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Using /31 masks on point-to-point links

Latest reply: Sep 14, 2021 16:01:52 862 59 38 0 2

Using /31 masks on point-to-point links


Hello everyone! 

Today, I would like to present a practical example of how to configure point-to-point links using /31 according to RFC3021.


Objetive


The purpose of this post is to present an addressing configuration using 31-bit prefixes on point-to-point links as specified in RFC3021.

Understanding RFC3021 and the use of 31-bit prefixes.


RFC 3021 describes the use of 31-bit prefixes on point-to-point links. This reserves only one bit for the host portion. Thus, the value 0 represents the host at one end and the value 1 represents the other host of the connection.


01


Using 31-Bit Prefixes on IPv4 Point-to-Point Links


RFC 3021 describes using 31-bit prefixes for point-to-point links. This leaves 1 bit for the host-id portion of the IP address. Normally a host-id of all zeros is used to represent the network or subnet, and a host-id of all ones is used to represent a directed broadcast. Using 31-Bit prefixes, the host-id of 0 represents one host, and a host-id of 1 represents the other host of a point-to-point link.


Local link (limited) broadcasts (255.255.255.255) can still be used with 31-bit prefixes. But directed broadcasts are not possible to a 31-bit prefix. This is not really a problem because most routing protocols use multicast, limited broadcasts, or unicasts.


The following is an example configuration on a point-to-point link:

02

03

04


Connectivity test between the two interfaces configured with /31:


05

06


Conclusion:

If it was possible to perform the addressing configuration using /31 and the connectivity test using ping was successful, our example is complete.


Reference:

  • https://www.ietf.org/rfc/rfc3021.txt

  • https://datatracker.ietf.org/doc/html/rfc3021




The post is synchronized to: Author group

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little_fish
Admin Created Jul 22, 2021 14:54:47

good
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andersoncf1
andersoncf1 Created Jul 22, 2021 16:54:55 (0) (0)
thanks mate  
carlosalcosta
Created Jul 22, 2021 16:04:20

Excellent. Thanks for sharing.
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andersoncf1
andersoncf1 Created Jul 22, 2021 16:55:12 (0) (0)
welcome bro  
Faridrami
Created Jul 22, 2021 16:10:37

Thanks for sharing
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azkasaqib
azkasaqib Created Jul 22, 2021 16:53:01 (1) (0)
 
azkasaqib
azkasaqib Created Jul 22, 2021 16:53:06 (0) (0)
 
andersoncf1
andersoncf1 Created Jul 22, 2021 17:14:54 (1) (0)
welcome  
Faridrami
Faridrami Reply azkasaqib  Created Jul 26, 2021 16:18:41 (0) (0)
 
Faridrami
Faridrami Reply andersoncf1  Created Jul 26, 2021 16:19:01 (0) (0)
 
Assis_bsb
Assis_bsb Created Sep 14, 2021 16:02:09 (1) (0)
 
Faridrami
Faridrami Reply Assis_bsb  Created Sep 14, 2021 16:20:09 (0) (0)
 
Vlada85
MVE Author Created Jul 22, 2021 16:16:36

Thank you for sharing
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andersoncf1
andersoncf1 Created Jul 22, 2021 17:14:39 (0) (0)
welcome mate  
azkasaqib
Created Jul 22, 2021 16:52:43

Thank you for sharing
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andersoncf1
andersoncf1 Created Jul 22, 2021 17:14:20 (0) (0)
welcome  
azkasaqib
Created Jul 22, 2021 16:52:49

Using /31 masks on point-to-point links-4046443-1
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andersoncf1
andersoncf1 Created Jul 22, 2021 17:14:28 (0) (0)
 
lucian2003
MVE Author Created Jul 23, 2021 01:19:54

Thanks so much
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andersoncf1
andersoncf1 Created Jul 23, 2021 17:31:14 (0) (0)
welcome  
Andre_G
Created Jul 23, 2021 02:48:31

excellent, this can save more reserved ip when we are using ptp Using /31 masks on point-to-point links-4047073-1
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andersoncf1
andersoncf1 Created Jul 23, 2021 17:30:57 (0) (0)
of corse kkk  
Unicef
MVE Created Jul 23, 2021 05:17:15

Very good and useful
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Saqib123
Saqib123 Created Jul 24, 2021 16:12:17 (0) (0)
 
Saqib123
Saqib123 Created Jul 24, 2021 16:12:25 (0) (0)
 
andersoncf1
andersoncf1 Created Jul 24, 2021 17:13:13 (0) (0)
thanks  

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