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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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 ...
The Footsie's user avatar
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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 ...
sydevloper's user avatar
2 votes
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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 ...
ECHO's user avatar
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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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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 ...
Q31's user avatar
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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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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 ...
Keylime Pi's user avatar
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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 ...
Red And Black's user avatar
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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 ...
Vishwa Mithra Tatta's user avatar
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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 ...
Rajan's user avatar
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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 ...
Somedude007's user avatar
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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 ...
Marcus Ilgner's user avatar
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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 ...
Thomas Braun's user avatar
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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 ...
nicks101's user avatar
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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,...
Ninja's user avatar
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1 answer
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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 ...
Minsky's user avatar
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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 ...
zeronight's user avatar
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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.
Yasmine's user avatar
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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 ...
wajib rehman's user avatar
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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 ...
HotPotTofu's user avatar
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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 ...
Christian's user avatar
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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 ...
GroovyDotCom's user avatar
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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 ...
nycynik's user avatar
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2 answers
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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 ...
Strategist's user avatar
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2 answers
117 views

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 ...
Verudux's user avatar
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2 answers
299 views

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 ...
Bastien's user avatar
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3 answers
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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 ...
huseyin39's user avatar
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3 votes
1 answer
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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 ...
Chris Holt's user avatar
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1 answer
492 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 ...
Rohit's user avatar
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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 ...
user1977050's user avatar
5 votes
2 answers
2k views

Can a client-side outbound TCP port be reused concurrently for multiple destinations?

Can a client-side outbound TCP port be reused concurrently for multiple destinations? If it's possible, this would let NAT gateways milk an IP Address much more, and make it practically impossible to ...
Kind Contributor's user avatar
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1 answer
296 views

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 ...
perelt's user avatar
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2 votes
1 answer
289 views

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/...
Christopher Allen's user avatar
1 vote
1 answer
116 views

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 ...
Script Kiddies's user avatar
1 vote
1 answer
113 views

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 ...
James's user avatar
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1 vote
3 answers
102 views

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 ...
S. Brottes's user avatar
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2 answers
129 views

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 ...
maximillian1's user avatar
1 vote
3 answers
350 views

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 ...
shaymin shaymin's user avatar
1 vote
1 answer
95 views

How to Mitigate DoS by Bindings/Transport Address Exhaustion in NAT64?

Let's say a NAT64 Router only has 1 IPv4 address for bindings, meaning the NAT64 router has a roughly 65535 IPv4 transport addresses. A malicious attacker can then exhaust the entire IPv4 transport ...
maximillian1's user avatar
0 votes
2 answers
328 views

Why cant't IPSec's Transport Mode ESP be used in NAT64 although ESP doesn't sign the new IP header?

In RFC6146 stated: Any protocols that protect IP header are incompatible with NAT64. This implies that end-to-end IPsec verification will fail when the Authentication Header (AH) is used (both ...
maximillian1's user avatar
1 vote
1 answer
398 views

Why does CLAT in 464XLAT architecture use Stateless NAT64 instead of Stateful?

As of my understanding, stateless NAT is using 1:1 translation, meaning it needs one IPv4 address for one IPv6 address vice versa, thus not preserving IPv4. Since the CLAT is supposed to be router/...
maximillian1's user avatar
2 votes
2 answers
3k views

General: What is a dynamic gateway, how does it work, where is it used?

I saw this option in my OPNsense gateway configuration, and was hoping someone could shed light on what it is, exactly: Dynamic gateway policy: [YES/NO] This interface does not require an ...
Avery Freeman's user avatar

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