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Do all network devices need to make routing decisions, regardless of communication across networks or within a network?

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1

From Hunt's TCP/IP Network Adminstration:

Gateways route data between networks, but all network devices, hosts as well as
gateways, must make routing decisions.

Is it correct that routing decisions are made only for communication across different networks?

For communication within a network (whether it is in an internetwork or not),

• does any device in the network need to make routing decisions?




• does any device in the network necessarily have a routing table or something similar?

If a device makes routing decision, that that mean the device has a routing table or something similar? If a device has a routing table or something similar, does it make routing decision?

Or, do only gateway devices have to make routing decisions and have routing tables or something similar?

I have these questions because my Linux laptop isn't a gateway in the local wifi network, but has a routing table to my surprise. Is it cecause any device in a network has a routing table? My laptop doesn't seem to connect two networks, because the network for all the loopback addresses and the wifi network can't communicate with each other. But its routing table shows a route for communicating with other devices in the same wifi network, and a default route for all other destinations outside the wifi network.

Thanks.

routing

share|improve this question

edited 10 hours ago

Tim

asked 10 hours ago

TimTim

624517

add a comment | 

1

From Hunt's TCP/IP Network Adminstration:

Gateways route data between networks, but all network devices, hosts as well as
gateways, must make routing decisions.

Is it correct that routing decisions are made only for communication across different networks?

For communication within a network (whether it is in an internetwork or not),

• does any device in the network need to make routing decisions?




• does any device in the network necessarily have a routing table or something similar?

If a device makes routing decision, that that mean the device has a routing table or something similar? If a device has a routing table or something similar, does it make routing decision?

Or, do only gateway devices have to make routing decisions and have routing tables or something similar?

I have these questions because my Linux laptop isn't a gateway in the local wifi network, but has a routing table to my surprise. Is it cecause any device in a network has a routing table? My laptop doesn't seem to connect two networks, because the network for all the loopback addresses and the wifi network can't communicate with each other. But its routing table shows a route for communicating with other devices in the same wifi network, and a default route for all other destinations outside the wifi network.

Thanks.

routing

share|improve this question

edited 10 hours ago

Tim

asked 10 hours ago

TimTim

624517

add a comment | 

From Hunt's TCP/IP Network Adminstration:

Gateways route data between networks, but all network devices, hosts as well as
gateways, must make routing decisions.

Is it correct that routing decisions are made only for communication across different networks?

For communication within a network (whether it is in an internetwork or not),

• does any device in the network need to make routing decisions?




• does any device in the network necessarily have a routing table or something similar?

If a device makes routing decision, that that mean the device has a routing table or something similar? If a device has a routing table or something similar, does it make routing decision?

Or, do only gateway devices have to make routing decisions and have routing tables or something similar?

I have these questions because my Linux laptop isn't a gateway in the local wifi network, but has a routing table to my surprise. Is it cecause any device in a network has a routing table? My laptop doesn't seem to connect two networks, because the network for all the loopback addresses and the wifi network can't communicate with each other. But its routing table shows a route for communicating with other devices in the same wifi network, and a default route for all other destinations outside the wifi network.

Thanks.

routing

share|improve this question

edited 10 hours ago

Tim

asked 10 hours ago

TimTim

624517

share|improve this question

edited 10 hours ago

Tim

asked 10 hours ago

TimTim

624517

share|improve this question

edited 10 hours ago

Tim

asked 10 hours ago

TimTim

624517

asked 10 hours ago

TimTim

624517

asked 10 hours ago

TimTim

624517

2 Answers
2

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6

Every IP device has a routing table, and therefore makes a routing decision. It may be quite simple with only two entries, but fundamentally, a device needs to decide if the destination is on the directly connected network or not. If not, it forwards the packet to the gateway. For most devices like PCs, there is only a default gateway, but there can be more than one.

share|improve this answer

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

add a comment | 

4

Theoretically, consider a computer that has an IP address of 192.168.1.3/24 and wants to send some data to the IP address 192.168.2.5/24 then it should make a subnet checking to see if the IP address it wants to reach is in the same network or not; to be able to decide to forward the packet to its gateway or not.

when you have a subnet mask of /24 which refers in binary to 11111111.11111111.11111111.00000000. Zeros are the places you can modify your IP address in the "same network". If you change anything before zeros start, it means you are changing the network you are in and to be able to communicate with such an IP you need a router between two of them. After all, being able to make this decision is considered as making a routing decision.

Hope the answer helps.

share|improve this answer

answered 10 hours ago

metinmetin

664

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metin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

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6

Every IP device has a routing table, and therefore makes a routing decision. It may be quite simple with only two entries, but fundamentally, a device needs to decide if the destination is on the directly connected network or not. If not, it forwards the packet to the gateway. For most devices like PCs, there is only a default gateway, but there can be more than one.

share|improve this answer

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

add a comment | 

6

Every IP device has a routing table, and therefore makes a routing decision. It may be quite simple with only two entries, but fundamentally, a device needs to decide if the destination is on the directly connected network or not. If not, it forwards the packet to the gateway. For most devices like PCs, there is only a default gateway, but there can be more than one.

share|improve this answer

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

add a comment | 

Every IP device has a routing table, and therefore makes a routing decision. It may be quite simple with only two entries, but fundamentally, a device needs to decide if the destination is on the directly connected network or not. If not, it forwards the packet to the gateway. For most devices like PCs, there is only a default gateway, but there can be more than one.

share|improve this answer

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

share|improve this answer

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

answered 10 hours ago

Ron TrunkRon Trunk

39.1k33780

4

Theoretically, consider a computer that has an IP address of 192.168.1.3/24 and wants to send some data to the IP address 192.168.2.5/24 then it should make a subnet checking to see if the IP address it wants to reach is in the same network or not; to be able to decide to forward the packet to its gateway or not.

when you have a subnet mask of /24 which refers in binary to 11111111.11111111.11111111.00000000. Zeros are the places you can modify your IP address in the "same network". If you change anything before zeros start, it means you are changing the network you are in and to be able to communicate with such an IP you need a router between two of them. After all, being able to make this decision is considered as making a routing decision.

Hope the answer helps.

share|improve this answer

answered 10 hours ago

metinmetin

664

New contributor

metin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

4

Theoretically, consider a computer that has an IP address of 192.168.1.3/24 and wants to send some data to the IP address 192.168.2.5/24 then it should make a subnet checking to see if the IP address it wants to reach is in the same network or not; to be able to decide to forward the packet to its gateway or not.

when you have a subnet mask of /24 which refers in binary to 11111111.11111111.11111111.00000000. Zeros are the places you can modify your IP address in the "same network". If you change anything before zeros start, it means you are changing the network you are in and to be able to communicate with such an IP you need a router between two of them. After all, being able to make this decision is considered as making a routing decision.

Hope the answer helps.

share|improve this answer

answered 10 hours ago

metinmetin

664

New contributor

metin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

Theoretically, consider a computer that has an IP address of 192.168.1.3/24 and wants to send some data to the IP address 192.168.2.5/24 then it should make a subnet checking to see if the IP address it wants to reach is in the same network or not; to be able to decide to forward the packet to its gateway or not.

when you have a subnet mask of /24 which refers in binary to 11111111.11111111.11111111.00000000. Zeros are the places you can modify your IP address in the "same network". If you change anything before zeros start, it means you are changing the network you are in and to be able to communicate with such an IP you need a router between two of them. After all, being able to make this decision is considered as making a routing decision.

Hope the answer helps.

share|improve this answer

answered 10 hours ago

metinmetin

664

New contributor

metin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this answer

answered 10 hours ago

metinmetin

664

New contributor

metin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered 10 hours ago

metinmetin

664

New contributor

metin is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered 10 hours ago

metinmetin

664