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VLAN Configuration mismatch

Hello fellow networking geeks! 


I recently lost (system corrupted HDD) a configuration file to one of our Cisco SG-300-28 port managed switch and have had to rebuild a switch with less than great notes from the previous IT Manager. In my MDF I've got another SG300-50 (SWITCHA) sending traffic to the SG-300 28 port (SWITCHB). SWITCHA remains unchanged from the original setup, configuration is still correct  on that, SWITCHB is the one i need help with.


SWITCHA - sending VLAN1 & VLAN100 trunk to SWITCHB Trunk which has the same VLANS Tagged on the trunk. I've tagged VLAN100 to port 18 but I am unable to reach my cameras like i did before. See below my basic description. I can provide more details just let me know. 



VLAN1 default - VLAN

VLAN100 - Surveillance Cameras

VLAN1 & 100 are tagged on trunk port 51

Trunk port 51 is connected via fiber to SWITCHB



VLAN1 & VLAN100 is tagged on trunk port 28

Port18 is tagged with VLAN1 & VLAN100 and is set to GENERAL mode. 


I cannot ping within VLAN100 to any of my cameras on that subnet anymore. I know its something to do either with the way the VLAN is configured on the port or the trunk, or both. I just havent been able to crack it yet. Any ideas? :) 

Everyone's tags (6)
VIP Advisor

Re: VLAN Configuration mismatch

Hi there,

I don't know how you'd check it via the GUI, but via the CLI can you confirm that the following configuration lines are present on both switchports which make up the trunk link:


switch port encapsulation dot1q
switchport mode trunk



Re: VLAN Configuration mismatch

Hi Seb,


I read in another thread on the community that: This is normal. SG300 switch doesn't support ISL protocol, so there is no need in the command "switchport trunk encapsulation <trunk_protocol>". All trunk interfaces use dot1q to encapsulate ethernet frames on SG300.


To answer the second question of what mode its on: its on TRUNK mode on ge28

VIP Advisor

Re: VLAN Configuration mismatch

OK. So when you say you can't ping. Where are you situated? Pinging from switchB? Connected to switchA on VLAN1 or VLAN100 ?

Rising star

Re: VLAN Configuration mismatch


run this command on your port trunk (port that connected both switch A and B):
switchport mode trunk
switchport trunk allowed vlan 1,100

run this command on your port that you connecting your cameras:
switchport mode access
switchport access vlan 100

Best regards.
Jaderson Pessoa
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VIP Advisor

Re: VLAN Configuration mismatch


I have never had exposure to these switches however - Does the new switch have the L2 vlans propagated in its vtp database and make sure its running as a host switch meaning disable ip routing is enabled.

Swtch A/B
sh int trunk
sh vlan brief


Switch B
no ip routing

kind regards

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