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 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 do I port forward between 2 private subnets? [closed]

I am trying to implement a dual firewall DMZ on my homelab similar to this website: https://danielmiessler.com/study/dmz/ Initially in the DMZ there will only be a reverse proxy and a web server on ...
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doubts ethernet NIC [closed]

I have a question, it may be stupid but I have that doubt I have an ethernet card for fiber optics, if my ethernet card is 1 gb / s I think that is the bandwidth of the interface and my fiber optic is ...
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2answers
39 views

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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1answer
29 views

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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1answer
47 views

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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36 views

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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1answer
32 views

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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1answer
38 views

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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1answer
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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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1answer
30 views

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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1answer
130 views

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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3answers
771 views

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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3answers
350 views

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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1answer
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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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1answer
31 views

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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1answer
41 views

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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1answer
32 views

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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1answer
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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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2answers
349 views

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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2answers
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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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1answer
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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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2answers
46 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 ...
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2answers
74 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 ...
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52 views

PIM Packet and NAT

Is it possible to NAT PIM Join packet? Assume the receiver and the source are in two different private network. Thus NAT is required. The upstream source and the groupe are included in the PIM Join ...
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1answer
135 views

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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1answer
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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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0answers
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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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How does 2 computers both behind NAT routers handle communication? [duplicate]

Currently reading up on TCP/IP protocol stack, while I was reading about the Network Interface layers, I started reading about NAT, and how it meant to decrease the amount of IPv4 used, by using the ...
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1answer
76 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 ...
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1answer
246 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/...
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1answer
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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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1answer
52 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 ...
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3answers
100 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 ...
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2answers
72 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 ...
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3answers
95 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 ...
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1answer
55 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 ...
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2answers
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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 ...
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1answer
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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/...
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2answers
654 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 ...
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1answer
176 views

Is an IPSec connection between 2 devices behind NAT possible?

We have tens of IPSec connections between our office and customer site's. We use an extra router in the customer network (so behind NAT) to initiate the connection to our office where a PFSense router ...
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1answer
43 views

How to connect to a machine which is sitting behind NAT router?

I have a server that needs to push a message to a client from which it received a request a few days ago. Now request which was received has the IP address of the NAT router behind which the client ...
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2answers
221 views

Cisco Port forward ip nat inside source static ... Invalid

This is almost the same question as How to setup port forwarding on Cisco Router running Version 15.2(4)M6. The problem is that the command used in the answer is not available: ip nat inside source ...
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1answer
56 views

Why does my enterprise issue me a public IP address instead of just a private IP address?

Let's say I work for a big enterprise organization. When looking at my IP address, I notice that it is not a private IP address but is instead a public IP address. What are the benefits of ...
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2answers
66 views

NATTing a server address

I need help writing NAT rule for this use case: I want to be able to connect to an local IP as though it's the remote server IP. e.g. port forwarding. I don't have access to the firewall on the remote ...
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1answer
316 views

Cisco NAT - Overload PAT and Static nat from one inside to two outside interfaces

i have following setup Cisco ISR4k Router with one inside LAN interface and two outside Interfaces. ---- WAN1 (NAT outside) LAN (NAT inside) -- ISR4k | ...

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