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Multiple VLAN trunking from 3750 or 2960G to an SLM2024

erics
Level 1
Level 1

Hello,

We have a pair of new SLM2024s we want to add into our topology. Our current core switch is a stacked 3750. We have a 2960G attached to that. Most things work, but we can't trunk multiple VLANs between the 2024s and the other units. I've tried on both the 2960G and the 3750.

On the 2024, there isn't much to configure. It just knows when a port needs to be in trunking mode. Just to be sure, I've set the connecting port to accept tagged traffic on the other VLANs I want it to accept, but no configuration I've set on the connecting ports for VLAN seems to make any difference.

When I tried on the 2960G, I only set the port with "switchport mode trunk", and "sh int trunk" shows its trunking all the VLANs.

When I tried on the 3750, I used the same as above, but added "switchport trunk encapsulation dot1q"

If I leave it like that, I can move traffic on and off the 2024 on VLAN 1 only. If I add a "switchport trunk native XX", then I can move traffic on that VLAN only. Assuming that the 2960G and 3750 are tagging all VLAN traffic not in native, then it seems that the 2024 is dropping all incoming tagged traffic, but accepting untagged traffic from the native VLAN of the connected switch.

The 2024s are communicating with each other on the various VLANs just fine.

Just so it's said, I'm not plugging the 2024 into the 2960G and the 3750 at the same time, nor am I plugging more than one 2024 directly into the rest of the network at any given time, although the pair have been connected to each other most of the time. I have tried breaking the link so that I've only got one 2024 in the mix, but that hasn't made any positive or negative differences at all.

4 Replies 4

Jon Marshall
Hall of Fame
Hall of Fame

Eric

Under the "Port to Vlan" configuration option on the SLM2024 can you make sure that the vlans you want to pass on the trunk link are -

1) not excluded

2) are configured to be tagged (except the PVID obviously)

I think from your description you have already done this but can you make sure that the PVID matches the native vlan on your 2950 or 3750 switch.

Jon

Thanks for the suggestions, Jon.

The VLANs I'm currently trying to get to the 2024 are 10 and 100. So, I've set the connecting port to 1U/10T/100T. However, I can change anything I want on that, even excluding the VLANs, and it doesn't make any difference at all.

All PVID's on the 2024 are 1. I didn't see anything in the configs about changing the native VLAN for the 3750 or 2960G except on some ports and port-channels, so I assume that means they're still native in 1 (I'm not a Cisco guy, I inherited the 3750 and 2960G from a previous administration of whom no one is left).

VTP is all transparent everywhere else in the organization, and if the SLM2024 has an accessible CLI, I don't know how get to it.

raviragmail
Level 1
Level 1

Hi Eric

just try the following

Set a port on your core (3750  )  as trunk by following commands

goto switch interface e.g

interface fa 1/0/48

    Switchport mode trunk

    Switchport encapsulation trunk dot1q

goto priviledge mode

execute following show command

sh vtp status brief

note down the VTP domain name..e.g  VTP name is Eric

now come to SLM 2024

set a trunk port by following commands

interface gi 0/24

    Switchport mode trunk

    Switchport encapsulation trunk dot1q

goto global configuration mode

   

execute following command

vtp mode client

vtp domain Eric ... which we have taken on 3750 by sh VTP status brief command

now...

sh vlan

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

so if you configure the above accurately, you will see all your vlans on 3750 will available on SLM2024.

Raghvendra

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