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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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Site-to-Site VPN with BOTH sites behind NAT (mobile data routers)

I have 2 sites (call them "A" and "B") which connect to the Internet using 4G mobile data routers - don't knock them, I'm getting 200Mbps downlink and 30Mbps uplink, faster than a ...
kbro's user avatar
  • 121
2 votes
1 answer
113 views

Do NAT Gateways Need to be the First Address of the Network?

NAT gateways are often given the first usable address in an address space. Do any protocol specs require this? Or is this just a convention? I skimmed RFC 1918 and RFC 2663 but didn't see anything ...
Brett Holman's user avatar
0 votes
2 answers
209 views

How does NATing work

I'm not 100% understanding how NATing works. Let me setup our network and talk this through. So first of all, lets say that I have an IP size of 4 bits so 16 possible combination. The only private ...
Jenia Be Nice Please's user avatar
1 vote
0 answers
273 views

Full Cone NAT on Cisco router in Packet Tracer

I am trying to create a network with two subnetworks with private IPs. I need to configure symmetric NAT on edge routers within the subnetwork. Diagram: I need to configure NAT on Router0 and Router2....
Filip's user avatar
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0 votes
1 answer
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Is it possible to send network messages with "Fake" Local Network(192.168.x.x) destination IP but actually reaches the destination via internet?

I am configuring a MySQL server that is only intended for computers from internal network/local network machines to access. Now MySQL has a "bind IP address" setting that, if I set it to the ...
cr001's user avatar
  • 103
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1 answer
787 views

Cisco ASA VPN tunnel shows up (phase 1 and 2, MM_ACTIVE), but no traffic passes

My end of the tunnel is on an ASAv in AWS. (version 9.14) show crypto isakmp sa 4 IKE Peer: 212.239.x.y Type : L2L Role : responder Rekey : no State : ...
Chris Holt's user avatar
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0 answers
15 views

How are we still able to use IPv4 address even with NAT? [duplicate]

My question is why haven't we run out of IPv4 public IP as well because now almost all home has a router which is assigned a public IP. Is it possible to have multiple layers of NAT on the router-ISP ...
Himanshuman's user avatar
0 votes
1 answer
126 views

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 ...
Blip's user avatar
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1 vote
1 answer
1k views

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
0 votes
3 answers
293 views

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
1 answer
80 views

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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3 votes
2 answers
4k views

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 ...
user avatar
0 votes
3 answers
439 views

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 ...
S. M.'s user avatar
  • 398
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2 answers
70 views

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
  • 3
0 votes
1 answer
114 views

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 ...
Ruslan's user avatar
  • 155
1 vote
2 answers
1k views

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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1 answer
1k views

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
1 vote
2 answers
211 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 ...
Vishwa Mithra Tatta's user avatar
1 vote
1 answer
470 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 ...
Rajan's user avatar
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1 answer
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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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0 votes
1 answer
210 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 ...
Somedude007's user avatar
1 vote
1 answer
119 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 ...
TBone's user avatar
  • 113
2 votes
1 answer
513 views

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(...
AlpGUL's user avatar
  • 23
1 vote
1 answer
98 views

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
0 votes
1 answer
62 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 ...
Thomas Braun's user avatar
1 vote
1 answer
1k 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 ...
molik's user avatar
  • 13
2 votes
3 answers
1k 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 ...
nicks101's user avatar
  • 123
4 votes
3 answers
416 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,...
Ninja's user avatar
  • 143
1 vote
1 answer
380 views

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 ...
John's user avatar
  • 812
1 vote
1 answer
851 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 ...
Minsky's user avatar
  • 115
0 votes
1 answer
529 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 ...
zeronight's user avatar
0 votes
1 answer
121 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.
Yasmine's user avatar
0 votes
1 answer
83 views

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
0 votes
2 answers
2k 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 ...
HotPotTofu's user avatar
0 votes
0 answers
338 views

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 ...
Mario Jost's user avatar
  • 1,729
0 votes
2 answers
88 views

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
0 votes
0 answers
32 views

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
0 votes
1 answer
327 views

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
  • 101
1 vote
2 answers
1k views

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
0 votes
2 answers
128 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
0 votes
2 answers
347 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
  • 103
0 votes
3 answers
308 views

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
  • 107
3 votes
1 answer
278 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 ...
Chris Holt's user avatar
0 votes
1 answer
528 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
  • 31
1 vote
0 answers
60 views

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
0 votes
1 answer
321 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
  • 3
2 votes
1 answer
292 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
118 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
114 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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