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Old July 14th, 2017, 03:22 AM   #1
yfcarer
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Question Trunk between 2 Stratix switch

Hi guys:

I have two Stratix switch, one 8300 layer 3 switch and another 8000 switch downstream.

I created VLAN 60,61 at 8000 switch by below command.
- EN
- Conf t
- Vlan 60
- Exit
- Conf t
- Vlan 61
- Exit

At the 8300 switch, I created VLAN through IExplorer and defined IP address, and subnet mask. Note there is already some other VLANs defined at this switch.

Then I choose one port at each switch, use below command to set it to trunk.
-EN
-Conf t
-Int F2/2 (for example)
-switchport mode trunk

When I have all my cable in place, I cannot ping to each other, and the syslog on the 8000 switch says "Native VLAN mismatch".

What is Native VLAN? Do I need to set it?
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Old July 14th, 2017, 05:13 AM   #2
robertkjonesjr
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In Cisco world, the native vlan on a trunk port is the untagged vlan; if you look at the traffic from a trunk port in a packet sniffer you would see that the traffic has a VLAN tag added to the header of the frame with the specific vlan that the frame belongs. This is how the next switch is informed as to what vlan this packet belongs.

So you will have this tag for all vlans except for one, and that is the native vlan. For Cisco, the default is vlan 1. So if you don't specify, packets belonging to vlan 1 will be untagged as they egress that port. All other packets from other vlans would be tagged appropriately with the VLAN header.

At the first switch where you created the two new vlans - are you sure you are using a trunk port?

You can verify the settings on each side with

show interfaces trunk

Example output:

Code:
2960G#show interfaces trunk

Port        Mode             Encapsulation  Status        Native vlan
Gi0/1       on               802.1q         trunking      1

Port        Vlans allowed on trunk
Gi0/1       1-4094
The native vlan will be called out. Check both sides of the link: what do they say?
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Old July 17th, 2017, 02:54 AM   #3
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Thank you Robertkjonesjr for your explaination.

I checked the setting on three different switches and get some screens in attached word document. SW01 is the layer 3 switch on top, SW06 is the new 8000 switch that doesn't work, SW04 is an existing 8000 switch which works with SW01.

The physical cable or fiber is connected as:
SW01 Gi1/2 – SW04 Gi1/1
SW01 Fa2/2 – SW06 Gi1/1

There is one difference on “Vlans in spanning tree forwarding state and not pruned”. The new switch shows none. Will this be the bad guy?

Quote:
Originally Posted by robertkjonesjr View Post
In Cisco world, the native vlan on a trunk port is the untagged vlan; if you look at the traffic from a trunk port in a packet sniffer you would see that the traffic has a VLAN tag added to the header of the frame with the specific vlan that the frame belongs. This is how the next switch is informed as to what vlan this packet belongs.

So you will have this tag for all vlans except for one, and that is the native vlan. For Cisco, the default is vlan 1. So if you don't specify, packets belonging to vlan 1 will be untagged as they egress that port. All other packets from other vlans would be tagged appropriately with the VLAN header.

At the first switch where you created the two new vlans - are you sure you are using a trunk port?

You can verify the settings on each side with

show interfaces trunk

Example output:

Code:
2960G#show interfaces trunk

Port        Mode             Encapsulation  Status        Native vlan
Gi0/1       on               802.1q         trunking      1

Port        Vlans allowed on trunk
Gi0/1       1-4094
The native vlan will be called out. Check both sides of the link: what do they say?
Attached Files
File Type: docx SW VLAN.docx (220.7 KB, 8 views)
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Old July 17th, 2017, 04:10 AM   #4
robertkjonesjr
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It could be a spanning tree issue. I found this cisco bug from google:

CSCtf07138

Sounds somewhat similar. Next steps would be to debug spanning tree and figure out why those vlans are pruned.

Under SW01 / show interface trunk, there is only one port listed:

Fa1/2

Are there any others? This is not the port to either of your switches under review here.
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Old July 17th, 2017, 07:54 PM   #5
yfcarer
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Dog

Oh, For SW01, there are 5 ports in trunk mode. So attached screen.
I am thinking to run "show run all" to get all configuration to a file. Is this the right command?
Attached Images
File Type: jpg Capture.jpg (44.2 KB, 61 views)
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Old July 17th, 2017, 09:29 PM   #6
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I do "show run all" and get the configuration, do a compare as below.
Will the PVST vs. MST be the problem?
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File Type: jpg span.jpg (112.8 KB, 52 views)
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Old July 18th, 2017, 06:27 AM   #7
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I thought MSTP was to be compatible with Cisco's per-vlan spanning tree but I never mix them so do not know what types of issues you might come across. Some googling shows issues such as yours - where some vlans are blocked. I guess I would make them all match and then go from there - if it starts working, then you know where you have to debug.
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Old July 19th, 2017, 07:26 PM   #8
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Thank you Robertkjonesjr. It works when I set the STP to PVST for SW06. Thank you for your help along the problem.
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