Native VLAN

[karl.jones]

Hi All

Just a quick question ... ive always left vlan 1 as the management vlan but also put pc's and servers on that network as there has never been a need for multiple vlans. How important is it to keep general network traffic off the management vlan and what potential problems could it cause having pc's and servers on the management vlan. Just interested.

Regards

[mfaust]

In a lightly loaded network there won't be any problem. If your network is heavily loaded, there is the possibility that management messages could be at risk. As a precaution, I always create at least one VLAN for user data and keep VLAN 1 clear for network messages.

[karl.jones]

Thankyou for that, I will follow you advice here .... what about if just have vlan 1 with pc's and servers and no other vlans in the switching domain ... is there an issue with the management messages if you havent configured a vtp domain or any additional vlans. Your thoughts on this would be appreciated.

Thanks again

[mfaust]

In addition to VTP, VLAN 1 is used by CDP, DTP and PAgP. Interface sc0 is also a member of VLAN 1 and don't forget STP BPDUs. Even if you prune VLAN 1 from trunks, management traffic is tagged VLAN 1. Only user data traffic is pruned from VLAN 1. All of these bits of information are a clue. Cisco wants the user data on a VLAN seperate from the management traffic. A quote from Cisco: "Control plane data on VLAN 1 should be kept seperate from the user data to symplify troubleshooting and maximize available CPU cycles". Also, since sc0 is on VLAN 1, you can troubleshoot and manage your switches logically 'out of band' (sc0 is on a different subnet than user data).

[karl.jones]

Thanks Mike ... I will follow this advice. The reason I ask the 2nd question was that I recently put a gigabit backbone in recently but in a flat topology and created no vlans .... just an ethernet connection through to a router. I guess I will have to review this in the future when I get a minute,

Thanks again