 service timestamps debug datetime msec service timestamps log ...
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Checkpoint Firewall using wrong Source IP when establishing a VPN

I have a checkpoint VSX environment running r81 and I have a DMZ firewall that has two external interfaces. One that goes to the Internet and one that goes to a 10.0.0.0/8 network that connects to ...
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How are there still enough public IP addresses? [duplicate]

If I understand correctly, a NAT is a translation from your private IP to a public IP because there are not enough public IPv4 addresses. This way multiple devices across one network with private IPs ...
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why ip adresses are divided into network portion and host portion when we already have NAT [duplicate]

I don't understand why ip adresses are divided into network portion and host portion? is the host portion really necessary when we already have NAT? for example, if ip addresses only have network ...
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Trying To connect Router4 to internet

In the picture, I have a part of my topology. The concept is that I am trying to configure OSPF in my network. Internet is a nat cloud module. The routers are all iosv routers. ISP 1 has the following ...
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Configure NAT in Vyos Router

I have the following diagram, and I want that R2 and each client connected with R2 have access to the internet. For that I configured NAT in R1 with the following commands: #set nat source rule 10 ...
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How NAT router use layer4 contents in layer3?

I followed from this question and @PeterGreen's Answer , and come to know that NAT router working in layer3, but using layer4 contents(layer4 port number,layer4 checksum). My question is when layer3 ...
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Source Port NAT with VPN [duplicate]

I understand that a router (like an home router) does source port NAT (as the public IP for a LAN is normally one). If I run a VPN Client (like Open VPN) on a computer in the LAN and if the VPN packet ...
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Does Port Forwarding limit ports available to NAPT?

I'm wondering if routers limit the possible ports available to NAPT when port forwarding is configured. For example, given one public IP address all but two ports assigned via port forwarding, would ...
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Switching Internet connection on Cisco ASA

I use Cisco ASA in branches of our organization. Each device has an IPsec tunnel that connects to the main office. To access the global network each device also has a NAT. Recently, a task arose to ...
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Error cluster with packets balacing through NAT

Im trying to make a web cluster (HTTP and FTP) with 3 linux machines where the packets are balanced through NAT and im using Bridge interfaces and HSRP, because im using 2 routers(using c3660 image) ...
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What is the use of SNAT (Static Network Address Translation)?

If SNAT is used to map internal private IP addresses directly to a non-changing public IP address, why not simply assign the public IP addresses directly to each host itself? What advantage dose SNAT ...
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Why or when do we need Layer 2 NAT? [closed]

What is the point of public addresses in Layer 2? Why or when do we need it? When is it healthy to use? Or is it even a common thing? Sorry I am kinda new at networking and I just googled it but ...
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How can I use scapy to make a port appear open-device behind NAT?

This has been asked in stack overflow like 7 years back. I don't see the correct answer there. Is there any way to do this? While this packet keeps on being transmitting, doesn't the other end see the ...
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NAT in ASA (5505) Firewall is not working for VLANs configured in Layer3 Switch?

Toplogy: Tool Used: Cisco Packet Tracer Scenario: NAT for hosts in any of the VLANs of Layer3-Switch not working. Ping requests reaches outside server, but NAT is not working so ISP Router can't ...
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How to configure NAT in Cisco ASA Firewall for all VLANs connected to layer 3 switch? [closed]

Topology: How to set up NAT in Cisco ASA Firewall (in Packet Tracer), when there are VLANs in the network? In the current approach, NAT is not working to reach the server (8.8.8.8) from any of the ...
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Static NAT and PAT simultaneously for single real host IP?

currently I have in production static NAT applied for one host (192.168.1.10) which is translated to NAT IP 172.16.1.5: ip nat inside source static 192.168.1.10 172.16.1.5 ip access-list standard 10 ...
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Cisco 2851 Static NAT Entry - Similar Static Entry Already Exists

Thank you in advance. I have a few 2851 Cisco ISR. This is my NAT Pool config; ip nat pool NAT-Pool 38.xxx.xxx.193 38.xxx.xxx.206 prefix-length 28 ip nat inside source list 1 pool NAT-Pool overload ...
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What's the procedure to limit a subnet on a Cisco router from seeing another subnet when both are using NAT?

I have a Cisco 891F router. The internet is hooked up to G8. The student network is Vlan 200, and the Office is Vlan 100. (I know the internet has an internal subnet (192.168.1.5), but that's because ...
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NAT not working in cisco packet tracer

Cisco Router Version: 16.7(3r) Cisco Packet Tracer:8.0 x64 Router(config)#interface dialer 1 Router(config-if)#ip nat? % Unrecognized command Router(config-if)#ip nat ? % Unrecognized command Router(...
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Linux: address the same IP range (different networks) via two interfaces masqueraded [closed]

Not sure whether it can be done: Due to a legacy setup there are two separate networks that both use the same class C subnet 192.168.0.0/24. I have a Linux box with two physical interfaces wherein ...
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Are NAT external:internal mapping types the same for UDP and TCP

Suppose I use a STUN server (UDP) to determine that a client's NAT randomly assigns external port values. Does this imply that the client's NAT will also assign random external port values when using ...
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How to perform an inbound and outbound NAT at the same time in Pfsense?

I have a rule on a stormshield performing NAT on both the source and the destination address. It is done very simply in one rule. Example : --Before translation-- --After ...
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Private IP address vs Local IP address

Say a router is connected to two devices. Now the router will give those two devices different private IP addresses. The router itself has a private IP address (which serves as the default gateway for ...
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Questions about NAT

So i just started learning about NAT and networking in general. As powerful as this technology may seem, it was specifically made for reducing the amount of IPV4 addresses used throughout the internet,...
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Cisco ASA nat from inside to outside, but network that is routed to inside interface

So is it possible to nat from inside to outside interface but not the inside ip subnet, rather the ip subnet that is routed to inside interface? #object network remote_ip_subnet #subnet 192.168.1.0 ...
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How does NAT modify the headers correctly?

How does the process of replacing the incoming message (say from stackexchange) to the router, and modifying the header with my PC IP happen? How does the router know which IP to insert there? Is ...
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CGNAT port allocation

I'm planning to implement CGNAT in service provider with a10 networks. So, the question is how many private IP addresses I can NAT through one public IP ? One public IP = 64511 ports = 400 ports per ...
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Multiple VLANs with PAT

I'd like to know if it's acceptable/possible to use PAT with multiple VLANs, by using the same translated IP address for all VLANs.
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Is this a good network configuration?

I am trying to configure ip sla for non directed link . I have configured static route to reach to non directed link 1 configured track 2 configured ip sla 3 configured access-list 4 configured NAT 5 ...
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Palo Alto Firewall: Why is double NAT needed?

The diagram shows my current network configuration. (Where X is 10). I have the firewall interface E1/2 at the left configured to 192.168.10.1/24. It is in a trusted security zone. A DHCP server is ...
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Configure port forwarding with interface command within VRF

We are working with VRFs and having a look into the NVI NAT configuration. Without VRFs, we can configure following: ip nat source static tcp 10.0.0.2 80 interface Dialer1 80 ip nat source static tcp ...
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NAT Unable to Translate on Packet Return

I am currently working with the network above. When ever I send a packet across from a network, on the return to the router it is unable to translate back and ends up dropping the packet. I am how ...
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Why Does Symmetric NAT imply a TURN Server? [duplicate]

I am using ICE/STUN in the context of WEBRTC. I understand why STUN does not work with symmetric NAT. The answer to that question is here: why STUN doesn't work with symmetric NAT? I am asking a ...
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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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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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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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2 answers
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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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PIM Packet and NAT

Is it possible to NAT PIM Join packet? Assume the receiver and the source are in two different networks (address regimes). Thus NAT is required. The upstream source and the groupe are included in the ...
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3 votes
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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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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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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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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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2 votes
1 answer
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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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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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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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Trace internal equipement from Internet while answering

I would like to know if it's possible to achieve a traceroute of nodes on an internal network from an equipement on the internet answering to a query. Let's say that a client on an internal network ...
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Is NAT66 a Viable Option to Protect Client?

Due to the addressing scheme of IPv6, each client now is able to get and directly use Globally-Routable Address (GUA) from the ISP. But that poses bigger security threat because attacker can directly ...
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1 vote
3 answers
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Combining NAT an tunneling

I was reading a text and a doubt came to mind. Suppose there is an interface in a router that implements NAT. That same interface is the extreme of a tunnel. If I was to send a message through said ...
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