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Problems with Trunk Port and VLANS

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Last Modified: 2014-11-10
I have two Cisco SG300 Series switches that I'm trying to get setup. I only need a couple VLANS steep, but can seem to get the trunk port to work....a little over my head and not sure where to start.  I've created the VLANS, tagged them on my trunk ports, but cant even ping one switch from the other.
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Distinguished Expert 2018

Commented:
There is always same place to start check problem with trunk.

To check what ports are trunk ports, trunk mode, and what are allowed VLANs, and since it is dot1q encapsulation check is native VLAN same on both switches

#show interface trunk

If you still have no clue - post configuration of trunk ports , and show interface trunk command output from both switches.

Author

Commented:
Here's more info.  If anyone would be willing/ available I could setup a remote session if it's easier than trying to explain it all.

On both switches I have 3 VLANs 5, 10, 100, and then vlan 1, the cisco default.

5 and 100 I need to span across both switches.  On my trunk ports I have the clans tagged, except for vlan 1 (the default(


Here's the running config on the switches, this is just one, but both of them should be identical...

vlan database
vlan 5,10,100
exit
voice vlan oui-table add 0001e3 Siemens_AG_phone________
voice vlan oui-table add 00036b Cisco_phone_____________
voice vlan oui-table add 00096e Avaya___________________
voice vlan oui-table add 000fe2 H3C_Aolynk______________
voice vlan oui-table add 0060b9 Philips_and_NEC_AG_phone
voice vlan oui-table add 00d01e Pingtel_phone___________
voice vlan oui-table add 00e075 Polycom/Veritel_phone___
voice vlan oui-table add 00e0bb 3Com_phone______________
hostname switch714c71
no passwords complexity enable
username cisco password encrypted 7af78c911d5b48bea1dc2449d9d89513abeb4be5 privilege 15
!
interface vlan 1
 ip address 10.0.1.3 255.255.255.0
 no ip address dhcp
!
interface gigabitethernet1
 switchport mode access
!
interface gigabitethernet2
 switchport mode access
!
interface gigabitethernet3
 switchport mode access
!
interface gigabitethernet4
 switchport mode access
!
interface gigabitethernet5
 switchport mode access
!
interface gigabitethernet6
 switchport mode access
!
interface gigabitethernet7
 switchport mode access
!
interface gigabitethernet8
 switchport mode access
!
interface gigabitethernet9
 switchport mode access
!
interface gigabitethernet10
 switchport mode access
!
interface gigabitethernet11
 switchport mode access
!
interface gigabitethernet12
 switchport mode access
!
interface gigabitethernet13
 switchport mode access
!
interface gigabitethernet14
 switchport mode access
!
interface gigabitethernet15
 switchport mode access
!
interface gigabitethernet16
 switchport mode access
!
interface gigabitethernet17
 switchport mode access
!
interface gigabitethernet18
 switchport mode access
!
interface gigabitethernet19
 switchport mode access
!
interface gigabitethernet20
 switchport mode access
!
interface gigabitethernet21
 switchport mode access
!
interface gigabitethernet22
 switchport mode access
!
interface gigabitethernet23
 switchport mode access
!
interface gigabitethernet24
 switchport mode access
!
interface gigabitethernet25
 switchport mode access
!
interface gigabitethernet26
 switchport mode access
!
interface gigabitethernet28
 switchport trunk allowed vlan add 5,10,100
!
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Distinguished Expert 2018

Commented:
This should work - cause it sets trunk mode unconditionally on port

interface gigabitethernet28
 switchport mode trunk
 switchport nonegotiate  
 switchport trunk allowed vlan 1,5,10,100  ////////(not add VLAN - if those are only VLANS)

output down (code) tells a lot mode - auto/trunk/desirablestatus - non trunking/trunking
If both ends are configured as auto (I guess that's in your case) trunking will not work. Auto mode waits for other side to start trunk negotiation. Besides ping maybe don't work since in your case VLAN1 could be forbid on trunk (although default is allowed VLAN all - and when you add VLANs you really didn't do anything)
Switch# show interface trunk
Port          Mode      Encapsulation      Status       Native vlan
Fa0/28        auto          802.1q       not-trunking          1

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some oneNetwork Architect
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Top Expert 2014

Commented:
@Predrag - the SG-series switches use a slightly different code to standard IOS switches and the VLAN configuration is also slightly different.  The add command is required and it will just add it back into the code when the switch reboots.

You're right about the switchport mode trunk command though - these switches will set the port as a General port by default (IIRC) so it won't do automatic trunking by default.

Author

Commented:
Think I'm over my head on this one...I'll probably find some one local to come help me get it setup. I really appreciate your time, and I don't want to waste any more of it.

-B
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This one is on us!
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Author

Commented:
haha...so good news. I was able to figure it all out, and here come the strange part.

I had a bad port on the switch. It would light up fine, work as an access port, etc….but as soon as I set it to be the trunk it shut down and wouldn’t work.  To test and see if it was a hardware or settings issue, I copied its setting to another port and it worked instantly....really strange to say the least.

-B
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