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Purple

Native vlan on Cat OS switches

What exactly is the importance of the native vlan on these switches , tried to get a understanding by looking across CCO but it still isn't clear to me . Should it be left in vlan 1 or should it be changed . What are the pro's or cons of leaving it in vlan 1 . We are currently having a problem where people are getting dropped when doing file transfers and the native vlan is a vlan that is supernetted and has 800-1000 users on this particular , should the native vlan be set to this ? I'm thinking not but would like hear some opinions on this . What we are also seeing is large amounts of xmit errors on the ports (buffers being overrun) also . This is a trunked environment (8021Q) and is run across several Cat4000's and we are seeing these xmit errors on all these switches for this supernetted subnet . What might cause this , unable to pin it down so far . It's not a port duplex or speed issue all that has been checked .

2 REPLIES
Cisco Employee

Re: Native vlan on Cat OS switches

any vlan can be used as a native vlan.

However it is recommended not to use the native vlan as a data vlan.

In other words, do not attach devices to the native vlan.

Native vlan should be only used byt the switches for management traffic.

Because vlan 1 is also the default vlan when you enable a port, it is recommended to change the native vlan to something else than 1 (to be sure no devices is attached to it).

If you have a lot of xmit error, did you try to replace the cable and/or the port ?

Purple

Re: Native vlan on Cat OS switches

It's not a port problem because we are seeing these errors across many different ports across multiple switches but they are all in the same vlan , I'm suspecting that we are seeing a device or devices that are broadcasting or arping the heck out of the subnet which is overruning the xmit buffers on all these ports . this is sort of a test environment so it could be almost anything . Anything else we can look for . We do have a sniffer available so we will be looking at that shortly .

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