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CDP-4-NATIVE_VLAN_MISMATCH

Hi, our network chap has come in and configured our switches and has since left. When logged into the switches to dump the config from the two 3560 switches in the server room I was getting the following error on the console for both switches.

CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/47 (1), with switch-mdf GigabitEthernet!

Now, Port 47 on the client switch is running: switchport trunk encapsulation isl

Whereas port 47 on the core switch (hostname is switch-mdf) is running: switchport access vlan 3 switchport mode access

There is an uplink cable between the two ports 47 to link both switches. Now I'm no cisco expert but should we disable the trunking on the client switch and set all ports to default blank, ie in the config set the port

interface GigabitEthernet0/47 !

My understanding is this would make a standard non-trunked port, and as we are plugging the switch into the core switches port 47, all ports on the client switch would then be part of vlan 3 (which is what i would like).

Could someone please kindly confirm if my thinking is correct, and commands to fix the above would be appreciated if anyone has the time. Im trying to get hold of the network guy in the meantime but to no avail. Although there is this mismatch the switch seems to have detected it and ignored it.

Thanks in advance,

Chris

Reply to
g18c
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So you've got an ISL trunk on 0/47 on switch A

And 0/47 on switch B (or whatever is on the recieving end of the above mentioned interface) is configured as an access port that calls VLAN 3 home.

Is that correct so far? If so, what you have is not a trunk just yet.

Depends on whether or not you need the wire between these two ports 47 to carry multiple VLANS across to the other switch. If you need these (you do not have one interface in each of these vlans attached to a routed interface, for example... if so, then you need a trunk and the thing to do is configure the access port as a trunk, specifically an isl trunk.

The native vlan mismach error is likely because the trunk wants to call VLAN 1 home. I cannot recall at the moment if that is so whether the trunk is up or not.... but it is the default behavior of trunks... and bad behavior at that. In any case, you need these ports configured as access ports, or as trunk ports.

Your thinking is correct. I would add only this caution... as always, the network will do what you tell it to do, but it will not always do what you expect it to do. If you reconfigured 0/47 on switch A to be an access port residing in VLAN 3, then you have those two ports in harmony and vlan 3 will presumably live on both sides of the link.

The switch doesn't really care what the trunk (which, when properly configured is a member of all ports) calls its "native" vlan. But you should care. IMHO, all trunks should come out of vlan 1 and into their own vlan. But that is a horse of another color.

Hope this helps.

Reply to
st.john.gogarty

My apologies.... I misspoke when I said: "the trunk (which, when properly configured is a member of all ports)'"

What I meant to say, rather, is that a trunk is member of all vlans.

Reply to
st.john.gogarty

Thanks for the prompt reply.

i just need switch B to be a member for hosts pcs, all ports will be on the same vlan. i think i need to do some reading!

Thanks,

Chris

Reply to
g18c

If you do not need to carry different VLANS on the port (as you mentioned, all ports will be in the same VLAN), you should remove all trunking configuration from both switches on that port, and configure the port with the same VLAN. Just configure the port 47 as an access port with your "hosts PCs VLAN", and configure all ports (including your uplink) with the same VLAN in your "switch B".

Good luck,

Mike

Reply to
headsetadapter.com

Ok thanks for the reply. Thats what i want. Ok so question is i moved from port 47 to a normal access port on VLAN 3 from switch A, and connected to a port on switch B. i think by default all ports are VLAN1 from factory settings.

Now since no vlan information is passed over a standard access port how is the switch complaining? is it the CDP protocol and a warning poping up? ill reconfigure all ports as suggested.

Thanks,

Chris

Reply to
g18c

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