Solved

sh ip route question

Posted on 2010-08-30
5
534 Views
Last Modified: 2012-05-10
What does this mean?

 172.18.0.0/16 is variably subnetted, 2 subnets, 2 masks

I have 5 routers, 2 in particular are connected together via ethernet cable.  IP on R1 is 172.18.0.1.  IP on R2 is 172.18.0.2.  They are both using 255.255.0.0 subnet.  

How is this 'variably subnetted', and how are there 2 subnets and 2 masks?  I could see the 'L' interface being seen as subnetted, but not the 'C' interface since it is the default mask of 255.255.0.0.

Here is my full sh ip route:
R     172.15.0.0/16 [120/2] via 172.18.0.1, 00:00:06, FastEthernet0/0
R     172.16.0.0/16 [120/2] via 172.18.0.1, 00:00:06, FastEthernet0/0
R     172.17.0.0/16 [120/2] via 172.18.0.1, 00:00:06, FastEthernet0/0
      172.18.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.18.0.0/16 is directly connected, FastEthernet0/0
L        172.18.0.2/32 is directly connected, FastEthernet0/0
0
Comment
Question by:B1izzard
[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 6

Accepted Solution

by:
wpharaon earned 250 total points
ID: 33564476
Hello,

Variably subnetted is due to the fact that one of them has the default mask of 255.255.0.0 (the /16)
and the second has 255.255.255.255 (the /32).
0
 

Author Comment

by:B1izzard
ID: 33564494
So variably subnetted is not the same as VLSM?  Any idea why they would consider a class B 255.255.0.0 subnetted?
0
 
LVL 17

Assisted Solution

by:Kvistofta
Kvistofta earned 250 total points
ID: 33564503
It IS subnettet because you have a small part of it with a /32-mask. If you remove that loopback it will not say that it is variable subnetted anymore.

/Kvistofta
0
 

Author Comment

by:B1izzard
ID: 33564531
I understand why the /32 would be considered subnetted, just not the /16.  I changed my subnet mask to /17 and now it looks like this:
      172.18.0.0/16 is variably subnetted, 2 subnets, 2 masks
C        172.18.0.0/17 is directly connected, FastEthernet0/1
L        172.18.0.1/32 is directly connected, FastEthernet0/1

Now this makes more sense, as there are now in my opinion 2 subnets, the /17 and /32.  But I guess if Cisco says 255.255.0.0 is a subnet, then it's a subnet.
0
 
LVL 6

Expert Comment

by:wpharaon
ID: 33564593
It simply identifies the /16 subnet, to be subnetted variably to a /17 (255.255.128.0) and to another /32 (255.255.255.255) networks.
0

Featured Post

Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

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

Problem Description:   Couple of months ago we upgraded the ADSL line at our branch office from Home to Business line. The purpose of transforming the service to have static public IP’s. We were in need for public IP’s to publish our web resour…
The Cisco RV042 router is a popular small network interfacing device that is often used as an internet gateway. Network administrators need to get at the management interface to make settings, change passwords, etc. This access is generally done usi…
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…
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…

730 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