Still celebrating National IT Professionals Day with 3 months of free Premium Membership. Use Code ITDAY17

x
?
Solved

IP address summary

Posted on 2015-01-12
5
Medium Priority
?
153 Views
Last Modified: 2015-01-21
I am trying to figure out why the 2 prefixes below would summarize 192.168.1.0/24, .2.0/24, and .3.0/24:

192.168.0.0/21 and 192.168.0.0/22
0
Comment
Question by:leblanc
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
5 Comments
 
LVL 83

Accepted Solution

by:
David Johnson, CD, MVP earned 668 total points
ID: 40546024
192.168.0.0/21 doesn't 192.168.0.1-192.168.7.254 broadcast 192.168.7.255
192.168.0.0/22 does      192.168.0.1-192.168.3.254 broadcast 192.168.3.255
You need to understand how CIDR works
a prefix size of /22 gives: 2^32-22 = 2**10 addresses 1024
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 1332 total points
ID: 40546472
The best you could accomplish is

192.168.1.0/24
192.168.2.0/23 (which includes 2.0 & 3.0)

There is no way to summarize all three networks with a single prefix (without including networks that shouldn't be included).
0
 
LVL 1

Author Comment

by:leblanc
ID: 40560871
"192.168.0.0/21 doesn't 192.168.0.1-192.168.7.254 broadcast 192.168.7.255". I am not sure I understand this. It looks like /21 cover .1.0, .2.0, and .3.0/24
0
 
LVL 50

Assisted Solution

by:Don Johnston
Don Johnston earned 1332 total points
ID: 40560950
The reason why 192.168.0.0/21 won't work is because you are over summarizing.  That prefix includes networks:

192.168.0.0/24
192.168.1.0/24
192.168.2.0/24
192.168.3.0/24
192.168.4.0/24
192.168.5.0/24
192.168.6.0/24
192.168.7.0/24

So while the prefix does include 1.0, 2.0 and 3.0, it also includes a bunch of networks that you don't want advertised.
0
 
LVL 1

Author Comment

by:leblanc
ID: 40560999
ah... Got it.
0

Featured Post

Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In this article, I am going to show you how to simulate a multi-site Lab environment on a single Hyper-V host. I use this method successfully in my own lab to simulate three fully routed global AD Sites on a Windows 10 Hyper-V host.
This article is in regards to the Cisco QSFP-4SFP10G-CU1M cables, which are designed to uplink/downlink 40GB ports to 10GB SFP ports. I recently experienced this and found very little configuration documentation on how these are supposed to be confi…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
Monitoring a network: how to monitor network services and why? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the philosophy behind service monitoring and why a handshake validation is critical in network monitoring. Software utilized …

670 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question