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C3750-Native Vlan

Platform : C3750

IOS : c3750-ipservices-mz.122-25.SEB4

Question 1 : How can I put native vlan tagging disabled, seems to be enabled by default, no vlan dot1q tag native .....

Question 2 : What s better tag enabled or disabled ? ( versus c6k 122-33SRA1 )

Best Regards

Francois

4 REPLIES
Cisco Employee

Re: C3750-Native Vlan

Hi Francois,

I don't think it is possible on 3750 platform. AFAIK each trunk have to have one native vlan if configured for dot1q.

If you choose the encapsulation as ISL then you can get rid of native vlan.

Also in dot1q if you want all your traffic to be tagged then workaround can be to have one vlan which is not a part of your network and make that vlan as native on trunk.

Coming on your question 2 it depends on your network requirement to decide which vlan should be tagged or untagged. On trunk interface you can have only one vlan as untagged.

HTH

Ankur

Re: C3750-Native Vlan

The default is to send all traffic for the native vlan untagged. This is to comply with the dot1Q standard. Having one vlan untagged on a trunk allows compatability with non-dot1Q capable devices on the same wire.

Please check the URL below for more details:

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_guide_chapter09186a0080502455.html

Regards,

Leo

Re: C3750-Native Vlan

Hi Francois,

On 3750 switch you use global configuration command " vlan dot1q tag native" to enable the tagging of native vlan frames on all the IEEE802.1q enables trunk ports.

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3750/12225sed/cr/cli3.htm#wp2699666

It depends on individual choice but in my opinion it better to have all them tagged.

HTH, Pleare rate if it does.

-amit singh

New Member

Re: C3750-Native Vlan

Hi,

Thanks to all.

1 no vlan dot1q tag native is nt efficient on c3750: show interf. gbEth1/0/1 switchport says that Adm.Native Vlan Tagging : enabled.

2 subjacent problem follows :

on the the c3750 I ve 3 vlans (with the vl1 )

VLX + interface VlanX ( Ip_gateway )

VLY+ interface VlanY ( Ip_gateway )

Interf. GbEth1/0/1 trunk, 8021q,allowed vlan 800 ( interconnection ), same thing on the c6k,with an ip-address for each in the interco VLan ( default ip route on the c3750 ) result

of trunking is OK for VLX ( internet and so on )and without results for VLY

I m reading DOC ID 10558. Regards.Francois

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