gns3 with layer 3 switch

Posted on 2016-10-30
Last Modified: 2016-11-01
I use the NM-16ESW with my 3725 IOS to simulate the layer 3 switch on my GNS3 version 1.3.13. I configured the SVI and a defaiult route. When I did show IP route, my last resort route was not set. Any ideas experts?. Thanks
Question by:leblanc
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Expert Comment

by:Niten Kumar
ID: 41866417
Have you run the command ip default-gateway X.X.X.X command to setup the switch default gateway where X.X.X.X is router IP.

By the way there is a better way to simulate a L3 switch in GNS3 where you can get actual switch simulation.  I believe in your case you are using a router and adding a module to simulate a switch.
LVL 29

Accepted Solution

Predrag Jovic earned 300 total points
ID: 41866422
Does next hop exist and is reachable (interfaces up up)?
If not - default route will be removed.
If yes - most likely GNS3 bug.

If routing is enabled default gateway is not used.

With GNS3 sometimes is enough to turn off and on lab (or to recreate it again) and everything works.
Also check recommended IOS image versions for your GNS3. To have recommended IOS version can save you a lot of troubles (the same as the least buggy version of GNS3).

Author Comment

ID: 41866954
ip routing command is enabled. So I use the ip route and the strange thing is I could not ping the next hop even though everything is up & up. Itis just two layer 3 switches connected to each other.

What is the  better way to simulate a L3 switch in GNS3?
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Assisted Solution

by:Niten Kumar
Niten Kumar earned 200 total points
ID: 41867741
You will need a good Windows machine with at least 8GB ram and above.  Check the guide at the following link:

If you are stuck anywhere or find any part confusing then let me know.  Glad to help.

Author Comment

ID: 41867762
There was something going on with GNS3 STP. I restarted Windows and GNS3 and now it is working.

Awesome. I will try that. Thanks
LVL 29

Expert Comment

by:Predrag Jovic
ID: 41868440
You can try UNL, a little bit complicated to make it work, but one of my colleagues prepared  most of CCIE on it. Not sure how good it is, I just started to have fun with it (day1). There are tutorials on youtube how to configure it.

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