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Avatar of pbrowne1996

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Trunking fiber switches Cisco 3750X

i have 2 switches that are connected via fiber ports with trunking enabled.  One switch is working fine however when i power on the 2nd switch, the link lights on the fiber ports flash for about 2 minutes then it goes off, and then subsequently the other switch stops communicating to devices.  The configs are identical on both switches however the only difference i am seeing is that when you do a sh vlan command, ports 1/2 on the switch that i am adding are showing in vlan 1 even though its not configured for vlan 1.  The working switch doesnt show ports 1/2 in vlan 1 at all.  Dont know if this is the reason for the switches failing when both are connected.  Any help would be appreciated.
Avatar of eeRoot

BR3 does not have "shutdown" in the VLAN1 interface, so it would show VLAN 1 as up even if nothing is using it.  It looks like channel-group 1 is used on ports 1/1/1, 1/1/1, 2/1/1, and 2/1/2.  If these four ports connect to the same switch, that's okay.  but if it's two different etherchannel links to different switches, then one of the connections should have the channel-group number changed.  Also, try changing the channel-group mode from "on" to "desirable".  And add "switchport nonegotiate" to the interfaces as well.
Are these two switches stacked with each other or stacked separately? Make sure your VTP domain and password match. Your config looks good, I haven't seen anything that stands out as incorrect.
Avatar of pbrowne1996


vlan1 is shutdown, maybe when i copied the config it didnt show up.  Both set of switches have 2 switches stacked together so altogether there are 4 total.  BR2 has 2 and BR3 has 2 switches.  The VTP domain is the same with no password.
When you do a 'show log' what types of errors do you see. Initially I don't see anything wrong with your configs, it's a pretty basic setup. Very similar to mine. I did notice one switch is version 15 and the other is 12.2- this shouldn't matter since you're trunking (it only matters when stacking).
The 'show log' errors only show the ports going up then down, nothing else in there other than that on both switches.  Again, the only difference i see between both switches other than the versions are when you do a 'show vlan'.  Under vlan 1 - Default, ports 1/1/1, 1/1/2, 1/1/3, 1/1/4, 2/1/1, 2/1/2, 2/1/3, and 2/1/4 show there for BC3.  However when you do the same for BC2, vlan 1 - Default only shows 1/1/3, 1/1/4, 2/1/1, 2/1/2, 2/1/3 and 2/1/4.  BC2 is the working one that talks to the rest of our network just fine through the fiber ports 1/1/1 and 1/1/2.
Are ports 1/1/1, 1/1/1, 2/1/1, and 2/1/2 connecting to the same switch?
ports 1/1/1 and 1/1/2 are both active with fiber connections on both switches.
Try eliminating connections. I'd recommend you try trunking via a single port each. If successful create the port channel and add ports one at a time.
So are 2/1/1 and 2/1/2 unused or going to a different switch?
Currently 2/1/1 and 2/1/2 are unused but once we can get the connectivity going, it will be going to another set of switches.
Avatar of tpitch-ssemc
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Thanks tpitch-ssemc.  That makes sense, thanks for the info and here's your points.