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Can someone please explain the difference between access ports and trunk ports on a switch? I'm starting to learn networking, and my understanding is that access ports are used to connect endpoints (e.g. computers and printers) to the switch and trunk ports are used to connect two switches together. Any help will be greatly appreciated. Thanks!

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3 Answers

up vote 10 down vote accepted

An access port sends and receives untagged frames (i.e. all frames are in the same VLAN), while a trunk port supports tagged frames and thus allows to switch multiple VLANs.

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And therefore, trunks can be used to connect endpoints that support VLAN tagging. And access points can be used to connect a single VLAN to dumb switches that don't. –  David Schwartz May 4 '12 at 8:04
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For what it's worth, in my experience, both other answers (Oliver's and Ignacio V-A's) are correct, despite being different.

(Edit: I notice that Ignacio has since deleted his answer; the upshot of his answer was that trunk ports were higher-bandwidth-lower-latency ports on a switch, possibly better connected to the backplane, into which I read the suggestion that they were for inter-switch communication. I add this note only because, without it, my answer will make no sense to people without the rep. to see deleted answers.)

My old-time experience is that trunk ports are what Oliver says, that is, ports which will accept 802.1q VLAN-tagged packets, and switch them accordingly.

However, at least one switch I've used recently (the HP Pro Curve 1810G) uses "trunk port" to mean "a port which will be combined with one or more other ports for the purpose of a multiple-parallel-cable high-bandwidth link, usually to another switch"), as IVA does. Where trunk is used in this sense, the chassis may have dedicated trunk ports for inter-switch connection, and in at least some cases, these may have a preferential path through the backplane.

And yes, this overloading of the term "trunk" meant that it took me a whole day to set up an eight-port switch, when I was expecting the VLAN setup to take about 90 minutes. Why do you ask?

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We're just talking terminology here. I think Cisco are the only ones who call a port that will carry multiple vlans, ie tagged frames a "Trunk". Most everybody else will call them "Tagged Ports". The original question is already answered previously. –  user178183 Jun 18 '13 at 1:56
    
@NZalias Cisco is not "the only" company that uses this terminology, it's pretty common. Likely because Cisco is the dominant network device supplier. –  voretaq7 Jun 18 '13 at 3:25
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Trunk port is used to connect between switches and access port is used to connect to computers lap top printers etc, you cannnot extend the data from one switch to other switch access ports through trunk port. it can only extended through access port of switch.

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-1 That makes very little sense, and what I can understand seems wrong. Sorry, but especially when posting to year-old Questions, we're looking for well thought out, complete, and accurate Answers. –  Chris S Mar 20 '13 at 14:02
    
Your understanding is generally correct, but your reasoning is wrong. "Trunk Ports" (carrying multiple VLANs, with tagged traffic) are usually found used as inter-switch links, and "access ports" (usually carrying only one VLAN, untagged) are usually found going to end workstations, but this is by no means exclusive: You may have "trunk ports" (or "tagged ports") to end user desks, with a voice VLAN (usually tagged - for a VoIP phone) and a data VLAN (untagged, or "native" - for their workstation). –  voretaq7 Jun 18 '13 at 3:29
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