native vlan question
in [Cisco]
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From: aaabbb16 on 15 Apr 2008 03:51 A lot of people ask native vlan question. I think using "vlan dot1q tag native" should eliminate this question. at least for sw---sw connection. (all tagged just like isl) I may not fully understand what's purpose why cisco make "native vlan". Some article say because of backward compatible with 802.3. Can anyone give an example? TIA, st
From: Trendkill on 15 Apr 2008 07:13 On Apr 15, 3:51 am, aaabb...(a)hotmail.com wrote: > A lot of people ask native vlan question. > I think using "vlan dot1q tag native" should eliminate this question. > at least for sw---sw connection. (all tagged just like isl) > I may not fully understand what's purpose why cisco make "native > vlan". > Some article say because of backward compatible with 802.3. > Can anyone give an example? > > TIA, > st Here are some good posts on this topic. Probably better than one of us typing up several paragraphs. The second article explains native vlan / vlan 1, and management interface concerns. http://www.velocityreviews.com/forums/t30335-native-vlan.html http://www.velocityreviews.com/forums/t40938-native-and-management-vlan-quotvlan-1quot.html
From: aaabbb16 on 15 Apr 2008 13:07 On 4ÔÂ15ÈÕ, ÉÏÎç4ʱ13·Ö, Trendkill <jpma...(a)gmail.com> wrote: > On Apr 15, 3:51 am, aaabb...(a)hotmail.com wrote: > > > A lot of people ask native vlan question. > > I think using "vlan dot1q tag native" should eliminate this question. > > at least for sw---sw connection. (all tagged just like isl) > > I may not fully understand what's purpose why cisco make "native > > vlan". > > Some article say because of backward compatible with 802.3. > > Can anyone give an example? > > > TIA, > > st > > Here are some good posts on this topic. Probably better than one of > us typing up several paragraphs. The second article explains native > vlan / vlan 1, and management interface concerns. > > http://www.velocityreviews.com/forums/t30335-native-vlan.htmlhttp://www.velocityreviews.com/forums/t40938-native-and-management-vl... Still confuse something.
From: stephen on 15 Apr 2008 16:13 <aaabbb16(a)hotmail.com> wrote in message news:123637df-5ec8-499a-a32c-cef68e1e21b4(a)z24g2000prf.googlegroups.com... > A lot of people ask native vlan question. > I think using "vlan dot1q tag native" should eliminate this question. > at least for sw---sw connection. (all tagged just like isl) > I may not fully understand what's purpose why cisco make "native > vlan". cisco didnt invent this - it is part of 802.1Q. > Some article say because of backward compatible with 802.3. i suggest you try to find the standard and read around that, maybe start at www.ieee.org AFAIR some of the standards docs are without charge for Ethernet. > Can anyone give an example? there are 2 Qs to think about. 1. set a port to be tagged - what do you do with a packet that arrives with no tag? the 2 common answers are to throw it away, or to put it into some sort of "default VLAN" - that is what untagged means for incoming packets. not putting a tag on outbound packets form that VLAN on that port allows 2 way comms. this sounds silly - but it is what often needs to happen when you hook up an unconfigured device to set it up. 2. what happens when you want to split up 2 streams of packets on a port? sometimes you have a device that will add its own stream of packets to a set it gets from elsewhere - the classic case is an IP phone where there is a plug on the phone to connect a PC. - Pcs dont normally send tagged frames, and the 3 port bridge in the phone doesnt have the horsepower to wrap a tag around every packet. - but you want the phone traffic kept separate from PC (security, QoS and so on). So - pass the PC packet thru untagged, and tag the phone traffic. At the switch the PC "stuff" is untagged and goes into the native VLAN, phone traffic is tagged and goes into a different VLAN. > > TIA, > st > -- Regards stephen_hope(a)xyzworld.com - replace xyz with ntl
From: aaabbb16 on 15 Apr 2008 23:31
On 4ÔÂ15ÈÕ, ÏÂÎç1ʱ13·Ö, "stephen" <stephen_h...(a)xyzworld.com> wrote: > <aaabb...(a)hotmail.com> wrote in message > > news:123637df-5ec8-499a-a32c-cef68e1e21b4(a)z24g2000prf.googlegroups.com... > > > A lot of people ask native vlan question. > > I think using "vlan dot1q tag native" should eliminate this question. > > at least for sw---sw connection. (all tagged just like isl) > > I may not fully understand what's purpose why cisco make "native > > vlan". > > cisco didnt invent this - it is part of 802.1Q. > > > Some article say because of backward compatible with 802.3. > > i suggest you try to find the standard and read around that, > maybe start atwww.ieee.org > > AFAIR some of the standards docs are without charge for Ethernet. > > > Can anyone give an example? > > there are 2 Qs to think about. > > 1. set a port to be tagged > - what do you do with a packet that arrives with no tag? > > the 2 common answers are to throw it away, or to put it into some sort of > "default VLAN" - that is what untagged means for incoming packets. > > not putting a tag on outbound packets form that VLAN on that port allows 2 > way comms. > > this sounds silly - but it is what often needs to happen when you hook up an > unconfigured device to set it up. > > 2. what happens when you want to split up 2 streams of packets on a port? > > sometimes you have a device that will add its own stream of packets to a set > it gets from elsewhere > - the classic case is an IP phone where there is a plug on the phone to > connect a PC. > - Pcs dont normally send tagged frames, and the 3 port bridge in the phone > doesnt have the horsepower to wrap a tag around every packet. > - but you want the phone traffic kept separate from PC (security, QoS and > so on). > > So - pass the PC packet thru untagged, and tag the phone traffic. > At the switch the PC "stuff" is untagged and goes into the native VLAN, > phone traffic is tagged and goes into a different VLAN. > > > TIA, > > st > > -- > Regards > > stephen_h...(a)xyzworld.com - replace xyz with ntl Thanks, For "Some article say because of backward compatible with 802.3" they may think far end is Hub or switch/bridge which does not support 802.3, right? One more question, when a access port receive a untag frame, does it add a 802.1q tag or some other tag to make sure it can go same vlan inside of this switch? |