does :::80 in netstat output means only ipv6 or ipv6+ipv4?

If I am listening on :::80, is it listening on all ipv6 or all ipv6+ipv4?

This is my netstat -tln:

tcp        0      0 :::8080                     :::*

edited Jan 23 at 10:36

asked Jan 23 at 6:40

Akhil J

447

4

Possible duplicate of meaning of Netstat local address column

– Olorin
Jan 23 at 6:43

3

@Olorin None of the answers in the question you linked to address the specific question asked (whether the socket listens on only ipv6 or both ipv6 and ipv4).

– Johan Myréen
Jan 23 at 7:50

1

@JohanMyréen "The above options show up as:- :::80 ... and translate to:- ... Listen on any IP address (IPv4 or IPv6)"

– Olorin
Jan 23 at 8:13

3

@Olorin As I wrote in my answer, the situation is not that clear-cut.

– Johan Myréen
Jan 23 at 8:18

1

@JohanMyréen in that case that answer should be edited, no?

– Olorin
Jan 23 at 8:20

|
show 1 more comment

If I am listening on :::80, is it listening on all ipv6 or all ipv6+ipv4?

This is my netstat -tln:

tcp        0      0 :::8080                     :::*

edited Jan 23 at 10:36

asked Jan 23 at 6:40

Akhil J

447

4

Possible duplicate of meaning of Netstat local address column

– Olorin
Jan 23 at 6:43

3

@Olorin None of the answers in the question you linked to address the specific question asked (whether the socket listens on only ipv6 or both ipv6 and ipv4).

– Johan Myréen
Jan 23 at 7:50

1

@JohanMyréen "The above options show up as:- :::80 ... and translate to:- ... Listen on any IP address (IPv4 or IPv6)"

– Olorin
Jan 23 at 8:13

3

@Olorin As I wrote in my answer, the situation is not that clear-cut.

– Johan Myréen
Jan 23 at 8:18

1

@JohanMyréen in that case that answer should be edited, no?

– Olorin
Jan 23 at 8:20

|
show 1 more comment

If I am listening on :::80, is it listening on all ipv6 or all ipv6+ipv4?

This is my netstat -tln:

tcp        0      0 :::8080                     :::*

edited Jan 23 at 10:36

asked Jan 23 at 6:40

Akhil J

447

If I am listening on :::80, is it listening on all ipv6 or all ipv6+ipv4?

This is my netstat -tln:

tcp        0      0 :::8080                     :::*

networking ipv6 ipv4

edited Jan 23 at 10:36

asked Jan 23 at 6:40

Akhil J

447

edited Jan 23 at 10:36

asked Jan 23 at 6:40

Akhil J

447

edited Jan 23 at 10:36

asked Jan 23 at 6:40

Akhil J

447

asked Jan 23 at 6:40

Akhil J

447

asked Jan 23 at 6:40

Akhil J

447

4

Possible duplicate of meaning of Netstat local address column

– Olorin
Jan 23 at 6:43

3

@Olorin None of the answers in the question you linked to address the specific question asked (whether the socket listens on only ipv6 or both ipv6 and ipv4).

– Johan Myréen
Jan 23 at 7:50

1

@JohanMyréen "The above options show up as:- :::80 ... and translate to:- ... Listen on any IP address (IPv4 or IPv6)"

– Olorin
Jan 23 at 8:13

3

@Olorin As I wrote in my answer, the situation is not that clear-cut.

– Johan Myréen
Jan 23 at 8:18

1

@JohanMyréen in that case that answer should be edited, no?

– Olorin
Jan 23 at 8:20

|
show 1 more comment

4

Possible duplicate of meaning of Netstat local address column

– Olorin
Jan 23 at 6:43

3

@Olorin None of the answers in the question you linked to address the specific question asked (whether the socket listens on only ipv6 or both ipv6 and ipv4).

– Johan Myréen
Jan 23 at 7:50

1

@JohanMyréen "The above options show up as:- :::80 ... and translate to:- ... Listen on any IP address (IPv4 or IPv6)"

– Olorin
Jan 23 at 8:13

3

@Olorin As I wrote in my answer, the situation is not that clear-cut.

– Johan Myréen
Jan 23 at 8:18

1

@JohanMyréen in that case that answer should be edited, no?

– Olorin
Jan 23 at 8:20

Possible duplicate of meaning of Netstat local address column

– Olorin
Jan 23 at 6:43

@Olorin None of the answers in the question you linked to address the specific question asked (whether the socket listens on only ipv6 or both ipv6 and ipv4).

– Johan Myréen
Jan 23 at 7:50

@JohanMyréen "The above options show up as:- :::80 ... and translate to:- ... Listen on any IP address (IPv4 or IPv6)"

– Olorin
Jan 23 at 8:13

@Olorin As I wrote in my answer, the situation is not that clear-cut.

– Johan Myréen
Jan 23 at 8:18

@JohanMyréen in that case that answer should be edited, no?

– Olorin
Jan 23 at 8:20

|
show 1 more comment

1 Answer
1

active

oldest

votes

A listening socket that is bound to ::, i.e. any address IPv6 address (INADDR6_ANY), may or may not also listen to connections using IPv4. This depends from several things:

Some operating systems are what is known as dual stack, and on those operating systems this depends from whether the IPV6_V6ONLY socket option is set on the listening socket (by the program that created the socket). Linux-based operating systems and FreeBSD are examples of such operating systems.
The default behavior if the option is not explicitly set by a program is OS dependent. On Linux-based operating systems, for example, you can change this default by writing 0 or 1 to /proc/sys/net/ipv6/bindv6only.

Some other operating systems are not dual stack, and on those operating systems one cannot ever listen to both IPv6 and IPv4 with a single socket. OpenBSD is one such operating system.

On some operating systems, the output of netstat will tell you whether the socket is dual-stack. FreeBSD's netstat reports dual-stack sockets as tcp46 and udp46 in the first column of the output, for examples.

Thanks for your answer @Johan Myreen I want to improve this answer
with examples.

I am testing the ipv6_only behavior with both values.

cat /proc/sys/net/ipv6/bindv6only

0

nc -6 -l 80

#server started

# netstat

tcp6       0      0 :::80                   :::*                    LISTEN     

# nc client

nc localhost 80

test

# server response 

nc -6 -l 80

test

# from ipv6 now

 nc ::1 80

test ipv6

# server response

nc -6 -l 80

test ipv6

cat /proc/sys/net/ipv6/bindv6only

1

# server started

nc -6 -l 80

# connect to ipv4

nc localhost 80

nc: connect to localhost port 80 (tcp) failed: Connection refused

# connect to ipv6 

nc ::1 80 

test ipv6 

# server respose

nc -6 -l 80

test ipv6

from above results we can see that value of /proc/sys/net/ipv6/bindv6only deciding the behaviour of ipv6 only or ipv6+ipv4

edited Jan 23 at 10:36

Akhil J

447

answered Jan 23 at 7:47

Johan Myréen

7,64411524

1

The term dual stack is usually used in a context where you just care about having both IPv4 and IPv6 support and do not care about implementations details such as whether you use one or two sockets to achieve that result. As such what you describe for OpenBSD could still be called dual stack.

– rfc2460
Jan 25 at 13:08

add a comment |

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1 Answer
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1 Answer
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A listening socket that is bound to ::, i.e. any address IPv6 address (INADDR6_ANY), may or may not also listen to connections using IPv4. This depends from several things:

Some operating systems are what is known as dual stack, and on those operating systems this depends from whether the IPV6_V6ONLY socket option is set on the listening socket (by the program that created the socket). Linux-based operating systems and FreeBSD are examples of such operating systems.
The default behavior if the option is not explicitly set by a program is OS dependent. On Linux-based operating systems, for example, you can change this default by writing 0 or 1 to /proc/sys/net/ipv6/bindv6only.

Some other operating systems are not dual stack, and on those operating systems one cannot ever listen to both IPv6 and IPv4 with a single socket. OpenBSD is one such operating system.

Thanks for your answer @Johan Myreen I want to improve this answer
with examples.

I am testing the ipv6_only behavior with both values.

cat /proc/sys/net/ipv6/bindv6only

0

nc -6 -l 80

#server started

# netstat

tcp6       0      0 :::80                   :::*                    LISTEN     

# nc client

nc localhost 80

test

# server response 

nc -6 -l 80

test

# from ipv6 now

 nc ::1 80

test ipv6

# server response

nc -6 -l 80

test ipv6

cat /proc/sys/net/ipv6/bindv6only

1

# server started

nc -6 -l 80

# connect to ipv4

nc localhost 80

nc: connect to localhost port 80 (tcp) failed: Connection refused

# connect to ipv6 

nc ::1 80 

test ipv6 

# server respose

nc -6 -l 80

test ipv6

from above results we can see that value of /proc/sys/net/ipv6/bindv6only deciding the behaviour of ipv6 only or ipv6+ipv4

edited Jan 23 at 10:36

Akhil J

447

answered Jan 23 at 7:47

Johan Myréen

7,64411524

1

The term dual stack is usually used in a context where you just care about having both IPv4 and IPv6 support and do not care about implementations details such as whether you use one or two sockets to achieve that result. As such what you describe for OpenBSD could still be called dual stack.

– rfc2460
Jan 25 at 13:08

add a comment |

A listening socket that is bound to ::, i.e. any address IPv6 address (INADDR6_ANY), may or may not also listen to connections using IPv4. This depends from several things:

Some operating systems are what is known as dual stack, and on those operating systems this depends from whether the IPV6_V6ONLY socket option is set on the listening socket (by the program that created the socket). Linux-based operating systems and FreeBSD are examples of such operating systems.
The default behavior if the option is not explicitly set by a program is OS dependent. On Linux-based operating systems, for example, you can change this default by writing 0 or 1 to /proc/sys/net/ipv6/bindv6only.

Some other operating systems are not dual stack, and on those operating systems one cannot ever listen to both IPv6 and IPv4 with a single socket. OpenBSD is one such operating system.

Thanks for your answer @Johan Myreen I want to improve this answer
with examples.

I am testing the ipv6_only behavior with both values.

cat /proc/sys/net/ipv6/bindv6only

0

nc -6 -l 80

#server started

# netstat

tcp6       0      0 :::80                   :::*                    LISTEN     

# nc client

nc localhost 80

test

# server response 

nc -6 -l 80

test

# from ipv6 now

 nc ::1 80

test ipv6

# server response

nc -6 -l 80

test ipv6

cat /proc/sys/net/ipv6/bindv6only

1

# server started

nc -6 -l 80

# connect to ipv4

nc localhost 80

nc: connect to localhost port 80 (tcp) failed: Connection refused

# connect to ipv6 

nc ::1 80 

test ipv6 

# server respose

nc -6 -l 80

test ipv6

from above results we can see that value of /proc/sys/net/ipv6/bindv6only deciding the behaviour of ipv6 only or ipv6+ipv4

edited Jan 23 at 10:36

Akhil J

447

answered Jan 23 at 7:47

Johan Myréen

7,64411524

1

The term dual stack is usually used in a context where you just care about having both IPv4 and IPv6 support and do not care about implementations details such as whether you use one or two sockets to achieve that result. As such what you describe for OpenBSD could still be called dual stack.

– rfc2460
Jan 25 at 13:08

add a comment |

A listening socket that is bound to ::, i.e. any address IPv6 address (INADDR6_ANY), may or may not also listen to connections using IPv4. This depends from several things:

Some operating systems are what is known as dual stack, and on those operating systems this depends from whether the IPV6_V6ONLY socket option is set on the listening socket (by the program that created the socket). Linux-based operating systems and FreeBSD are examples of such operating systems.
The default behavior if the option is not explicitly set by a program is OS dependent. On Linux-based operating systems, for example, you can change this default by writing 0 or 1 to /proc/sys/net/ipv6/bindv6only.

Some other operating systems are not dual stack, and on those operating systems one cannot ever listen to both IPv6 and IPv4 with a single socket. OpenBSD is one such operating system.

Thanks for your answer @Johan Myreen I want to improve this answer
with examples.

I am testing the ipv6_only behavior with both values.

cat /proc/sys/net/ipv6/bindv6only

0

nc -6 -l 80

#server started

# netstat

tcp6       0      0 :::80                   :::*                    LISTEN     

# nc client

nc localhost 80

test

# server response 

nc -6 -l 80

test

# from ipv6 now

 nc ::1 80

test ipv6

# server response

nc -6 -l 80

test ipv6

cat /proc/sys/net/ipv6/bindv6only

1

# server started

nc -6 -l 80

# connect to ipv4

nc localhost 80

nc: connect to localhost port 80 (tcp) failed: Connection refused

# connect to ipv6 

nc ::1 80 

test ipv6 

# server respose

nc -6 -l 80

test ipv6

from above results we can see that value of /proc/sys/net/ipv6/bindv6only deciding the behaviour of ipv6 only or ipv6+ipv4

edited Jan 23 at 10:36

Akhil J

447

answered Jan 23 at 7:47

Johan Myréen

7,64411524

A listening socket that is bound to ::, i.e. any address IPv6 address (INADDR6_ANY), may or may not also listen to connections using IPv4. This depends from several things:

Some operating systems are what is known as dual stack, and on those operating systems this depends from whether the IPV6_V6ONLY socket option is set on the listening socket (by the program that created the socket). Linux-based operating systems and FreeBSD are examples of such operating systems.
The default behavior if the option is not explicitly set by a program is OS dependent. On Linux-based operating systems, for example, you can change this default by writing 0 or 1 to /proc/sys/net/ipv6/bindv6only.

Some other operating systems are not dual stack, and on those operating systems one cannot ever listen to both IPv6 and IPv4 with a single socket. OpenBSD is one such operating system.

Thanks for your answer @Johan Myreen I want to improve this answer
with examples.

I am testing the ipv6_only behavior with both values.

cat /proc/sys/net/ipv6/bindv6only

0

nc -6 -l 80

#server started

# netstat

tcp6       0      0 :::80                   :::*                    LISTEN     

# nc client

nc localhost 80

test

# server response 

nc -6 -l 80

test

# from ipv6 now

 nc ::1 80

test ipv6

# server response

nc -6 -l 80

test ipv6

cat /proc/sys/net/ipv6/bindv6only

1

# server started

nc -6 -l 80

# connect to ipv4

nc localhost 80

nc: connect to localhost port 80 (tcp) failed: Connection refused

# connect to ipv6 

nc ::1 80 

test ipv6 

# server respose

nc -6 -l 80

test ipv6

from above results we can see that value of /proc/sys/net/ipv6/bindv6only deciding the behaviour of ipv6 only or ipv6+ipv4

edited Jan 23 at 10:36

Akhil J

447

answered Jan 23 at 7:47

Johan Myréen

7,64411524

edited Jan 23 at 10:36

Akhil J

447

edited Jan 23 at 10:36

Akhil J

447

edited Jan 23 at 10:36

Akhil J

447

answered Jan 23 at 7:47

Johan Myréen

7,64411524

answered Jan 23 at 7:47

Johan Myréen

7,64411524

answered Jan 23 at 7:47

Johan Myréen

7,64411524

1

The term dual stack is usually used in a context where you just care about having both IPv4 and IPv6 support and do not care about implementations details such as whether you use one or two sockets to achieve that result. As such what you describe for OpenBSD could still be called dual stack.

– rfc2460
Jan 25 at 13:08

add a comment |

1

The term dual stack is usually used in a context where you just care about having both IPv4 and IPv6 support and do not care about implementations details such as whether you use one or two sockets to achieve that result. As such what you describe for OpenBSD could still be called dual stack.

– rfc2460
Jan 25 at 13:08

The term dual stack is usually used in a context where you just care about having both IPv4 and IPv6 support and do not care about implementations details such as whether you use one or two sockets to achieve that result. As such what you describe for OpenBSD could still be called dual stack.

– rfc2460
Jan 25 at 13:08

add a comment |

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