<p>When you are buying servers you can order multiple IP per one server, typically in the same /8 or /16 subnet. So 1 server can serve as 100 or even 1000 Bitcoin nodes. </p>

<p>Ordering lots of IPs in lots of different /16 subnets is rarely possible for the same server. </p>

<p>Hence this change makes it harder/more expensive to launch 1000's of rogue Bitcoin nodes - you will have to distribute them across large number of servers in different datacenters.</p>

CC BY-SA 3.0
2017-11-24T07:15:03.397Z
2017-11-24T07:15:03.397Z
BarsMonster
<p>In <a href="https://en.bitcoin.it/wiki/Weaknesses#Sybil_attack" rel="nofollow noreferrer">Bitcoin Wiki Weaknesses: Sybil attack</a> they mention that:</p>

<p>"Bitcoin makes these attacks more difficult by only making an outbound connection to one IP address per /16 (x.y.0.0)".</p>

<p>Why would this make a Sybil attack more difficult? Is there a reason for choosing a /16 subnet or is it randomly chosen by the developers with no background?
Wouldn't it be more secure to choose a smaller subnet?</p>

<network><connection><sybil-attack>
Sybil attack countermeasure
user1
# Sybil attack countermeasure

(Asked by: username_0 on 2017-11-23)

In [Bitcoin Wiki Weaknesses: Sybil attack](https://en.bitcoin.it/wiki/Weaknesses#Sybil_attack) they mention that:

"Bitcoin makes these attacks more difficult by only making an outbound connection to one IP address per /16 (x.y.0.0)".

Why would this make a Sybil attack more difficult? Is there a reason for choosing a /16 subnet or is it randomly chosen by the developers with no background?
Wouldn't it be more secure to choose a smaller subnet?

**Tags:** network, connection, sybil-attack


---

## 1 answers

### Answer by username_1 on 2017-11-24. Score: 3

When you are buying servers you can order multiple IP per one server, typically in the same /8 or /16 subnet. So 1 server can serve as 100 or even 1000 Bitcoin nodes.

Ordering lots of IPs in lots of different /16 subnets is rarely possible for the same server.

Hence this change makes it harder/more expensive to launch 1000's of rogue Bitcoin nodes - you will have to distribute them across large number of servers in different datacenters.


---

