Native VLAN Mismatch while doing intervlan routing

nor · ‎05-20-2022

I am trying to configure a banking enterprise network. Just started. So, I put a switch in each department. A specific vlan for each. I have configured the layer 3 switch ports with vlan 10 and vlan 20. and given them ip addresses as well. And I am able to ping from vlan 10 to 20. However, I get native vlan mismatch error on both the switches and I cant seem to figure out how to fix it. Am I trying to do this wrong, or am I just missing a simple command?

Let me know if i should provide more information..

Flavio Miranda · ‎05-20-2022

Hi

You are probably missing some command. Did you configure "native vlan " on trunk between switches? If you did, did you use the same vlan ID ?

You can also attach your PacketTracer project here. Just zip it first.

nor · ‎05-20-2022

I configured the ports on layer 3 switch as access ports. With vlans. Attached file

Flavio Miranda · ‎05-20-2022

Hi

find attached a working file. You did some mistakes:

- Interface between switches must be in trunk mode. You configured as access,

-Vlan need to be created on the access switch

-You need to enable routing on the L3 switch "ip routing"

-The interfaces where the PC is connected must be place in the correct vlan.

Take a close look on my file and let me know if you have any question.

nor · ‎05-20-2022

I understood. Ive been trying to replicate those configurations myself. But the pcs dont ping. Can you let me know what Im doing wrong

Flavio Miranda · ‎05-20-2022

Hi @nor

All good this time except you forgot to create vlan 10 and 20 on the L3 switch. If you run the command "show ip int br"

you are going to see this:

Vlan1 unassigned YES unset administratively down down

Vlan10 192.168.10.1 YES manual down down

Vlan20 192.168.20.1 YES manual down down

You need to create the vlans.

After you create the vlan with command:

vlan 10

vlan 20

You are going to see this:

Vlan1 unassigned YES unset administratively down down

Vlan10 192.168.10.1 YES manual up up

Vlan20 192.168.20.1 YES manual up up

Then, you can ping.

Try it by yourself and let me know.

nor · ‎05-20-2022

Oooo. I forgot to actually create the vlan riiight. I see. That was super helpful. Thank you. If I have more questions regarding this assignment but its not on the same topic (intervlan routing), should i make another post or can i reply here?

Flavio Miranda · ‎05-20-2022

You can ask here for sure. what´s in your mind?

nor · ‎05-20-2022

Next step is to implement redundancy. I did the same configurations on the second layer 3 switch, and trunked the ports connecting them both. It pings, but when I go into simulation mode and send a packet, it shows the packet making unnecessary travels. So STP isnt taking place then?

Flavio Miranda · ‎05-20-2022

Yes, it is:

Switch#sh spanning-tree

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 0000.0C04.9158

Cost 19

Port 23(FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address 0060.3E53.5157

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 20

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/1 Altn BLK 19 128.1 P2p

Fa0/2 Altn BLK 19 128.2 P2p

Fa0/23 Root FWD 19 128.23 P2p

You can see that the ports on Multilayer Switch0 that connects to both Access switches are in "BLK", which means Block state.

However, the way you did is not correct. You cannot have two devices with the same IP configuration on the network because it will cause conflict.

If you want to do redundancy on this network, you need to learn about VRRP/HSRP protocol. This is the correct way to do redundancy on this case.

nor · ‎05-20-2022

Ah. I see. I figured out how to do HSRP with routers. But I cant seem to find any scenario to learn from thats similar to mine. (redundancy with layer 3 switch)

Flavio Miranda · ‎05-20-2022

Take a look on the file attached.

You can see that vlan 20 on both switch L3 have differents IP address. But, you can see that the HRSP have IP address of 192.168.20.1. This IP is the VIP of the HRSP and the gateway of the PC.

Now, if you shud down one L3 switch, the other L3 switch will responde this IP 192.168.20.1 and you have Layer 3 redundancy.

nor · ‎05-20-2022

Understood. Is there any reason you didn't do it on vlan 10 as well? What should I do now to make it so that the pcs can communicate, since they cant ping each other anymore.

Flavio Miranda · ‎05-20-2022

Check it out.

Now both vlan has VRRP and both PC ping each other.

If you run "show standby" you are going to see that one L3 switch is the Active and the other is the standby

Switch 1:

Switch#sh standby

Vlan10 - Group 0

State is Standby

3 state changes, last state change 08:27:52

Virtual IP address is 192.168.10.1

Active virtual MAC address is 0000.0C07.AC00

Local virtual MAC address is 0000.0C07.AC00 (v1 default)

Hello time 3 sec, hold time 10 sec

Next hello sent in 1.836 secs

Preemption disabled

Active router is 192.168.10.3

Standby router is local

Priority 100 (default 100)

Group name is hsrp-Vl1-0 (default)

Vlan20 - Group 0

State is Standby

7 state changes, last state change 01:33:03

Virtual IP address is 192.168.20.1

Active virtual MAC address is 0000.0C07.AC00

Local virtual MAC address is 0000.0C07.AC00 (v1 default)

Hello time 3 sec, hold time 10 sec

Next hello sent in 1.148 secs

Preemption disabled

Active router is 192.168.20.3, priority 150 (expires in 9 sec)

MAC address is 0000.0C07.AC00

Standby router is local

Priority 100 (default 100)

Group name is hsrp-Vl2-0 (default)

Switch 0:

Switch#sh standby

Vlan10 - Group 0

State is Active

7 state changes, last state change 08:27:24

Virtual IP address is 192.168.10.1

Active virtual MAC address is 0000.0C07.AC00

Local virtual MAC address is 0000.0C07.AC00 (v1 default)

Hello time 3 sec, hold time 10 sec

Next hello sent in 2.719 secs

Preemption disabled

Active router is local

Standby router is 192.168.10.2

Priority 100 (default 100)

Group name is hsrp-Vl1-0 (default)

Vlan20 - Group 0

State is Active

4 state changes, last state change 01:32:53

Virtual IP address is 192.168.20.1

Active virtual MAC address is 0000.0C07.AC00

Local virtual MAC address is 0000.0C07.AC00 (v1 default)

Hello time 3 sec, hold time 10 sec

Next hello sent in 2.264 secs

Preemption disabled

Active router is local

Standby router is 192.168.20.2, priority 100 (expires in 6 sec)

Priority 150 (default 100)

Group name is hsrp-Vl2-0 (default)

nor · ‎05-24-2022

Sorry about the late reply. Been busy working on the assignment. If you don't mind. Will you be able to take a look one last time at the HSRP configuration of the the two routers on the very left. They dont seem to communicate and both stays active.