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Switches / Hubs





A switch is a device that filters and forwards packets of data between LAN segments. Switches operate at the data link layer or the network layer of the Open Systems Interconnection (OSI) Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. A hub is a connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports; when a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

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I have a few electronic devices in a room which do not need to be on when there is nobody in the room.

The times are variable for when people would be in the room.

These devices are plugged into an extension lead which I would like plugged into a sensor socket.

Ideally what I would like is for when someone walks in the room, the sensor socket would switch on and the devices would in turn switch on too.

The opposite would happen when someone leaves the room for a few minutes.

I would like one that does not require a hub or Wi-Fi as I would have a switch connected to this sensor socket.

Also, it would be an advantage if the sensor socket did not turn off if people were sitting down watching TV but not making much movement.

What would you recommend?

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I have a virtual machine running Server 2012. The host machine machine is running Hyper-V. I need the virtual machine to be on a separate VLAN with only internet access and possibly some limited access from other machines on the local network. The host machine connects to a Cisco 3560X managed switch. The switch is connected to a port on our Sonicwall firewall.

I am not sure what the best approach is nor would I know exactly how to configure it.

I think the main concern I have right now is how to configure the port on the Cisco switch. Will adding the VLAN during work hours cause any distrubtion?...Do I need to make any changes on the firewall?
Hello there.  I am wondering If I can use old IBM QLE2460 cards, fiber channel with a switch, like brocade 300 to emulate ethernet connections of 4GB.
In the same manner, I am wondering If I can HP 10GB MELLANOX CONNECTX-2 cards ( windows 2012R2 of windows 10) with a switch like  Mellanox MIS5025Q-1SFC to emulate 10GB connection. Also, it would be fantastic if there was ESXi 6.x support for this. Please advise!!!!  Are there any limitations that I would be aware???

Ps. When I say emulate I mean to use Fibre or Infinity band to work as ethernet with proper drivers and switch configuration.
At the physical layer what needs to be detected?

We're trying to plug in a phone into a switch that is primarily used for data but was configured for data and phone, however, when the phone is plugged in it does connect to the network. Below is config from the data switch configured for data and phone and a switch configured for only phones ( or at least that what we use it for).  Please let me know. Thank You.

Switch configured for use with phones - both data and phone work

interface FastEthernet2/0/39
 switchport access vlan 10
 switchport voice vlan 20
 srr-queue bandwidth share 10 10 60 20
 srr-queue bandwidth shape  10  0  0  0
 mls qos trust device cisco-phone
 mls qos trust cos
 auto qos voip cisco-phone
 spanning-tree portfast

Switch configured for DATA - Only Data works (what do we have to configure for phones to work?)

interface GigabitEthernet3/0/46
 switchport access vlan 10
 switchport voice vlan 20
 spanning-tree portfast
Sysadmin is complaining that when traffic to his server is a little higher than usual (say 300Mbps on a 1Gbps interface) that he's seeing Rx errors on his interface. If I look at the switch that is connected to his server it shows everything clean. No errors Rx/Tx - just an increase in throughput once a day. It's a linux system. What can I advise him to do regarding errors on higher than average throughput? Anything else I could do on the Cisco switch side?
I have   setup  2 separate Labs ,  VPNV4 and AToM.
I found out that VPNV4 configuration is very complex compared to the configuration of AToM(Any Transport over MPLS) which is very simple.
Now, I am not sure if there is a catch behind this simplicity. I mean is VPNV4 capable of offering more services than AToM.
Thank you


AToM LabAToM Lab:
Hi Guys,

I'm looking after a site that has one or two bandwidth problems.  Topology is as follows:

It has a couple of Cisco 2950 switches and a Cisco 3560 switch which is configured to have a few VLANs.  Due to the geographical location of the site, internet lines are poor.  We have two gateways (30mb an 16mb) on this site and I have configured PBR to give a certain amount of load balance.   The gateways themselves are just the standard Netgear/D-Link type routing devices.

We are finding at certain times the bandwidth is much slower than we would expect and suspect one of the vlans is the culprit.  I'm going to setup SPAN on the port of the gateway the VLAN is using, then sniff and monitor the traffic.  I'm pretty sure what I'll find.  

So my question is.  What is the best way to limit the ingress and egress traffic from a particular VLAN from the 3560 switch.  I'm not bother about traffic type, just want to limit ALL inbound and outbound traffic to a specific rate.

I'm not sure if it's possible or feasible.  Have seen lots of stuff about rate-limit and policing etc, but nothing definitive.  I'm trying to avoid changing the topology too much by perhaps sticking in a Cisco router or swapping out the Gateway boxes for something that can handle more of the Enterprise type options.

What do you think?  I'm I flogging a dead horse, or do I need to change the topology.

Thanks for your help guys
Dear Wizards, can you please suggest on this scenario?

If a physical host (with 4 physical NICs) connect to Core Switch Cisco  3925, can we use the Link Aggregation Control Protocol (LACP) to increase the bandwidth for that host? And if so, how to increase the maximum bandwidth for virtual NIC of VMs inside that host?

Many thanks in advance!
I have 4 switches in this issue, 2 core switches (3650 in stack) and then 2 2960-x each on different floors.  

First 2960 has a link to the core switches, and the second is trunked to first 2960.  I have each of the 2960 with a management IP assigned to vlan1.  Port config is as follows

2960-1   Port 1/0/48 trunked to 3650 stack port 2/0/48

2960 2  port 1/0/48 trunked to 2960 1 port 1/0/47

all ports in trunked mode with switchport trunk vlan allowed all  

I'm not sure if i need dot1q on the 2960's to work.  But i'm not able to access the management ip of either 2960.  Was hoping to have someone peek at the config and see if i'm missing something.  

The 3650 config for that interface :

interface GigabitEthernet2/0/48
 description Link to COB-ITCONF 2960
 switchport mode trunk
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I have an 8 port SG200, and it's constantly hitting my tftp server on my desktop.
How do I get it to stop, unless manually searching for a tftp server?
I'm considering purchasing the SG200-26P switch, as I have about 11 or 12 devices, some use POE.
The problem is, I'm looking for a fanless switch, or something that is very quiet.  I'm currently running a 3750G POE 24P, and it's to loud in my office.

Can the SG200-26P be managed by the CLI as well, as I know it has a GUI, but it would be nice to use the CLI as well?
Is the switch fanless?
Hi, I am having a bit of trouble getting something working, and was hoping for some advise.

For various reasons, I HAVE to use MAC based VLAN, and i have something partly working, but not fully.

My setup is
2 x Netgear GS752 Smart Switches
PC11 : Connected to Switch1 : port1
PC14 : Connected to Switch1 : port4
PC25 : Connected to Switch2 : port5
Switch1-port50 connected to Switch2-port50

Switch 1
Port   : 1 2 3 4 5 6 7 50
VLAN 1 : U U U U U U U T
VLAN20 :       U       T
PVID   : 1 1 1 1 1 1 1 1
PC11 : MAC Based VLAN assigned to VLAN20

Switch 2
Port   : 1 2 3 4 5 6 7 50
VLAN 1 : U U U U U U U T
VLAN20 :         U     T
PVID   : 1 1 1 1 1 1 1 1

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So, PC11 has its MAC address assigned on Switch1, and on both Switch1, and Switch2, the switching address table shows PC11's MAC as being on VLAN20.

PC11 can Ping PC14 without problems
PC11 CAN NOT ping PC25.

I don't understand why PC11 CAN NOT ping PC25 ?

Its really important to understand that PC14, and PC25 must be able to communicate on VLAN1 and/or VLAN20 depending on the clients(PC11) MAC Address

The Reason MAC Based Vlan is a requirement is that on some client machines, you have both the Host operating system, and some Virtualbox OS's which are not permitted the same network access

There are NO VLANID settings on any of the PC's network cards ( as again this would not work in my setup)
Any thoughts or advise greatly appreciated
I have a  topology with 1 x Cisco WS-6509-E Layer 3 Switch connected to 1 x HPE FF 5700-40XG-2QSFP+ Switch and another HPE FF 5700-40XG-2QSFP+ Switch. These HPE FF 5700s are each connected to 2 x HP 5130-48G-PoE+-4SFP+ (370W) EI Switches and 1 x HP 5130-24G-4SFP+ EI Switch. The Cisco WS-6509-E has the udld aggressive command globally configured. I am trying to establish two connections running from each HP 5130 switch to each of the HP FF 5700s. I have the udld aggressive command configured globally on the Cisco WS-6509-E. On two of the HP 5130s I have the lldp compliance cdp command configured but on one I don't have it configured. When I try to make a dual connection from the switch running from the switch with lldp compliance cdp command configured, I get the link to one of the HP FF 5700 placed into err-diabled. The logs below show what happened:

Jul 15 11:08:28.682 PDT: %UDLD-SP-4-UDLD_PORT_DISABLED: UDLD disabled interface <port>, unidirectional link detected
Jul 15 11:08:28.682 PDT: %PM-SP-4-ERR_DISABLE: udld error detected on <port>, putting <port> in err-disable state
Jul 15 11:08:28.758 PDT: %PM-SPSTBY-4-ERR_DISABLE: udld error detected on <port>, putting <port> in err-disable state

Should I undo lldp compliance cdp command on the HP 5130 switches in order to get a dual connection to the HP FF 5700s?
We have an HP Procurve 2920 POE switch. We have been having issues with our new VOIP service so I am becoming very familiar with our switch configuration. One thing I am noticing is that while POE seems to be working to all of our devices, only 3-4 of them show port status "delivering" in the switch. The rest of the devices show "searching". Any ideas?

I need to activate or configure around 14 ports on our project.  One for vlan 10 and one for Vlan20.  What are the things I need to prepare and   What are the commands I need to use .  The switch is  Cisco 3940.

Thanks in advance
I would like to connect to buildings over Cat6. These buildings are 200meters away! I dont now about the earth potential differences. I raed some intrestings about Network isolator(installed as part of a copper Ethernet system, as galvanic isolators). I think thats would work!  
Switch->Poe injector->Poe Extender->Network isolator->Switch

Thanks for yor support
I am attempting to force all ShoreTel IP Phones onto the voice VLAN.  However despite various attempts the connected devices remain on the default VLAN.  Due to computers connected to the pass-through Ethernet ports on the phones we cannot use the primary VLAN for the port.

I have a phone with a computer in pass-through connected to gi6.  I have been attempting to coax the switch to place the phone on VLAN 10.  Yet I consistently receive the following output:
switchb#sh mac add int ge6
Flags: I - Internal usage VLAN
Aging time is 300 sec

    Vlan          Mac Address         Port       Type
------------ --------------------- ---------- ----------
     1         00:10:49:45:8c:26      gi6      dynamic
     1         08:2e:5f:07:b1:7d      gi6      dynamic

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Running Config:
switchb#sh run
v1.4.8.6 / R800_NIK_1_4_202_008
CLI v1.0
set system mode switch

file SSD indicator encrypted
ssd config
ssd file passphrase control unrestricted
no ssd file integrity control
vlan database
vlan 2,10,65,200-201
voice vlan id 10
voice vlan state oui-enabled
voice vlan oui-table add 0001e3 Siemens_AG_phone________
voice vlan oui-table add 00036b Cisco_phone_____________
voice vlan oui-table add 00096e Avaya___________________
voice vlan oui-table add 000fe2 H3C_Aolynk______________
voice vlan oui-table add 001049 ShorTel
voice vlan oui-table add 0060b9 Philips_and_NEC_AG_phone
voice vlan oui-table 

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Further to the question I posted above, besides the 30+ critical PCs (for Swift processing), we have about
20 Tally network printers used to print critical SWIFT messages : the PCs & printers are at various physical
locations : 1-3 PCs may spool print to one of those printers.

Heard that in Banglades bank's SWIFT heist, hacker intercepted print job, learnt how to send fabricated
data to the printer.   We can secure the PCs with Windows Firewall but what about the printers?

To create isolated VLANs & move these PCs & printers to the dedicated VLANs require changing IP addrs
of these PCs/printers & may incur downtime & if not planned carefully, disruptions.  Would creatiing
MAC addr ACLs on the switches that these PCs & printers are connected to help?

Our netwk support said it's no longer a common practice to do MAC-based ACLs? Is this true?
Or it's simply too much of an effort for the 30 PCs & 20 printers?

Can Layer 2 switch support MAC ACLs?
Important Lessons on Recovering from Petya
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Important Lessons on Recovering from Petya

In their most recent webinar, Skyport Systems explores ways to isolate and protect critical databases to keep the core of your company safe from harm.

I have a subnet (10.201.x.x) used for VOIP. The .1 gateway resides on an HP 5400 series switch in order to provide multicast services to a number of internal networks across our WAN. We have just installed a Cisco Express Gateway for Jabber clients to utilize VOIP services from home, across the Internet. I set up a PBR on the voice vlan to use for a gateway when calls come in across the Express Gateway and to use for a gateway when communicating with our internal networks.

A key server with IP has Trusts established for LDAP authentication to our Call managers. When the PBR is in place, the Trusts do not work for some internal domains because the .5 server is now routing to the Internet for DNS rather than looking to the local conditional forwarders to identify the domain controller of the internal network attempting to authenticate.

I know you can set up a PBR to be port specific but the Jabber client and Expressway use many tcp and udp ports to communicate. Is there a simple way to force the .5 server to resolve all DNS internally yet route all other traffic pertaining to a Jabber connection out the gateway?

Here is a snippet of what is not working:

Policy pbe 10201-routing
     150 class ipv4 "nls-1916814"
      action ip next-hop
     160 class ipv4 "kms-172"
      action ip next-hop
     170 class ipv4 "10201-Internet"
      action ip next-hop

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i have a firewall fortigate 200D
i have two switch HP in each switch ihave two vlan
vlan 1:
vlan 2:
how to inter routing vlan to ping each computer from vlan.
Hi Experts,

I have a cisco stack 2960X and I want to connect it over fibre 10G with an ARISTA switch 7050.
The problem is the 10G port is flashing amber and green.
When I check the interface on the cisco I see many runts.

How can I trouble shoot this issue ?
I tried to google around to get some answers for two cisco switches connected by two stacking modules. some people says each switch should have one uplink, two stacked switches should have total two uplinks,  however, some other people says two switches only need one uplinks. what is the correct answer?
I have a Cisco WS-C4503 chassie with two WSX-4148-RJ45V 48 ports blades.  When I connect one of my NEC VOIP phones up to the system I do not get any power to the phone from the port.  I have check to ensure port POE is set to auto.  Here are some of my configs, I assume these blades are POE since they have DC In-line on them.
Cisco_MFG#sh environment status
Power                                             Fan      Inline
Supply  Model No          Type       Status       Sensor   Status
------  ----------------  ---------  -----------  -------  -------
PS1     PWR-C45-2800AC    AC 2800W   good         good     good
PS2     none              --         --           --       --

Power supplies needed by system    : 1
Power supplies currently available : 1

Chassis Type : WS-C4503

Power consumed by backplane : 0 Watts

Supervisor Led Color : Green

Module  1 Status Led Color  : Green
Module  2 Status Led Color  : Green           PoE Led Color : Green
Module  3 Status Led Color  : Green           PoE Led Color : Green

Fantray : good

Power consumed by Fantray : 30 Watts

Cisco_MFG#sh power inlin
Available:1400(w)  Used:0(w)  Remaining:1400(w)

Interface Admin  Oper            Power(Watts)     Device              Class
                            From PS    To Device
--------- ------ ---------- …
2017-10-02-09_53_32-untitled53467h5-.pngRunning into one of those "how the ... is this working" issues and I can't figure out what up. I have a cisco 4321 ISR and a C3560CX cisco switch. Very simple config. Have a vlan1 on the switch configured as an access port to the router. Everything is working, no issues detected at the site, users are able to get out to internet, but I am unable to ping the switch from router.  Vlan is ARP is incomplete below. CDP not showing anything behind. This is my now 2nd location where this is happening. Not sure what it is. Any ideas? Bad switch maybe? It must be running someone at Layer2 at this point

RTE#sh arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet            0   Incomplete      ARPA

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RTE#sh int g0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
  Hardware is ISR4321-2x1GE, address
  Description: LAN-INSIDE
  Internet address is

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Switches / Hubs





A switch is a device that filters and forwards packets of data between LAN segments. Switches operate at the data link layer or the network layer of the Open Systems Interconnection (OSI) Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. A hub is a connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports; when a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.