Why do we need a NAT instance?












0














AWS beginner here. This question is about NAT instances.



As per the docs "You can use a network address translation (NAT) instance in a public subnet in your VPC to enable instances in the private subnet to initiate outbound IPv4 traffic to the Internet or other AWS services, but prevent the instances from receiving inbound traffic initiated by someone on the Internet."



But can this not be achieved by using a security group with outbound rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to receive only from within the VPC?



What am I missing here?






amazon-web-services amazon-ec2 aws-security-group aws-vpc







share|improve this question




















  • 1




    Sure it can. Its about fine grain security setup.
    – Antoniossss
    Sep 12 at 11:58










  • I can allow a co-worker to spin up the machines only in the private subnet and then I don't have to worry if they got the SG right.
    – Jakub Kania
    Sep 12 at 11:59










  • I recommend asking this question on security.stackexchange.com .
    – kenlukas
    Sep 12 at 12:17










  • See also Why do we need private subnets in VPC?
    – Michael - sqlbot
    Sep 12 at 17:33
















0














AWS beginner here. This question is about NAT instances.



As per the docs "You can use a network address translation (NAT) instance in a public subnet in your VPC to enable instances in the private subnet to initiate outbound IPv4 traffic to the Internet or other AWS services, but prevent the instances from receiving inbound traffic initiated by someone on the Internet."



But can this not be achieved by using a security group with outbound rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to receive only from within the VPC?



What am I missing here?






amazon-web-services amazon-ec2 aws-security-group aws-vpc







share|improve this question




















  • 1




    Sure it can. Its about fine grain security setup.
    – Antoniossss
    Sep 12 at 11:58










  • I can allow a co-worker to spin up the machines only in the private subnet and then I don't have to worry if they got the SG right.
    – Jakub Kania
    Sep 12 at 11:59










  • I recommend asking this question on security.stackexchange.com .
    – kenlukas
    Sep 12 at 12:17










  • See also Why do we need private subnets in VPC?
    – Michael - sqlbot
    Sep 12 at 17:33














0












0








0







AWS beginner here. This question is about NAT instances.



As per the docs "You can use a network address translation (NAT) instance in a public subnet in your VPC to enable instances in the private subnet to initiate outbound IPv4 traffic to the Internet or other AWS services, but prevent the instances from receiving inbound traffic initiated by someone on the Internet."



But can this not be achieved by using a security group with outbound rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to receive only from within the VPC?



What am I missing here?






amazon-web-services amazon-ec2 aws-security-group aws-vpc







share|improve this question















AWS beginner here. This question is about NAT instances.



As per the docs "You can use a network address translation (NAT) instance in a public subnet in your VPC to enable instances in the private subnet to initiate outbound IPv4 traffic to the Internet or other AWS services, but prevent the instances from receiving inbound traffic initiated by someone on the Internet."



But can this not be achieved by using a security group with outbound rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to receive only from within the VPC?



What am I missing here?






amazon-web-services amazon-ec2 aws-security-group aws-vpc




amazon-web-services amazon-ec2 aws-security-group aws-vpc






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Nov 12 at 19:25









slm

8,441105875




8,441105875










asked Sep 12 at 11:56









Aravind

11412




11412








  • 1




    Sure it can. Its about fine grain security setup.
    – Antoniossss
    Sep 12 at 11:58










  • I can allow a co-worker to spin up the machines only in the private subnet and then I don't have to worry if they got the SG right.
    – Jakub Kania
    Sep 12 at 11:59










  • I recommend asking this question on security.stackexchange.com .
    – kenlukas
    Sep 12 at 12:17










  • See also Why do we need private subnets in VPC?
    – Michael - sqlbot
    Sep 12 at 17:33














  • 1




    Sure it can. Its about fine grain security setup.
    – Antoniossss
    Sep 12 at 11:58










  • I can allow a co-worker to spin up the machines only in the private subnet and then I don't have to worry if they got the SG right.
    – Jakub Kania
    Sep 12 at 11:59










  • I recommend asking this question on security.stackexchange.com .
    – kenlukas
    Sep 12 at 12:17










  • See also Why do we need private subnets in VPC?
    – Michael - sqlbot
    Sep 12 at 17:33








1




1




Sure it can. Its about fine grain security setup.
– Antoniossss
Sep 12 at 11:58




Sure it can. Its about fine grain security setup.
– Antoniossss
Sep 12 at 11:58












I can allow a co-worker to spin up the machines only in the private subnet and then I don't have to worry if they got the SG right.
– Jakub Kania
Sep 12 at 11:59




I can allow a co-worker to spin up the machines only in the private subnet and then I don't have to worry if they got the SG right.
– Jakub Kania
Sep 12 at 11:59












I recommend asking this question on security.stackexchange.com .
– kenlukas
Sep 12 at 12:17




I recommend asking this question on security.stackexchange.com .
– kenlukas
Sep 12 at 12:17












See also Why do we need private subnets in VPC?
– Michael - sqlbot
Sep 12 at 17:33




See also Why do we need private subnets in VPC?
– Michael - sqlbot
Sep 12 at 17:33












1 Answer
1






active

oldest

votes


















3















But can this not be achieved by using a security group with outbound
rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to
receive only from within the VPC?




The above is true only if the instances also have a public IP address assigned to them. If they do not have a public IP assigned to them then the NAT gateway/instance is required for Internet access.






share|improve this answer





















  • Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
    – Aravind
    Sep 12 at 12:10










  • You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
    – Mark B
    Sep 12 at 12:26










  • @Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
    – John Hanley
    Sep 12 at 15:59













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3















But can this not be achieved by using a security group with outbound
rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to
receive only from within the VPC?




The above is true only if the instances also have a public IP address assigned to them. If they do not have a public IP assigned to them then the NAT gateway/instance is required for Internet access.






share|improve this answer





















  • Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
    – Aravind
    Sep 12 at 12:10










  • You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
    – Mark B
    Sep 12 at 12:26










  • @Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
    – John Hanley
    Sep 12 at 15:59


















3















But can this not be achieved by using a security group with outbound
rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to
receive only from within the VPC?




The above is true only if the instances also have a public IP address assigned to them. If they do not have a public IP assigned to them then the NAT gateway/instance is required for Internet access.






share|improve this answer





















  • Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
    – Aravind
    Sep 12 at 12:10










  • You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
    – Mark B
    Sep 12 at 12:26










  • @Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
    – John Hanley
    Sep 12 at 15:59
















3












3








3







But can this not be achieved by using a security group with outbound
rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to
receive only from within the VPC?




The above is true only if the instances also have a public IP address assigned to them. If they do not have a public IP assigned to them then the NAT gateway/instance is required for Internet access.






share|improve this answer













But can this not be achieved by using a security group with outbound
rule : "0.0.0.0/0: All traffic" and restricting the inbound rule to
receive only from within the VPC?




The above is true only if the instances also have a public IP address assigned to them. If they do not have a public IP assigned to them then the NAT gateway/instance is required for Internet access.







share|improve this answer












share|improve this answer



share|improve this answer










answered Sep 12 at 12:04









Mark B

99.4k15156172




99.4k15156172












  • Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
    – Aravind
    Sep 12 at 12:10










  • You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
    – Mark B
    Sep 12 at 12:26










  • @Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
    – John Hanley
    Sep 12 at 15:59




















  • Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
    – Aravind
    Sep 12 at 12:10










  • You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
    – Mark B
    Sep 12 at 12:26










  • @Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
    – John Hanley
    Sep 12 at 15:59


















Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
– Aravind
Sep 12 at 12:10




Thanks for the answer. If I do assign public IPs and restrict inbound traffic using a security group, am I in effect achieving the same thing as a NAT? I do understand that this may not be the right design, but just want to know if that is correct.
– Aravind
Sep 12 at 12:10












You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
– Mark B
Sep 12 at 12:26




You are achieving the goal to restrict traffic to outbound only. A NAT instance can provide additional things, for example logging of all outbound traffic, so the two methods aren't exactly "the same thing". Also, if you are using AWS Lambda functions that need to be in your VPC, then you can't assign public IPs to those, so a NAT is the only option to provide VPC Lambda functions with Internet access.
– Mark B
Sep 12 at 12:26












@Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
– John Hanley
Sep 12 at 15:59






@Aravind For devices inside a VPC to connect to devices outside the VPC, it needs one of the following: IGW (Internet Gateway), NAT Gateway, VGW, VPC EndPoint. Each type of device / connectivity option has its own features and benefits. Security Groups complement these connectivity options but do not replace them.
– John Hanley
Sep 12 at 15:59




















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