A VLAN that complies with the 802.1Q standard, including priority settings, and allows a port to join multiple VLANs. To handle this, tagged ports have a special VLAN configured on them called the untagged VLAN. Switches can to pass VLAN traffic between each other, so hosts on a VLAN do not have to be on the same switch. This means that you can have one VLAN per port and there is no need to tag the port. When speaking about VLAN ports in HP world, the ports can be tagged or untagged (despite the access / trunk ports in Cisco). So what happens if an untagged packet crosses this link? This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy. If Switch-B were to send the frame, switch-A would tag it as VLAN 15. Hosts in one VLAN cannot communicate with hosts in another VLAN without extra services. CDP is a Cisco protocol used to share information about connected devices. An example of switch-to-switch communication is CDP. For your setup, you would define port 1, on the switch, as a trunk, and by default, both VLANs 10 and 20 frames will be tagged. The VLAN tag contains a Tag protocol identifier, and Tag control information, which can be further broken down into other bit fields such as a VLAN identifier. This means 2 things: The switch will assign the id for it’s native VLAN to any untagged frames entering that port. The traffic generated in this untagged configuration will be free of any VLAN … To create a trunk port you need to set that port to tagged. I am aware of how VLANs work, and how trunks, etc, and even how 802.1q adds and strips VLAN tags. It has to tell the switch which VLANs need to be available on the port. sw1 -> trunk -> sw2. So far data VLANs have been covered, but there are also voice VLANs. Viewed 254 times 0. To connect these two VLANs, there are two cables required. 2. untagged - means that if there is packets on this port that have no vlan id set will have their vlan id tag set to this vlan by the switch. Active 1 year, 8 months ago. Incoming frames will be added to the VLAN on the access port, whatever it may be. When traffic sends to the switch from Host A. Incoming untagged frames are classified into the VLAN whose VID is the currently configured PVID. IPv4, for example, relies upon broadcasts. When the frame enters into switch 1, it will add the VLAN tag ad pass to port 2. Fill in 10 and select the icon to add the VLAN. 3. The standard for this is based on 802.1Q.The standard states that on any given port you can have one untagged VLAN. I apologize in advance if this question is too simple for the group, I just haven't had experience with this topic and am having trouble finding this exact situation with my Google-fu. Hier doe ik iets verkeerds in, tagged, untagged, ik heb van alles geprobeerd. Deze heb ik 'blank' gemaakt op VLAN 1. It is used for broadcast when it sends data from one host and it will pass to all the hosts connected in the port. 6. Firstly, the frame would be tagged as VLAN 15 when entering Switch-A. Port 7-9 are members of all 3 VLANs: 101, 102 and 103. (The switch sets either tagged or untagged egress.) We can select each port a one VLAN which outgoings packets are untagged. Host A sends traffic to the switch. If an untagged packet enters a port, it is automatically tagged with the port’s default VLAN ID. VLAN 10 is voor het LAN van de tweede router en staat tagged op alle trunks en untagged op de poorten waar zakelijke apparatuur op aangesloten is. Tagged vs. Untagged : Een trunk zal dus altijd zijn verkeer tagged afleveren en ontvangen om de pakketjes in het juiste vLAN terecht te laten komen. It is recommended to limit the VLANs that are allowed over a trunk link to only the VLANs that are needed. Managed switches allow for traffic separation by using VLANs. VLANs > New VLAN ID. 4. Switch 2 determines that port 2 should send the frame, Since port 2 is an untagged port, it strips the tag from the frame, and then sends it, Switch 1 receives the frame on the trunk port. This can be done using the following commands: Conf terminal. Untagged means it will strip the tag. If a frame on the native VLAN leaves a trunk (tagged) port, the switch strips the VLAN tag out. Jaspreet Singh 2018-03-22 15:41 © 2020 - EDUCBA. As you may guess, tagging means 802.1q tagging in Ethernet frames. Is this correct? Ports on a switch can either be untagged (does not tag packets; belongs to a single VLAN) or tagged (tags packets; can carry multiple VLANs) When an untagged port receives an untagged packet, the switch will forward the packet based on the VLAN configured on that port; When an untagged port receives a tagged packet, the switch will drop the packet if the tag on the packet is not the same as the VLAN … Add port 4 to the VLAN as tagged port. Below are the top 7 differences between VLAN Tagged vs Untagged: Let us look at the key differences between VLAN Tagged vs Untagged: When the frames contain the VLAN tags, it is the tagged port. In this case, the switch will flood the frame to all other ports configured with VLAN 10. THE CERTIFICATION NAMES ARE THE TRADEMARKS OF THEIR RESPECTIVE OWNERS. Separating these out will prevent this from happening (at layer 2). Why do people sometimes say that it can’t? CT (unverified) 2018-06-08 04:46 The sender will send a frame with a VLAN tag. Fundamentally i guess the above is the source of my confusion as my understanding is/was that in networking the 'Native vlan' does not equal 'untagged', but instead it means 'tagged with whatever the native vlan is on that switch' which is, as you said, typically vlan 1.... 0 Kudos Under port 7 and port 8, change VLAN10 and VLAN20 from Excluded (E) to Tagged (T). When we built a larger network, we need more router to manage the workload. A port can be an untagged member of only one port-based VLAN. For the untagged packet, we can also force the port to access it. Also, there are also some types of layer-2 traffic that will always use VLAN (at least on a Cisco switch), such as CDP and LLDP. Add port 1 and port 2 to the VLAN as untagged ports. The connected host sends the traffic on any VLAN and it will reach the port, the switch will add the VLAN tag. VLAN Tagging Vs VLAN Untagging-Difference between VLAN Tagging and VLAN Untagging. No untagged– The port is not a member of that VLAN. The untagged VLANs are connected to the host or the servers. Resources to expand your networking horizons, Last Updated: Jan 6, 2020 @ 9:35 am (UTC). In general, use trunking to connect switches. In the old days before switches and VLANs existed, Ethernet networks connected via hubs. Or does this not make any difference? The switch will add a tag to all. Basic switches, called ‘unmanaged switches’ have only simple functionality. If VLAN 10 not allowed, then the frame will drop. If you set a VLAN to be untagged on a port, there is no PVID associated with it; there is no PVID field in the Ethernet frame. The solution is to change the default VLAN to another value. These are generally misleading concepts. Each port on the switch is designated as Tagged, Untagged or Excluded in each VLAN. When CoS is used, and a client does not know what VLAN to use, it can tag a fram with VLAN 0, which causes the switch to use the native VLAN for that traffic. You can add additional VLANs as "tagged". This includes reserving VLANs for management, or creating ‘remote VLANs’ for use in ERSPAN ports. Yes, it can definitely be done. The standard for this is based on 802.1Q.The standard states that on any given port you can have one untagged VLAN. This is very similar to the Native VLAN Mismatch scenario above. The untagged VLAN is enabled to send traffic without the VLAN tag. Kurz und Knapp: untagged. Note2: Any untagged traffic can always enter any port, it will be internally assigned to the port's PVID. 802.1Q VLAN Tagged Vs Untagged. vlan 1 untagged and vlan 2 tagged. In the untagged port, when frame leaves, the switch will strip VLAN tag from the frame. It’s great to hear that this has been useful to you! VLAN enabled ports are generally categorized in one of two ways, tagged or untagged. The standard for this is based on 802.1Q.The standard states that on any given port you can have one untagged VLAN. Each of these VLANs may be configured to be tagged or untagged. Apply the changes. Inversely, does "Untagged" strip it off as it leaves the port to the wire, or is it stripping it as it goes into the switch. Ask Question Asked 1 year, 8 months ago. If the port was UNtagged, then it will still send the frame, but the switch removes the VLAN header first. Tagged ports should be connected to switches or devices with multiple VLANs. At least a host failure does not cause a break in the chain. you have 5 vlans as you say eg. You explained this better than many other resources I have used and have helped me to understand. An only switch port can be configured in Access port. There are two types of frames that could pass through this link; tagged and untagged. Cisco switches use the term ‘trunk’ to refer to a tagged port. Consider this Example. Untagged– When a port is untagged, it can only be a member on one VLAN. they are tagged by the network device connected to … As shown below, the tag is right after the source MAC. The switch assigns any untagged frame that arrives on a tagged port to the native VLAN. Finally, the FCS is recalcualted based on the entire frame. How To Create & Assign Vlan Tagging On Switch It consists of: The frame has a four-byte VLAN tag added, which includes the VLAN ID. The host is unaware of any VLAN configuration. 3. Under port 7 and port 8, change the default VLAN1 from Untagged (U) to Excluded (E). This is sometimes done for management traffic. Then, as before, when it enters switch-B, the untagged frame will have a VLAN 20 tag applied. More than one VLAN can be configured in trunk port. Tagged means the port will append/preserve the VLAN tag on outgoing packets. Additionally there are methods of manipulating VLANs for security, such as private VLANs. An example service is a router to pass packets between the VLANs. So, that being said, the “native VLAN” is the VLAN associated with all untagged traffic on a trunk (and can be set on a per-port basis). The traffic is then forwarded as normal. Ik heb de volgende website 10 maal doorgelezen, maar tagged en untagged blijft onduidelijk. Ask Question Asked 1 year, 8 months ago. Untagged: Allows VLAN connection to a device that is configured for an untagged VLAN instead of a tagged VLAN. Traffic that goes through this VLAN will not be tagged with a VLAN ID. This is called VLAN pruning, and can be done manually, or dynamically with DTP. My question: If I set a port up to be "Tagged", is it putting the tag ON as it leaves the port to the wire, or as it goes in. Trunk mode is for tagged VLANs and you are correct you would take a port with all of the VLANs you need. While others claim that a tag is added on a trunk port, even the vdu on your YouTube channel says so. Therefore, the only concern here is for untagged traffic. VLAN 10 port 1-12 untagged port 13-23 tagged port 24 exclude all VLAN 20 port 1-12 tagged port 13-23 untagged port 24 exclude all Trunk port 24 This is knowledge, experience and what i got from my friends about configuration in HP Procurve v1810-24g, likely the concept of this VLAN is similar with Switch of Dell and others. The purpose of a tagged or "trunked" port is to pass traffic for multiple VLAN's, whereas an untagged or "access" port accepts traffic for only a single VLAN. However, the native VLANs (15 and 20) do not match, resulting the error above. Omdat bij mij de televisie dus gewoon over VLAN 1 loopt heb ik IGMP snooping aan staan op VLAN 1. In the 802.1Q VLAN Setting section, enter 2 in the VLAN (1-4094) field. Step 2: Choose the menu VLAN > 802.1Q VLAN PVID Setting to load the following page. The switch only sends untagged traffic on the native vlan. Under port 7 and port 8, change the default VLAN1 from Untagged (U) to Excluded (E). By closing this banner, scrolling this page, clicking a link or continuing to browse otherwise, you agree to our Privacy Policy, New Year Offer - All in One Software Development Bundle (600+ Courses, 50+ projects) Learn More, 600+ Online Courses | 3000+ Hours | Verifiable Certificates | Lifetime Access, Java Training (40 Courses, 29 Projects, 4 Quizzes), Python Training Program (36 Courses, 13+ Projects), HTML Training (12 Courses, 19+ Projects, 4 Quizzes), Difference Between Method Overloading and Method Overriding, Software Development Course - All in One Bundle. If traffic should go from switch to switch, then I would think that the port should be vlan 1 tagged and vlan 2 tagged. The switch assigns any untagged frame that arrives on a tagged port to the native VLAN. This should be the same VLAN that is marked as untagged on the access port. – VLAN untagged vs tagged. Have a look at this diagram for an example: In this example, the two switches are connected with a trunk link. General is for ports that might have multiple devices and one needs no vlan tag, such as ip phone and pc. This is an Untagged port. So if switch-A were to send a frame to switch-B, it would be sent untagged, and switch-B would tag it as VLAN 20. VLAN 0 is reserved for special use. ALL RIGHTS RESERVED. The frame contains the tag of the destination address, so a single port can be established to accomplish the connection between the two switches. 4. This is a tagged port, so it checks that VLAN 10 is allowed on this port. The default setting is 1. As discussed earlier, when an untagged frame enters a switch port, the native VLAN is tagged on the frame. You can have tag ports. This article is very unique to a VLAN beginner like me. To accept untagged packets the native-vlan-id and flexible-vlan-tagging statements must be included at the [edit interfaces interface-name] hierarchy level: VLANs > New VLAN ID. Only the config relevant to the type will be used. With Cisco devices, an untagged switch port will connect to hosts that have no idea of any VLAN configurations within the networking environment. Add port 2 to VLAN 1 and VLAN 2 as untagged port; add port 3 to VLAN 1 and VLAN 3 as untagged port; Add port 4 to VLAN 1, VLAN 2 and VLAN 3 as tagged port. Untagged poorten zijn in de meeste gevallen bedoeld voor de endpoints zoals computers, laptops, printers etc. You can have many vlan data packets via a switch port with is set as tagged. I read the article word by word, many times. The difference is that although traffic will flow, essentially only one VLAN is being allowed from one switch to the other. Bericht door Robert Ford » 21 Mar 2014, 15:39 . The short answer is; no. Enter the VLAN ID (between 1 and 4094) for the untagged VLAN in the Untagged VLAN ID field. An example of this is when two switches are connected, and pass tagged traffic. Port 4 does not have a PVID of 102. Here, you can see this process in action: In some cases, an untagged frame will arrive on a tagged port. A Trunk can have exactly ONE untagged vlan (also called the Native VLAN), and one or more Tagged VLANS. It may also be used to extend the number of available VLANs. Tagged packets are only understood by network equipment that is VLAN aware. Under port 7 and port 8, change VLAN10 and VLAN20 from Excluded (E) to Tagged (T). To accept untagged packets the native-vlan-id and flexible-vlan-tagging statements must be included at the [edit interfaces interface-name] hierarchy level: tagged (802.1q) tagged bedeutet, dass sich das Gerät mit dem VLAN tag melden muss um in dem VLAN zu landen. Fill in 10 and select the icon to add the VLAN. Sometimes you may hear of VLAN 1 being a special or reserved VLAN on Cisco switches. Assigning a host to a VLAN allows it to communicate with another host on the same VLAN. Here is the definitions for each network switch Vlan setting: Tagged: Allows the port to join multiple VLANs. Tagged VLANs (as opposed to Untagged) on a port are typically used when connecting to a host that needs access to several networks at once using the same interface, such as a server providing services to more than one department in an office. It is much secured, so we need to manage virus/malware-free. HP Switch tagged vs untagged VLAN poort. VLAN 4095 is used internally within a switch. It is special as it is the default. Tagged vs. Untagged VLANs. This is a method of subdividing VLANs to segregate traffic within a VLAN. If VLAN 10 is not allowed, it drops the frame, Switch 2 receives the frame on tagged port 1. De PVID van die poorten van de switch is dan ook 10. If I'm setting up multiple VLANs, I'm wondering what the difference is between the VLAN Membership settings (where you click on the ports, per VLAN, and assign either tagged, untagged, or no traffic to).. and the PVID value you assign to each port on another screen (can't remember the screen right now, it's not in front of me). These may also be referred to as "trunk" or "access" respectively. If it is the tagged port, it will check the port if it allows the VLAN 10 to leave the tag intact and sends the frame. untagged bedeutet, dass der komplette switchport dem VLAN angehört. This setting applies to transmitted frames. Most switch ports will use this mode by default, with VLAN ID 1. A PVID is the Port VLAN ID, which is essentially just the default VLAN ID that is configured for all untagged frames on that port The main thing to think about with tagged versus untagged ports, and VLANs in general, is that for the setup to work there will be subnetting involved. 7. When the frame reaches the switch port, the switch will add the VLAN tag. Know the difference between a LAG and a trunk? I work for a consultancy where we usually send a small team to work at the customer's site. Each port on the switch is designated as Tagged, Untagged or Excluded in each VLAN. Another reason to separate hosts would be for security. This means that the VLAN config on one switch does not have to exactly match the switch it is connected to. Untagged port membership, between two VLAN-aware devices with no intervening VLAN- aware devices, should be to the same VLAN. Generally an untagged trunk would be useless, as its the tags that allow the VLANs to be kept logically separate on a trunk. One main limitation to hubs were that all hosts were on the same collision domain. A VLAN that does not use or forward 802.1Q VLAN tagging, including priority settings. Consider two examples. The following diagram shows this process: A port is a ‘tagged port’ when the interface is expecting frames containing VLAN tags. This helps to limit the propagation of broadcasts, and is good for security. You may also have a look at the following articles to learn more –, All in One Software Development Bundle (600+ Courses, 50+ projects). Now I telling about the feature, advantage and used of Vlan. Hey SushilI will do my best. Within the network, physical ports are configured as untagged or tagged for a specific VLAN—determining whether to accept and forward traffic belonging to each VLAN ID. They have no configurable VLAN support. Once a port is made hybrid, you can tag the interface in one VLAN and untag the same interface in another VLAN. Each port has a default VLAN ID that is you can configure. The default setting is 1. The default ID is 1. Hey SushilI will do my best. Each of these VLANs may be configured to be tagged or untagged. Then when the frame is received in port 1, the switch inserts the VLANs tag into the frame. This has been a guide to VLAN Tagged vs Untagged. Any traffic sent over the trunk link for any of those vlans will be tagged with the relevant vlan ID. This is also known as the ‘native VLAN’. Then, you must decide whether each port will be a tagged member or an untagged member of the VLAN. If a port is Tagged, the switch will add the VLAN ID to the header of any packets sent on that interface. Thanks, Otherwise, traffic will leak from one VLAN to another. Here we discuss the VLAN Tagged vs Untagged key differences with infographics and comparison table. I will assume those VLANs are tagged … This is CDP informing you that the current configuration is not best-practice, and may result in some unexpected behaviour. Be aware that there are other VLAN types and uses, which fall outside the scope of this article. If the packet is tagged, we can’t do much about it, and the rest other will be rejected. Tagged vs. Untagged : Een trunk zal dus altijd zijn verkeer tagged afleveren en ontvangen om de pakketjes in het juiste vLAN terecht te laten komen. The ports that the hosts connect to are trunk ports, with native VLAN 15 configured. It will send the data based on the VLAN ID. A port can only have one Untagged VLAN configured at a time. 4. 5. A frame leaving an access port will not be tagged. The primary function of a VLAN is to separate layer 2 traffic. Any tagged traffic will be passed without being changed, due to this being a trunk link. I assume it is not included in the snipped. 802.1Q VLAN Tagged Vs Untagged. “Switches can to pass VLAN…..”. When a frame leaves an untagged port, the switch strips the VLAN tag from the frame. 3. This setting applies to transmitted frames. The untagged VLAN is enabled to send traffic without the VLAN tag. Specify the VLAN name as Group_A. This means that for example, if the 5548 send untagged packets from VLAN 2,3,4 across the Trunk connection to the 6248. Luke Robertson 2018-06-09 18:40 Carrying untagged traffic has its uses. This switch also determines if VLAN 10 is allowed on this port, and drops it if it is not. Tagged Interface vlan 2. However, Cisco trunks also generally allow one VLAN to be untagged (by default, VLAN 1). Specify the VLAN name as Group_B. Thanks, I appreciate the comment cool. VLAN-tagged frames can pass through VLAN-aware or VLAN-unaware network interconnection devices. The switch then inserts the VLAN tag into the frame, The switch determines that the frame needs to be forwarded out of port 2. VLAN Tagged e Untagged em Switchs 3COM/HP VLAN - Trunk utilizando 802.1q (dot1q) A utilização de VLAN (Virtual Local Area Network) permite que uma rede física seja dividida em várias redes lógicas dentro de um Switch. On port 24, both VLAN10 and VLAN20 is carried out over that port. VLAN config is all locally significant. Alleen heb ik schrik dat ik hier en daar tagged/untagged heb fout staan en dat het daarmee niet werkt. The FCS is also removed during this stage. All other port in that Vlan are untagged. This is sometimes used by service providers to keep customer traffic separate. If an untagged packet enters a port, it is automatically tagged with the port’s default VLAN ID. It looks contradictory to me to say that the packets are sent on 'vlan1' and 'untagged' as I understand vlan1 to be a tag as all the others are, with the exception that vlan 1 is typically the native vlan that all switch ports use and so by default are tagged with that ID. This was a bit like chaining each host to the next one. The process of configuring port as tagged means placing or inserting 802.1q compliant tag in the ethernet frame. So, to make a translation from HP/Aruba to Cisco: untagged = access port tagged = trunk port. Thanks CT Although, keep in mind that each switch, in this case, would see a different VLAN, such as VLAN 15 and 20 in the previous example. Being different from most (if not all) VLAN training materials, this article states that a tag is added on an access port when a frame comes in from a host. From Ubiquiti website This VLAN ID tag may be added or removed by a host, a router, or a switch. In a multitenant data centre, it is important that one customer’s data is not visible to another. tagged untagged forbid. Ik gebruik een NETGEAR GS724Tv4. Each VLAN is identified by an ID which is a number. If you need to pass frames tagged VLAN 1, you will not be able to, by default. The connected host sends its traffic without any VLAN tag on the frames. Unfortunately, this gets cost prohibitive, which is why VLANs are often preferred. Untagged poorten zijn in de meeste gevallen bedoeld voor de endpoints zoals computers, laptops, printers etc. Note: If you did not enable an untagged VLAN, skip to Step 4. It’s my VLAN bible. Untagged VLANs. As VLAN 1 is the default native VLAN, it is used for untagged traffic. If that frame is then forwarded over a trunk port, it will have a tag added. This happens when one switch wants to send information to another switch. So, if traffic will still flow between the switches, even if there is a native VLAN mismatch, what’s the syslog error all about? Here all the PCs are connected in one switch and can be communicated with each other. The host will send the frame without a tag. However, the interesting part is that the VLAN 15 tag will be stripped when it leaves switch-A, as it matches the ‘untagged’ native VLAN on the uplink. Step 3. Hubs placed all networked hosts onto a single ethernet segment. Tagged: Assigning a tagged VLAN to a port adds that port to the VLAN, but all ingress and egress traffic must be tagged with the VLAN ID in order to be forwarded. It is important to realize that Cisco is “port-centric”, whereas Procurve is is “vlan-centric” when speaking about vlan … The purpose of a tagged or "trunked" port is to pass traffic for multiple VLAN's, whereas an untagged or "access" port accepts traffic for only a single VLAN. This means that the client is responsible for the tagging. Forbid– The port is “forbidden” to join that VLAN. Once this is done, VLAN 1 can be passed across the trunk just the same as any other VLAN. To see how to design with VLANs in mind, check out the Hierarchy Design articles, Your Networking World – IEEE 802.1Q Frame Format, Packetlife – VLANs are Locally Significant. It uses the word ‘Trunk’ to refer to the tagged port. It’s also possible to use double-tagging, which is adding two tags to a frame. This is an untagged port, configured with VLAN ID 10. Server-to-server communication could use a ‘secured’ VLAN. The receiving switch will see the VLAN tag, and if the VLAN is allowed, it will forward the frame as required. For your setup, you would define port 1, on the switch, as a trunk, and by default, both VLANs 10 and 20 frames will be tagged. So in principle, you can only say a port is a tagged or an untagged member of a VLAN, but not that the port itself is tagged or untagged. The VLAN ID is 12-bits long, which allows for a theoretical maximum of 4096 possible VLANs. The switch port is configured with a VLAN ID that it will put into the tag. Without VLAN technology a big network can’t be handled. A frame entering an access port will become part of a VLAN. It will send the data based on the VLAN ID. Tag port mean the packets have already a VLAN-tag, i.e. This means that for example, if the 5548 send untagged packets from VLAN 2,3,4 across the Trunk connection to the 6248. This was still an improvement on older token-bus networks. Apply the changes. I may have phrased it badly. The VLAN is like a virtual switch in concept. Below is a normal ethernet frame. Because when one system affects, it will extend to the entire network. If a port is Tagged, the switch will add the VLAN ID to the header of any packets sent on that interface. Your hypothetical packet tagged VLAN 10 ingressing on port 1 would have its tag stripped and when it egressed port 2 (or port 3, because both are untagged members of VLAN 10). Of course, one way of achieving these goals would be to connect each group of hosts to their own switch. To handle this, tagged ports have a special VLAN configured on them called the untagged VLAN. This means that all hosts on the switch are still part of the same broadcast domain. Viewed 254 times 0. The switch adds the VLAN tag to the frame, Switch 1 determines that port 2 should send this frame to switch 2. On vSRX tagged and untagged sub-interfaces can be configured on the same physical interface. If you remove VLAN1 or configure VLAN1 as "tagged" you have no native VLAN. THANK YOU!! What would happen if a host on Switch-A were on VLAN 15, and it sent a frame to a host on Switch-B? VLAN 10 port 1-12 untagged port 13-23 tagged port 24 exclude all VLAN 20 port 1-12 tagged port 13-23 untagged port 24 exclude all Trunk port 24 This is knowledge, experience and what i got from my friends about configuration in HP Procurve v1810-24g, likely the concept of this VLAN is similar with Switch of Dell and others. This means that if two hosts transmitted at once, the data could ‘collide’, and have to be resent.