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wifi native vlan 0 >>> wired native vlan 1 >>> wifi native vlan 0...

jonathan.maxwell
Beginner
Beginner

Hello.

In many APs and WLCs the default native vlan is 0. In wired networks the default native vlan is 1. If Wifi control traffic traverses the circuit...

Wifi native vlan 0 >>> wired native vlan 1 >>> Wifi native vlan 0

... will traffic be dropped between the wired and wireless networks?

 

To me, the issue is whether the medium border switches think vlan0 is the same as vlan1, and thus allows the untagged traffic straight through. It seems the switch IOS needs to understand an implicit demarcation between the wireless and wired network vlan boundries for this to work. If not, the IOS would need code to say vlan1 = vlan 0 (or something to that effect). 

What are your thoughts regarding this situation?

Thank you.

 

 

2 Accepted Solutions

Accepted Solutions

jonathan.maxwell
Beginner
Beginner

Hi Flavio. Thanks for the reply.

 

I just found my answer. It seems to help to google questions before bothering the Cisco community! Anyway, I hope the community found this topic edifying...

"The VLAN ID 0 is used when a device needs to send priority-tagged frames but does not know in which particular VLAN it resides. The basic Ethernet frame does not have any priority field. The priority bits, also called CoS bits (Class of Service) are a part of 802.1Q VLAN tag. Therefore, a device needing to add a CoS marking to its frames has to insert a 802.1Q tag into each frame. However, even though this device may be capable of adding 802.1Q tags into its frames, it may not know in what VLAN it currently resides.

This is where the VLAN ID 0 comes in. A device that sends CoS-marked frames can insert a 802.1Q tag into a frame, use the VLAN ID 0 and set the CoS marking appropriately. When a VLAN-aware switch receives this frame, the VLAN ID 0 tells it: "Put the frame in the ordinary access VLAN of the port as if it was untagged, however, process the CoS field accordingly." In other words, the VLAN ID 0 represents the access - or the native - VLAN of the receiving port, whatever VLAN that might be."

View solution in original post

Rich R
VIP Advisor VIP Advisor
VIP Advisor

FYI: Table 9-2—Reserved VID values of IEEE 802.1Q standard section 9.6 VLAN Tag Control Information (TCI)

"0 The null VID. Indicates that the tag header contains only priority information; no VID is present in the frame. This VID value shall not be configured as a PVID or a member of a VID Set, or configured in any FDB entry, or used in any Management operation."

 

It's purely a mechanism for attaching a COS setting to an UNTAGGGED frame - it is NOT a VLAN ID.

So there is no such thing as "native vlan 0".

___________________________________________
TAC recommended codes for AireOS WLC's
Best Practices for AireOS WLC's
TAC recommended codes for 9800 WLC's
Best Practices for 9800 WLC's
Cisco Wireless compatibility matrix
Field Notice: FN-72424 Later Versions of WiFi 6 APs Fail to Join WLC - Software Upgrade Recommended
WARNING - see CSCwd37092 Throughput degraded after upgrading to code 8.10.181.0/17.3.6 - 2800/3800/4800 series
- The fix for CSCwd37092 is now released in 8.10.183.0 and
- For IOS-XE 17.3.6 select controller model, go to IOS XE Software AP Service Pack, select CSCwd40096 17.3.6 APSP2
Field Notice: FN-63942 Lightweight APs and WLCs Fail to Create CAPWAP Connections Due to Certificate
                      Expiration - Software Upgrade Recommended
Field Notice: FN-72524 - During Software Upgrade/Downgrade IOS APs Might Remain in Downloading State
                     After 4 Dec 2022 Due to Certificate Expiration - Fixed in 8.10.183.0 and 17.3.6 APSP5 (APSP_CSCwd83653)
                     Also fixed in 8.5.182.7 (8.5 mainline) and 8.5.182.105 (8.5 IRCM) if you can't upgrade to 8.10
                     Note that 8.10.181.0 and 8.10.182.0 have been deferred (withdrawn) and are effectively unsupported by Cisco
___________________________________________
Richard R

View solution in original post

5 Replies 5

Flavio Miranda
Advisor
Advisor

Hi

   Dont follow you.  First, if native vlan is meant to be untagged, how "0" and "1" could be important if "0" and "1" is a tag?

Second, where this native vlan 0 came from?  And why a Wired network need to worry about a wireless device if, in the point the touch each other, they will be both Wired?

VLAN native 0? there is no such as this I think.

I follow your previous post, still face issue with new SW?

friend 
image the WLC as client, 
AP"FLEX"-WLC there is CAPWAP tunnel, this tunnel is from AP ip to management IP of WLC 
AP IP can be in any subnet 
management IP of WLC can be in any subnet

SUBNET meaning VLAN 

NOW 
the client connect to AP get IP from subnet not config in AP because there is tunnel.
the client subnet in WLC side.
WLC connect to SW through trunk 
trunk allow 
management VLAN  and all client VLAN 

the SW also connect to wire device they can connect to wireless if they are in same subnet.

jonathan.maxwell
Beginner
Beginner

Hi Flavio. Thanks for the reply.

 

I just found my answer. It seems to help to google questions before bothering the Cisco community! Anyway, I hope the community found this topic edifying...

"The VLAN ID 0 is used when a device needs to send priority-tagged frames but does not know in which particular VLAN it resides. The basic Ethernet frame does not have any priority field. The priority bits, also called CoS bits (Class of Service) are a part of 802.1Q VLAN tag. Therefore, a device needing to add a CoS marking to its frames has to insert a 802.1Q tag into each frame. However, even though this device may be capable of adding 802.1Q tags into its frames, it may not know in what VLAN it currently resides.

This is where the VLAN ID 0 comes in. A device that sends CoS-marked frames can insert a 802.1Q tag into a frame, use the VLAN ID 0 and set the CoS marking appropriately. When a VLAN-aware switch receives this frame, the VLAN ID 0 tells it: "Put the frame in the ordinary access VLAN of the port as if it was untagged, however, process the CoS field accordingly." In other words, the VLAN ID 0 represents the access - or the native - VLAN of the receiving port, whatever VLAN that might be."

Rich R
VIP Advisor VIP Advisor
VIP Advisor

FYI: Table 9-2—Reserved VID values of IEEE 802.1Q standard section 9.6 VLAN Tag Control Information (TCI)

"0 The null VID. Indicates that the tag header contains only priority information; no VID is present in the frame. This VID value shall not be configured as a PVID or a member of a VID Set, or configured in any FDB entry, or used in any Management operation."

 

It's purely a mechanism for attaching a COS setting to an UNTAGGGED frame - it is NOT a VLAN ID.

So there is no such thing as "native vlan 0".

___________________________________________
TAC recommended codes for AireOS WLC's
Best Practices for AireOS WLC's
TAC recommended codes for 9800 WLC's
Best Practices for 9800 WLC's
Cisco Wireless compatibility matrix
Field Notice: FN-72424 Later Versions of WiFi 6 APs Fail to Join WLC - Software Upgrade Recommended
WARNING - see CSCwd37092 Throughput degraded after upgrading to code 8.10.181.0/17.3.6 - 2800/3800/4800 series
- The fix for CSCwd37092 is now released in 8.10.183.0 and
- For IOS-XE 17.3.6 select controller model, go to IOS XE Software AP Service Pack, select CSCwd40096 17.3.6 APSP2
Field Notice: FN-63942 Lightweight APs and WLCs Fail to Create CAPWAP Connections Due to Certificate
                      Expiration - Software Upgrade Recommended
Field Notice: FN-72524 - During Software Upgrade/Downgrade IOS APs Might Remain in Downloading State
                     After 4 Dec 2022 Due to Certificate Expiration - Fixed in 8.10.183.0 and 17.3.6 APSP5 (APSP_CSCwd83653)
                     Also fixed in 8.5.182.7 (8.5 mainline) and 8.5.182.105 (8.5 IRCM) if you can't upgrade to 8.10
                     Note that 8.10.181.0 and 8.10.182.0 have been deferred (withdrawn) and are effectively unsupported by Cisco
___________________________________________
Richard R
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