Solved: Re: Cisco Packet tracer lab issue - Can't ping between devices

ZohaibAli4149 · ‎08-14-2023

Hello, I've created a lab in Cisco Packet tracer and I'm trying to ping between AZ-SW01 (Switch) and Router (AZ-RT01). I have configured the VLAN 1 with an IP address for both router and switch. I've also no shut the ports that the router and switch are connected to. But I can't ping between the router and the switch:

Here are the configs:

David Ruess · ‎08-14-2023

OK so what you have is a couple things going on. He also explains it in the video of why what works and what doesn't. It also explains why your other cable worked. You don't need 2 cables.

The first interface you have it connected to G0/0/1 (before you connected the second interface) is a routed port (L3) which needs an IP to be able to pass traffic and ping. When Jeremy configured the VLAN IP on the router the interfaces associated with it were L2. He even shows you cant configure the IP on the L2 interface that's why he uses the VLAN on the router.

If you notice the second cable you connected to the router is port G0/1/2 which is in fact a L2 port and part of VLAN 1 by default (also explained in the video).

So to recap the reason it works with the second link connected is because its a L2 port on the router and its passing the traffic to the VLAN interface you have created. It didn't work on the first port because it was a L3 port and needs the IP configured. As you have it you can remove your first connection to the router and keep the G0/1/2 connection and your lab will function as intended.

If you need further clarification please don't hesitate to ask.

-David

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David Ruess · ‎08-14-2023

Hello,

Can you try configuring Interface G0/0/1 on the router with the IP address 192.168.1.1/24 and remove the VLAN configuration on there as well.

You should not configure VLANs on routers as they are a L2 construct and stop at the L3 device such as a router. The VLAN on the router is internal and you want be able to get past the physical interface with no IP is configured.

You may also need to configure a default-gateway on the Switch if what I provide above does not work but try it without it first.

-David

ZohaibAli4149 · ‎08-14-2023

I am following an online course on CBTNuggets and the guy has a live lab. I am trying to mimic his real lab set up in Cisco Packet tracer. He has configured it exactly like how it's shown in the images yet he's able to ping? How?

David Ruess · ‎08-14-2023

Can you link the video or Skill?

ZohaibAli4149 · ‎08-14-2023

https://www.cbtnuggets.com/learn/it-training/playlist/nrn:playlist:certification:5de7f007bb58090014814e25/66?autostart=1

ZohaibAli4149 · ‎08-14-2023

Ok very interesting. I am able to ping both Router and Switch, but I had to connect two Straight Through cable between router and switch for them to be pingable? Why is that?

David Ruess · ‎08-14-2023

OK so what you have is a couple things going on. He also explains it in the video of why what works and what doesn't. It also explains why your other cable worked. You don't need 2 cables.

The first interface you have it connected to G0/0/1 (before you connected the second interface) is a routed port (L3) which needs an IP to be able to pass traffic and ping. When Jeremy configured the VLAN IP on the router the interfaces associated with it were L2. He even shows you cant configure the IP on the L2 interface that's why he uses the VLAN on the router.

If you notice the second cable you connected to the router is port G0/1/2 which is in fact a L2 port and part of VLAN 1 by default (also explained in the video).

So to recap the reason it works with the second link connected is because its a L2 port on the router and its passing the traffic to the VLAN interface you have created. It didn't work on the first port because it was a L3 port and needs the IP configured. As you have it you can remove your first connection to the router and keep the G0/1/2 connection and your lab will function as intended.

If you need further clarification please don't hesitate to ask.

-David

ZohaibAli4149 · ‎08-14-2023

AHA! YES OMG YESS!!! SWEET BLISS. Thank You for explaining!!!! This was eating at my brain! But then why does he have two cables coming out of the router and going in to the switch:

David Ruess · ‎08-14-2023

Im not so sure he does. According to the diagram in the video the 2 router connections are going to the 2 switches and the third connection on the switch is going to an access point. If you look closely it looks like F0/3 is connected to the AP in your picture.