(Another) Native VLAN tagging question..
I have completed CCNA 3 course and am in 4 right now. I am still confused about VLAN native commands such as
sw tr na vl xxx
When this is on a trunk port, what does it mean?
Thanks....
"So does that mean that before the packet goes onto the trunk link it is put into the native VLAN then when it exits the trunk link (on the other side) it is stripped of the VLAN info? "
No, what your prior quotation decribed is what a switch should do with untagged frames received on a port defined as a VLAN trunk.
The VLAN tags informs the switch what VLAN a frames belongs to when it is received on a VLAN trunk port, but without such a tag, how does the switch know the intended VLAN? It doesn't, from the frame itself. So, we can often configure a trunk port to place any untagged frames into one VLAN of our choice. In theory, once we define what VLAN untagged frames will be considered a member of, tagged frames, for that VLAN could also be accepted. Both should be treated the same by the receiving switch.
As for a switch sending packets out a VLAN trunk, normally you would expect all packets to be VLAN tagged although a switch might support sending one particular VLAN frames without tags to support a device, such as the PC described in your quotation, that doesn't understand how to process, or expect, tagged frames.
If you're wondering how this all comes to be, consider a PC that knows nothing about VLAN tags is connected to an IP phone which does (which connects to the network) and you want to place the two devices on different VLANs. As the PC traffic transits the phone could, in theory, wrap/unwrap the PC traffic with VLANs tags when working with the network switch. However, if the phone fails, you can design the IP phone hardware to keep the link good from PC to the network, but then the IP phone PC VLAN processing would be lost. So for that reason, and the reason, we might want to add/remove an IP phone "in front" of the PC, we want to continue to support untagged frames to/from the PC.
Altough the frames to the PC are untagged, since we can configure what VLAN untagged frame should be considered per port, we can have different PCs (on different ports) in different VLANs on the switch. (This is very similar to port based VLANs, but instead of being limited to one logical VLAN per port, we're limited to one untagged VLAN per port but can have multiple tagged VLANs per port.)
Similar Messages
-
Q-in-Q w/o Native VLAN tag question
Let's assume that we have Q-in-Q setup between 2 service provider switches. To run Q-in-Q we want to terminate a trunk into each tunnel port and enable native VLAN tagging to ensure that all customer VLAN's are tagged. In some cases we may have a customer that wants to connect their own equipment into the tunnel port on our switch, so it wouldn't actually be a trunk - it would be an access port. If this occurs then there is no inner VLAN tag, only an outer VLAN tag. Will tunnelling still function properly in this scenario?
actually this is not true... sorry Kishore
Tunneling still works and traffic within the SP core will be singled tagged (with the SP tag only).
However when you do this you need to be extremely careful specially if you use dot1q trunks in the core with native vlan within the customer range. You might end up in unexpected result in this case.
See an exmple of a possible issue you might see in this case:
http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_58_se/configuration/guide/swtunnel.html#wp1008635
The solution would be to tag native vlan in the SP core or use ISL trunks or use native vlans outside customer range or (logically) use trunk ports on CE device (still paying attention to native vlan though).
Riccardo -
Native VLAN tagging work-around?
Good Day!
Story here is that I am upgrading my 6500 Metro Ethernet core switch from CatOS to IOS and implementing several security components - one in question is implementing 'vlan dot1q tag native' global command on core switch. Most of my PE switches are 3550 series and are compatible with this configuration. The problem is that I also have several remote legacy 3508G switches that I need to support, and they will not accept this command.
Is anyone aware of a work-around config for these 3508s? So far have not found any help on CCO...
Thanks!Don't know if you can do this on a Cat6500 running IOS, but here's my idea:
Set the native VLAN on the 3508G end of the 802.1Q trunk to a VLAN that is not going to be used anywhere for access, and match the native VLAN specification on your 6500's corresponding interface. Then, remove that VLAN from the trunk at both ends.
The way I read it, on the 6500 the "vlan dot1q tag native" command would tag outgoing traffic on the native VLAN; and would drop all incoming traffic on the native VLAN that wasn't tagged. But none of that will matter, because removing that one VLAN from the allowed VLAN list on the trunk will leave you with only tagged VLAN traffic on the trunk from the 3508G. CDP will see that the native VLAN is set the same at each end (if you use CDP), so it won't flag any mismatches there. You just won't use the native VLAN on the trunk.
I'm doing something similar with CatOS on a 6509 and 2950G access switches. Setting native VLAN to 1 (the default) on both ends, which makes it untagged; and then removing VLAN 1 from the trunk on both sides, leaving me with only tagged traffic on the trunk.
Now, VLAN 1 is a special case, you can't remove it completely from the allowed VLAN list on a 2950G. The documentation refers to it as "minimizing" VLAN 1: CDP and VTP traffic will still pass over it, as will a couple of other Cisco-centric things; but no user traffic, and no STP BPDUs. Testing it today, I verified the CDP and VTP traffic work in both directions after I cleared VLAN 1 from the trunk and had only one customer VLAN, tagged, on it.
In your situation, you can't remove VLAN 1 at all from a 3508G XL trunk. So just pick another VLAN to throw away as the native VLAN that you remove from the trunk, and transmit VLAN1 tagged across it.
I think DTP uses the native VLAN; so the only drawback to my idea is that you have to manually set the trunk mode rather than letting the switches negotiate it out. (No problem for me, I set them all manually anyway.)
Hope this helps. -
Hello , We have 6513 Core Switch and WISM , If I ping from the access points subnet to the WISM IP address there is so many request time out and the number of Access Points registered is going up and down
In the core switch we are tagging the native Vlan as you can see below
CORE-SWITCH2#sh run | i tag
vlan dot1q tag native
and we don't have the command wism module 9 controller 1 native-vlan X because the native vlan is tagged
could this be the reason ? that its mandatory that the native VLAN is not tagged for the Cisco WISM configuration
your reply and feed back is highly appreciated
many thanksCisco recommends to TAG the management interface. Cisco use to state to configure the managment vlan as native. It makes it easier for QoS as well when all vlans are TAGGED.
What is key is all your WISMs managment interfaces need to be TAGGED or UNTAGGED. You cant have a mix.
How are yours set up ? -
Hi friends,
I attached a simple diagram which modelize my question.
As u will see in the sample diagram. I have two networks one has 192.168.1.0/23 as a network address and the other has 10.10.10.0 /24.
I wanna connect these two networks to ASA 5510. But i dont have enough interfaces so i have to use single interface. lets say E1. Also i have an unmanaged switch.
Here is the question: If i configured subinterfaces as E1.100 and E1.200 on ASA. Do i need to set the port on Switch which is connected to ASA as a trunk port? (well.. i couldnt do it... its unmanageable)
Is the following configuration enough to use for my question?
interface ethernet1.100
vlan 100
ip address 192.168.1.1 255.255.254.0
nameif networkA
interface ethernet1.200
vlan 200
ip address 10.10.10.1 255.255.255.0
nameif networkB
or do i need to set any port as trunk?
Thanks alot?You need trunk port on your switch anyway only one vlan (vlan 100 or vlan 200) can be transfered to ASA.
Over a trunk port you can transfer more than one VLAN traffic.
bye
FCS
Please rate me if I helped. -
Hi!
I have a particular installation on a customer site.
The management vlan is the number 1 (which is the native vlan) for the whole network and all the switches tag the native vlan.
So when I plug my AP on a port of a switch configured in trunk mode, it doesn't work.
How can I resolve this issue?
ThanksYes, you can specify the native VLAN, though I am not sure if that will enable tagging of that VLAN or not. You might have to try it yourself to see. See the following link for pictures of the pages in question.
http://www.cisco.com/en/US/products/ps6087/products_tech_note09186a0080736123.shtml#t12
Because I think it will require a reboot after enabling HREAP but before setting up VLAN support, you might need to set it as an access port while making the changes.
1. Do not use VLANs for your H-REAP deployment and set the access point switch ports as Access ports in the VLAN you want your users to be in. The AP will need an IP in the user VLAN, but that is not usually a problem. If you do not need multiple user VLANs from different SSIDs, this will be the easiest option.
2. Disable native VLAN tagging for the ports with APs with the command I listed above. -
Hi,
I cant figure out why this is showing on switches.
Core switch brc-k25-1 is using Native Vlan 1
Access switch c2-k25-5 is using Native Vlan 1
I get the following error message on the access switch:
Jun 27 08:57:40: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 171 on GigabitEthernet1/0/49 VLAN1.
Jun 27 08:57:40: %SPANTREE-2-BLOCK_PVID_PEER: Blocking GigabitEthernet1/0/49 on VLAN0171. Inconsistent peer vlan.
Jun 27 08:57:40: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking GigabitEthernet1/0/49 on VLAN0001. Inconsistent local vlan.
Jun 27 08:57:40: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down
Jun 27 08:57:55: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking GigabitEthernet1/0/49 on VLAN0171. Port consistency restored.
Jun 27 08:57:55: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking GigabitEthernet1/0/49 on VLAN0001. Port consistency restored.
Jun 27 08:57:55: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up
Because of the error, I cannot login to the access switch using the native Vlan IP Address.
brc-k25-1 config:
interface GigabitEthernet3/2
description c2-k25-5
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,146,171
switchport mode trunk
logging event link-status
logging event trunk-status
qos trust dscp
tx-queue 1
bandwidth percent 69
tx-queue 2
bandwidth percent 1
tx-queue 3
bandwidth percent 15
priority high
tx-queue 4
bandwidth percent 15
end
brc-k25-1#sh interfaces gigabitEthernet 3/2 switchport
Name: Gi3/2
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: 1,146,171
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
interface Vlan1
ip address 172.27.40.254 255.255.255.02
ip access-group vlan1out out
==================================================
c2-k25-5 config:
c2-k25-5#sh cdp ne
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
brc-k25-1 Gig 1/0/49 138 R S I WS-C4506 Gig 3/2
interface GigabitEthernet1/0/49
description brc-k25-5
switchport trunk allowed vlan 1,146,171
switchport mode trunk
interface Vlan1
ip address 172.27.40.18 255.255.255.0
interface Vlan146
ip address 172.31.146.1 255.255.255.0
c2-k25-5#sh interfaces gigabitEthernet 1/0/49 switchport
Name: Gi1/0/49
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: 1,146,171
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: noneThanks for the replies.
I did remove the ACL from the VLAN1 but nothing change. Also the allowed VLAN1 was not included in the trunk allowed before, same result as now.
Jun 30 09:06:40: %SPANTREE-2-RECV_PVID_ERR: Received BPDU with inconsistent peer vlan id 171 on GigabitEthernet1/0/49 VLAN1.
Jun 30 09:06:40: %SPANTREE-2-BLOCK_PVID_PEER: Blocking GigabitEthernet1/0/49 on VLAN0171. Inconsistent peer vlan.
Jun 30 09:06:40: %SPANTREE-2-BLOCK_PVID_LOCAL: Blocking GigabitEthernet1/0/49 on VLAN0001. Inconsistent local vlan.
Jun 30 09:06:41: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down
Jun 30 09:06:55: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking GigabitEthernet1/0/49 on VLAN0171. Port consistency restored.
Jun 30 09:06:55: %SPANTREE-2-UNBLOCK_CONSIST_PORT: Unblocking GigabitEthernet1/0/49 on VLAN0001. Port consistency restored.
Jun 30 09:06:56: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up
We have multiple switches attached to the brc-k25-1 and only 2 switches are affected using VLAN1 management. I had to create another VLAN ID so that I can use that IP Address to SSH. Very weird problem. -
Vlan tag issue with Nexus 4001 in IBM Blade Centre
Hi
I have a DC architecture with a pair of Nexus 7010's running 3 VDC's (Core/Aggregation/Enterprise). I have at the edge Nexus 5548's which connect to back to the Aggregation VDC. Also connecting back to the Aggregation VDC is an IBM Blade Chassis which has a Nexus 4001i in slots 7 and slot 9. These blade servers are running ESXi 4.0 and are mapped to the Nexus 4001 blade switch.
I had set up the Native VLAN as VLAN 999 which connects up to the ESXi host and I am trunking up multiple VLANS for the Virtual Machines.
The problem I have is that VM's in all VLANS except the ESXi host VLAN (VLAN 10) cannot see their default gateway, and I suspect that there is an issue with the VLAN tag going up to the ESXi host. I have read enough documentation to suggest that this is where the issue is.
My Nexus 4001 interface configuration is below
interface Ethernet1/1
switchport mode trunk
switchport trunk native vlan 999
switchport trunk allowed vlan 10,30,40-41,60-62,90,96,999
spanning-tree port type edge trunk
speed auto
The Aggregation VDC on the Nexus 7010 is the default gateway for all these VLANS.
I also noted that the Nexus 5000 and Nexus 7000 supports the command vlan dot1q tag native command yet the Nexus 4000 doesn't seem to support this. Any assistance would be useful
Thanks
GregYour configuration on the N4K looks correct. You shouldn't use vlan dot1q tag native commands on your N7Ks and N5Ks. Native VLAN tagging is really for QinQ (dot1q tunneling).
My only suggestion is check your configuration of the vSwitch in the ESXi host and the host network profile.
Regards,
jerry -
Native Vlan LWAP to Controller
Hi guys,
I had a LWAP connected to a switch trunk port:
Port Vlans allowed on trunk
Fa1/1 1-4094
LWAP joined the WLC, then I switched it to FlexConnect Mode. I enabled Vlan Support and used Vlan 1 as Native Vlan.
Knowing exactly site's SSID I went to the switch and "secured the config":
interface fa1/1
switchport trunk allowed vlan none
switchport trunk allowed vlan add 5, 10
show interfaces FastEthernet 1/1 switchport
Name: Fa1/1
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Trunking VLANs Enabled: 5, 10
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
I did this, assuming that LWAP will communicate with the controller on NATIVE Vlan 1, while vlans 5 and 10 had to be mapped/used to the two site's SSIDs. As you probably assume LWAP got disconnected from the controller.
I had to switchport trunk allowed vlan add 1 and finally things got as it were.
Why does native vlan had to be also allowed on the tagged Vlan list?Florin -
Vlan 1 had to also be allowed because of the command you issued:
switchport trunk allowed vlan none
This command effectively prevents any vlans (tagged or untagged) from passing across the trunk link. Be aware the trunk link will remain in an On state even though you have blocked all vlans from passing through it. So think of the switchport trunk allowed set of commands as a block/allow set of rules that exists independently of the configuration requirements to create a trunk link such as one native vlan being established/encapsulation being set/negotiation being set.
Regards,
Justin
P.S. here is a link that will help explain it in more detail https://supportforums.cisco.com/document/11836/how-define-vlans-allowed-trunk-link -
Various questions on uplink profiles, CoS, native VLAN, downlink trunking
I will be using vPC End Host Mode with MAC-pinning. I see I can further configure MAC-Pinning. Is this required or will it automatically forward packets by just turning it on? Is it also best not to enable failover for the vnics in this configuration? See this text from the Cisco 1000V deployment Guide:
Fabric Fail-Over Mode
Within the Cisco UCS M71KR-E, M71KR-Q and M81KR adapter types, the Cisco Unified Computing System can
enable a fabric failover capability in which loss of connectivity on a path in use will cause remapping of traffic
through a redundant path within the Cisco Unified Computing System. It is recommended to allow the Cisco Nexus
1000V redundancy mechanism to provide the redundancy and not to enable fabric fail-over when creating the
network interfaces within the UCS Service Profiles. Figure 3 shows the dialog box. Make sure the Enable Failover
checkbox is not checked."
What is the 1000V redundancy?? I didn't know it has redundancy. Is it the MAC-Pinning set up in the 1000V? Is it Network State Tracking?
The 1000V has redundancy and we can even pin VLANs to whatever vNIC we want. See Cisco's Best Practices for Nexus 1000V and UCS.
Nexus1000V management VLAN. Can I use the same VLAN for this and for ESX-management and for Switch management? E.g VLan 3 for everything.
According to the below text (1000V Deployment Guide), I can have them all in the same vlan:
There are no best practices that specify whether the VSM
and the VMware ESX management interface should be on the same VLAN. If the management VLAN for
network devices is a different VLAN than that used for server management, the VSM management
interface should be on the management VLAN used for the network devices. Otherwise, the VSM and the
VMware ESX management interfaces should share the same VLAN.
I will also be using CoS and Qos to prioritize the traffic. The CoS can either be set in the 1000V (Host control Full) or per virtual adapter (Host control none) in UCS. Since I don't know how to configure CoS on the 1000V, I wonder if I can just set it in UCS (per adapter) as before when using the 1000V, ie. we have 2 choices.
Yes, you can still manage CoS using QoS on the vnics when using 1000V:
The recommended action in the Cisco Nexus 1000V Series is to assign a class of service (CoS) of 6 to the VMware service console and VMkernel flows and to honor these QoS markings on the data center switch to which the Cisco UCS 6100 Series Fabric Interconnect connects. Marking of QoS values can be performed on the Cisco Nexus 1000V Series Switch in all cases, or it can be performed on a per-VIF basis on the Cisco UCS M81KR or P81E within the Cisco Unified Computing System with or without the Cisco Nexus 1000V Series Switch.
Something else: Native VLANs
Is it important to have the same native VLAN on the UCS and the Cisco switch? And not to use the default native VLAN 1? I read somewhere that the native VLAN is used for communication between the switches and CDP amongst others. I know the native VLAN is for all untagged traffic. I see many people set the ESXi management VLAN as native also, and in the above article the native VLAN (default 1) is setup. Why? I have been advised to leave out the native VLAN.
Example:Will I be able to access a VM set with VLAN 0 (native) if the native VLAN is the same in UCS and the Cisco switch (Eg. VLAN 2)? Can I just configure a access port with the same VLAN ID as the native VLAN, i.e 2 and connect to it with a PC using the same IP network address?
And is it important to trunk this native VLAN? I see in a Netapp Flexpod config they state this: "This configuration also leverages the native VLAN on the trunk ports to discard untagged packets, by setting the native VLAN on the port channel, but not including this VLAN in the allowed VLANs on the port channel". But I don't understand it...
What about the downlinks from the FI to the chassis. Do you configure this as a port channel also in UCS? Or is this not possible with the setup described here with 1000V and MAC-pinning.
No, port channel should not be configured when MAC-pinning is configured.
[Robert] The VSM doesn't participate in STP so it will never send BPDU's. However, since VMs can act like bridges & routers these days, we advise to add two commands to your upstream VEM uplinks - PortFast and BPDUFilter. PortFast so the interface is FWD faster (since there's no STP on the VSM anyway) and BPDUFilter to ignore any received BPDU's from VMs. I prefer to ignore them then using BPDU Gaurd - which will shutdown the interface if BPDU's are received.
-Are you thinking of the upstream switch here (Nexus, Catalyst) or the N1kV uplink profile config?
Edit: 26 July 14:23. Found answers to many of my many questions...Answers inline.
Atle Dale wrote:
Something else: Native VLANsIs it important to have the same native VLAN on the UCS and the Cisco switch? And not to use the default native VLAN 1? I read somewhere that the native VLAN is used for communication between the switches and CDP amongst others. I know the native VLAN is for all untagged traffic. I see many people set the ESXi management VLAN as native also, and in the above article the native VLAN (default 1) is setup. Why? I have been advised to leave out the native VLAN.[Robert] The native VLAN is assigned per hop. This means between the 1000v Uplinks port profile and your UCS vNIC definition, the native VLAN should be the same. If you're not using a native VLAN, the "default" VLAN will be used for control traffic communication. The native VLAN and default VLAN are not necessarily the same. Native refers to VLAN traffic without an 802.1q header and can be assigned or not. A default VLAN is mandatory. This happens to start as VLAN 1 in UCS but can be changed. The default VLAN will be used for control traffic communication. If you look at any switch (including the 1000v or Fabric Interconnects) and do a "show int trunk" from the NXOS CLI, you'll see there's always one VLAN allowed on every interface (by default VLAN 1) - This is your default VLAN.Example:Will I be able to access a VM set with VLAN 0 (native) if the native VLAN is the same in UCS and the Cisco switch (Eg. VLAN 2)? Can I just configure a access port with the same VLAN ID as the native VLAN, i.e 2 and connect to it with a PC using the same IP network address?[Robert] There's no VLAN 0. An access port doesn't use a native VLAN - as its assigned to only to a single VLAN. A trunk on the other hand carries multiple VLANs and can have a native vlan assigned. Remember your native vlan usage must be matched between each hop. Most network admins setup the native vlan to be the same throughout their network for simplicity. In your example, you wouldn't set your VM's port profile to be in VLAN 0 (doens't exist), but rather VLAN 2 as an access port. If VLAN 2 also happens to be your Native VLAN northbound of UCS, then you would configured VLAN 2 as the Native VLAN on your UCS ethernet uplinks. On switch northbound of the UCS Interconnects you'll want to ensure on the receiving trunk interface VLAN 2 is set as the native vlan also. Summary:1000v - VM vEthernet port profile set as access port VLAN 21000v - Ethernet Uplink Port profile set as trunk with Native VLAN 2UCS - vNIC in Service Profile allowing all required VLANs, and VLAN 2 set as NativeUCS - Uplink Interface(s) or Port Channel set as trunk with VLAN 2 as Native VLANUpstream Switch from UCS - Set as trunk interface with Native VLAN 2From this example, your VM will be reachable on VLAN 2 from any device - assuming you have L3/routing configured correctly also.And is it important to trunk this native VLAN? I see in a Netapp Flexpod config they state this: "This configuration also leverages the native VLAN on the trunk ports to discard untagged packets, by setting the native VLAN on the port channel, but not including this VLAN in the allowed VLANs on the port channel". But I don't understand it...[Robert] This statement recommends "not" to use a native VLAN. This is a practice by some people. Rather than using a native VLAN throughout their network, they tag everything. This doesn't change the operation or reachability of any VLAN or device - it's simply a design descision. The reason some people opt not to use a native VLAN is that almost all switches use VLAN 1 as the native by default. So if you're using the native VLAN 1 for management access to all your devices, and someone connects in (without your knowing) another switch and simply plug into it - they'd land on the same VLAN as your management devices and potentially do harm.What about the downlinks from the FI to the chassis. Do you configure this as a port channel also in UCS? Or is this not possible with the setup descrived here with 1000V and MAC-pinning.[Robert] On the first generation hardware (6100 FI and 2104 IOM) port channeling is not possible. With the latest HW (6200 and 2200) you can create port channels with all the IOM - FI server links. This is not configurable. You either tell the system to use Port Channel or Individual Links. The major bonus of using a Port Channel is losing a link doesn't impact any pinned interfaces - as it would with individual server interfaces. To fix a failed link when configured as "Individual" you must re-ack the Chassis to re-pinn the virtual interfaces to the remaining server uplinks. In regards to 1000v uplinks - the only supported port channeling method is "Mac Pinning". This is because you can't port channel physical interfaces going to separate Fabrics (one to A and one to B). Mac Pinning gets around this by using pinning so all uplinks can be utilized at the same time.--[Robert] The VSM doesn't participate in STP so it will never send BPDU's. However, since VMs can act like bridges & routers these days, we advise to add two commands to your upstream VEM uplinks - PortFast and BPDUFilter. PortFast so the interface is FWD faster (since there's no STP on the VSM anyway) and BPDUFilter to ignore any received BPDU's from VMs. I prefer to ignore them then using BPDU Gaurd - which will shutdown the interface if BPDU's are received.-Are you thinking of the upstream switch here (Nexus, Catalyst) or the N1kV uplink profile config?[Robert] The two STP commands would be used only when the VEM (ESX host) is directly connected to an upstream switch. For UCS these two commands to NOT apply. -
Hi all, I know i have mentioned this in the other forum, but i need a bit more clarity.
If I say have a pc plugged into vlan 2, pvid of 2, i gather this means that if ant frame comes in untagged it gets put into vlan 2 right ? ok, well my confusion is what happens to this when it goes over a trunk port, it I put the trunk as member of vlan 1,2,3,etc, will my originally untagged frame that came in and got put into vlan 2 get tagged along the trunk as vlan 2 ?Hi Carl,
I hope i understand ur question correctly :)
you are asking once farme is tagged with vlan id, what will happen to a frame as it pass through a inter switch trunk port.
then the asnwer is (using 802.1q trunking protocol)-
802.1Q does not actually encapsulate the original frame, it sets the EtherType value in the Ethernet header to Tag Protocol ID (TPID) 0x8100, identifying this frame as an 802.1Q frame. It then inserts an extra two-bytes of Tag Control Information (TCI) after the TPID, followed by another two bytes containing the frame's original EtherType. Together the four bytes of TPID and TCI are called the VLAN Tag.
The format of the TCI is
15:13 12 11:0
user_priority CFI VID
user_priority: a 3-bit field is defined in IEEE 802.1p.
Canonical format indicator (CFI): a 1-bit indicator used for compatibility between Ethernet and Token Ring networks.
VLAN ID (VID): a 12-bit field specifying the VLAN to which the frame belongs. A value of 0 means that the frame doesn't belong to any VLAN; in this case the 802.1Q tag specifies only a priority and is referred to as a priority tag. A value of hex FFF is reserved for implementation use. All other values may be used as VLAN identifiers, allowing up to 4094 VLANs. On bridges, VLAN 1 is often reserved for management.
so ur original vlan tag is retained and other end of trunk port will be able to original vlan id of frame.
HTH
rgds
rajat -
The old native vlan question....
Topic came up during troubleshooting a 3524XL sw.
I think my understanding of the native vlan concept is wrong.
I thought on a trunk port (Cisco device) that any packet transversing a trunk link (dot1q trunk that is) has a vlan tag applied on the egress port. As an untagged packet arrives on the port (prior to being sent out over the trunk), its is tagged with the native vlan (if its not assocated with any other vlan), then sent out the (egress) the trunked port.
But lately I have been reading that
"A native vlan is the untagged vlan on an 802.1q trunked switchport. The native vlan and management vlan could be the same, but it is better security practice that they aren't. Basically if a switch receives untagged frames on a trunkport, they are assumed to be part of the vlan that are designated on the switchport as the native vlan. Frames egressing a switchport on the native vlan are not tagged. This is the definition however more recent switch software often will allow you to tag all of the frames, even those in the native vlan. This gives some added security and allows the CoS bits to be carried between switches even on the native vlan. Let me know if you need further clarification."
From : https://learningnetwork.cisco.com/thread/8721
So this tells me that you can have a packet transversing a dot1q link w/o a vlan tag...then when it arrives on the other end its put in the vlan that is on that native vlan question. Is this correct?
If so, and a packet can transverse a trunk link w/o a VLAN tag applied, how does a sw detect (ingress) a native vlan mismatch?
Thanks!Hi,
It's correct, the native vlan is not tagged by default on the trunk link but some platform can make you tag all traffic though even the native vlan.
The native vlan mismatch is detected through cdp.
Regards.
Alain.
Don't forget to rate helpful posts. -
All,
I have a problem that I just cannot wrap my mind around. We have UCS setup in a lab with 2 interconnects connected to 2 nexus 5510 switches. The nexus switches are uplinked to the network via a 4900m switch. All trunks are setup and tested as functional. All routing is setup and confirmed. I have an issue in UCS that is baffling me. In the lab I have kept the native VLAN at vlan1. I have setup test vlans 2-10 on all the switches and interconnects. I have created a service profile that contains 1 nic and placed it in VLAN 7. I have installed Windows 2008 on a blade using this service profile. In the OS I have statically IP'ed the NIC for the scheme used in VLAN 7. From the OS I cannot ping another device that is in vlan 7. I also cannot ping a host on another vlan. If I place a check on VLAN 1 as the native vlan I still cannot ping anything. If I place the check for native vlan to vlan 7 I can ping hosts within the same vlan as well as outside the vlan. So, why do I need to place vlan 7 as the native vlan when all my trunks are set up as vlan 1 being the native vlan?
Thanks for any help,
KenKen,
When allowing certain VLANs on your Service Profile vNICs you need to set the native VLAN. This is because the way you have it configured currently you're only "allowing VLAN 15", but you're not tagging it. This would work fine for ESX or Linux where you can assign the dot1q tag at the host. With Windows unless you have specific drivers doing the tagging for you, you'll need to do this at the vNIC level within UCS.
Two ways to see this in action. When creating a service profile in the "Basic" method - not "Expert", you will select a single VLAN for your interfaces. This will treat the interfaces pretty much like an "Access Port". Conversely when you use the "Expert mode you're enable the vNIC as a trunk, in which you will "allow" all the VLANs you'd like access to. Sounds like this is the method you have performed.
For a Windows OS, set the VLAN as Native for the VLAN you want it to access and you'll be sweet. Unchecking that "Native VLAN" option box is allowing the traffic to traverse out of UCS on the Native VLAN of your network - VLAN 1, which is why it's MAC appears on the other fabric under VLAN1
Regards,
Robert -
I asked this in another forum, but was hoping for some other explanations...
switchport mode trunk
switchport native vlan 80
switchport trunk allowed vlan 50, 80
Can someone provide a line by line explanation of whats being done?
If I understand correctly, the first line lets ALL vlans through this port. The second line lets all untagged traffic that comes from VLAN 80 through. Line three perplexes me, because if we are trunking the port (letting all VLANs through) why explicitly let these two VLANs through when they are already allowed.
Thank you.Hi
"switchport mode trunk" means configure the link as a trunk link ie. a link that can carry traffic for multiple vlans. By default it will allow all vlans.
"switchport native vlan 80" means the vlan on the trunnk link that will not be tagged will be vlan 80. So all other vlan traffic is tagged but not this vlan.
"switchport trunk allowed vlan 50, 80" means only allow vlan 50 and vlan 80 traffic across this link. There a number of reasons you may want to do this. Perhaps at the other end of the link you know that the switch only has ports in vlan 50 and vlan 80 so there is no need to forward traffic for any other vlan. By not allowing those vlans across the trunk you not only stop broadcast traffic from going across the trunk (which can be achieved with the "vtp pruning" command) but you also stop STP for any other vlans than 50 & 80 across the link.
HTH
Jon -
VLAN tagging and tagging question
Hello,
I have a question about VLAN tagging on a Cisco switch.
I've learned that switches tag frames with VLAN IDs once the frame enters a Trunk port (not when it enters a VLAN port).
Now, if two computers from the same VALN and on the SAME switch talk to each other then logically there should not be any VLAN assignment on the frames (as if they were connected to a hub).
Is that correct please?
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Just to muddy the waters, since VLAN edge/access ports don't normally tag frames with VLAN IDs, referencing your question about two computers "talking" to each other, it doesn't matter whether the two ports or on the same switch or even different switches; or in the same VLAN or not.
Also understand trunk ports normally tag frames, and edge/access ports don't, but an exception for the former is the "native" VLAN frames aren't tagged, and an exception for the latter, a Voice VLAN will tag frames.
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