Is "Bcast" default gateway?

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Is "Bcast" default gateway?

Postby hack3rcon » 2019-01-27 07:45

Hello.
Is "Bcast" default gateway?

Thank you.
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Re: Is "Bcast" default gateway?

Postby p.H » 2019-01-27 09:23

No, it is the broadcast address.
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Re: Is "Bcast" default gateway?

Postby hack3rcon » 2019-01-27 11:44

p.H wrote:No, it is the broadcast address.

Is you mean "255.255.255.255" ? I guess in a VLAN network it can be something else.
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Re: Is "Bcast" default gateway?

Postby Head_on_a_Stick » 2019-01-27 11:50

hack3rcon wrote:
p.H wrote:No, it is the broadcast address.

Is you mean "255.255.255.255" ?

No, that is the netmask.

The broadcast address can be found with
Code: Select all
ip a

Check for brd in the output.
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Re: Is "Bcast" default gateway?

Postby hack3rcon » 2019-01-27 11:57

Head_on_a_Stick wrote:
hack3rcon wrote:
p.H wrote:No, it is the broadcast address.

Is you mean "255.255.255.255" ?

No, that is the netmask.

The broadcast address can be found with
Code: Select all
ip a

Check for brd in the output.

In the internet network "255.255.255.255" is not broadcast address?
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Re: Is "Bcast" default gateway?

Postby Head_on_a_Stick » 2019-01-27 12:09

Head_on_a_Stick wrote:The broadcast address can be found with
Code: Select all
ip a

Check for brd in the output.

Correction: check the inet line for the succeeding brd statement in the stanza for the given interface.

For example:
Code: Select all
empty@shinken:~ $ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp0s25: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
    link/ether 8a:3b:33:e5:04:d3 brd ff:ff:ff:ff:ff:ff
3: wlp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether b6:02:aa:1c:0f:a8 brd ff:ff:ff:ff:ff:ff
 ** inet 192.168.1.77/24 brd 192.168.1.255 scope global dynamic wlp2s0 **
       valid_lft 70461sec preferred_lft 70461sec
    inet6 fe80::b402:aaff:fe1c:fa8/64 scope link
       valid_lft forever preferred_lft forever
empty@shinken:~ $

^ The asterisks show the line in question, in my case the broadcast address is 192.168.1.255
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Re: Is "Bcast" default gateway?

Postby p.H » 2019-01-27 12:33

Head_on_a_Stick wrote:
hack3rcon wrote:
p.H wrote:No, it is the broadcast address.

Is you mean "255.255.255.255" ?

No, that is the netmask.

There can be actually two broadcast addresses.

One is the so-called "directed" broadcast address, defined as the last (or rarely first) address in the IP subnet, received by all hosts within the IP subnet.. It is routable when the subnet is routable. This is the one configured and displayed with ifconfig or ip addr.

Another one is the so-called "limited" broadcast address, defined as 255.255.255.255, received by all hosts connected to the broadcast domain (ethernet network or VLAN). It is not routable.
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