a device that bridges network segments, operating at the OSI link layer level.

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98
votes
9answers
7k views

Can you mount a network switch upside down?

We just took delivery of a new Avaya 2500 48-port switch, that has 24 PoE ports. The problem is that all the PoE ports are on the left-hand size of the switch, and our PoE device cables can only reach ...
66
votes
1answer
10k views

What happens when you plug two sides of a cable to a single networking device?

What is likely to happen when you plug two ends of a network cable to a single switch/router? Will this create problems on the network, or just be ignored?
55
votes
2answers
42k views

How do VLANs work?

What are VLANs? What problems do they solve? I'm helping a friend learn basic networking, as he's just become the sole sysadmin at a small company. I've been pointing him at various questions/answers ...
49
votes
12answers
4k views

What should I pay attention to when I'm buying a network switch?

Since I'm not a hardware expert, I don't know what features make a network switch a good network switch. What should I pay attention, when I'm comparing the different models from different vendors?
44
votes
6answers
39k views

What is the difference between a managed and unmanaged switch?

I've seen some documentation discussing the use of an unmanaged switch. What is the difference in functionality/performance/etc. between an unmanaged and managed switch?
32
votes
3answers
2k views

What kind of network attack turns a switch into a hub?

I read an article today describing how a penetration tester was able to demonstrate creating a fake bank account with a $14 million balance. However, one paragraph describing the attack stood out: ...
28
votes
14answers
65k views

What is a patch panel?

What is a patch panel? How it is different from (layer 2) switch? EDIT: I think my primary question (and confusion) is this: Why don't network connections go straight to the switch? Don't we still ...
25
votes
7answers
19k views

What is the minimum ethernet cable length for a CAT6 gigabit connection?

We run a Netgear GS724Tv3 switch and part of the configuration per port is an option for "Lower Power Mode". The documentation for the switch lists this feature as a "Green Ethernet Configuration" ...
23
votes
8answers
29k views

Does using a single cable to connect two switches create a bottleneck?

I realise this may be a stupid question for some, but it's something I've always wondered about. Let's say we have two gigabit switches and all of the devices on the network are also gigabit. If 10 ...
21
votes
3answers
6k views

What happens when a consumer switch receives a VLAN-tagged Ethernet frame?

Suppose you connect a trunk port from a VLAN capable network switch to a (VLAN incapable) consumer-grade network switch via a direct cable. Now the former switch send the later switch a 802.1Q-tagged ...
19
votes
6answers
28k views

What are the implications of having two subnets on the same switch?

Can anyone tell me what some of the implications of having two different subnets on the same switch would be if VLANs are not being used?
18
votes
7answers
670 views

Power loss at company

Property management at my organization has informed me that our building will be losing power for 4 hours tomorrow. I need to be prepared for this event (we're a small organization, i'm young, ...
17
votes
3answers
4k views

Connecting two desktop switches with more than one cable?

I was hoping to find a way to increase bandwidth between two desktop switches I have, and I wondered if connecting them with two cables (or perhaps three) instead of just one might increase ...
16
votes
3answers
2k views

How does network sniffing software work over a switch?

We have several of standard non-managed 3com switches in a network. I thought switches were supposed to only send packages between peers of a connection. However it appears network sniffing software ...
16
votes
3answers
7k views

How do I know if I need a layer 3 switch?

We currently have a flat network with a bunch of unmanaged switches. I would like to use VLANs to segregate certain users like guests and I would like to use 802.1x. However, I'm not sure if what I ...
16
votes
3answers
200 views

Phones on some switches cannot complete DHCP process

Background I have a Windows DHCP server (Server 2008 R2) handing out addresses for several scopes. One of those scopes is for some Mitel IP Phones. The phones are configured to use dhcp option 125 to ...
14
votes
5answers
7k views

Why do rack switches have their ports on the front?

I've ordered some rack hardware from Dell. A 42U rack, a 3U EqualLogic SAN, two 1U PowerConnect 5424 switches, three 1U PowerEdge servers, and some other stuff such as a tapedrive, firewall, UPS, etc. ...
14
votes
2answers
2k views

How do I ground a network switch?

I read in a lot of places that it's necessary to ground networking equipment. In a small SOHO environment where there are, say, 4-5 systems and each system is grounded, is it also necessary to ground ...
13
votes
3answers
11k views

What's the difference between a switch, a router, and a modem?

What's the difference between a switch, a router, and a modem?
13
votes
3answers
744 views

Prevent administrative users from assigning duplicate static IPs to their workstations

How can I prevent a user that is an administrator on their local machine from manually assigning an IP to their network adapter that is in use on a server? Some users have done this, and it's caused ...
13
votes
1answer
2k views

What would cause SIP traffic to be seen going into a switch but not coming out?

Background I have been struggling to get my SIP phones to register behind a brand new router and switch in our brand new office. Our PBX is hosted offsite. I have worked with our provider to attempt ...
13
votes
7answers
11k views

How do you keep track of what's connected to your switches?

Currently we manually document the connections to the ports of our switches. Of course, maintenance is a chore, and the documentation is out of date as soon as you save it. Are there any tools for ...
12
votes
3answers
10k views

Is it possible to include switches in traceroute hops?

I was wondering if it's at all possible to make a Dell Powerconnect 2848 switch show when running internal traceroutes. This would help with diagnosing issues and make it far easier to see where ...
12
votes
3answers
1k views

Improvements for small business network?

My question is more-or-less a newer version of this 3 year old question: Small Business Network Switches/General network configuration Summary Everything is Gigabit and we don't have any real ...
12
votes
5answers
2k views

Small Business Network Switches/General network configuration

We just had one of our many 5-port network switches die on us and it took over a day to figure out what was causing our network problems. So now I have $200 to "fix" our network. Our goal is a ...
12
votes
5answers
17k views

The Job and Monitoring Options of RoboCopy

What does the Job Options of RoboCopy do? And what exactly does the /MON and /MOT switches do? How can I use them? I don't understand them, and can't find any examples on how to use them. ...
11
votes
7answers
32k views

Best way to connect multiple switches together

We currently have five 24 port 3com unmanaged switches. Four of them are 100Mb switches with no gigabit port (MDI Uplink port is 100Mb). The fifth is a full gigabit switch which we use for all of ...
10
votes
7answers
928 views

What's a good way to handle multiple devices with the same MAC address on one network?

The devices I'm working with come off the production line all set to the same MAC address. I can set each one to have their own static IP, and I'm wondering if there would be a way to connect them to ...
10
votes
5answers
4k views

If you turn on spanning tree, how do you know there is an issue with your network?

I have been learning about spanning tree protocol (STP/RSTP/MSTP) and was wondering, once I turn it on and it's protecting against for example network loops, how do I know there is a network loop? I ...
10
votes
4answers
4k views

Is a Network Switch IP-Aware?

I have some very trivial basic questions about networking, but I find varying information on that, so I just wanted to settle this. As far as I understand a Network Switch handles traffic ...
10
votes
3answers
467 views

Cut network cables in Cisco 2960 PoE

We've a Cisco 2960e that services our VoIP phones and other things. I inherited it. The question I have is the cut cables: there are about four network connectors that are cut about 1cm away from the ...
10
votes
2answers
790 views

Cable management strategy for a small chassis switch

I'm working with a small site buildout that contains a single HP ProCurve 4200vl chassis switch. The data cabling contractor did not provision for any cable management. I'm looking at the rack ...
10
votes
7answers
3k views

Are VLANs necessary for my environment?

Greetings. I'm the new network manager for a school. I've inherited an environment made up of several Windows servers, about 100 Windows clients, ten printers, one Cisco router, six Cisco switches, ...
9
votes
2answers
551 views

Why WakeOnLAN frames are sent to broadcast

I'm trying to figure out why wake on lan frames, in the simplest form, are designeted to the ethernet broadcast address (FF:FF:FF:FF:FF:FF) and not to the address of the machine to be powered on. ...
9
votes
4answers
3k views

How long do managed gigabit ethernet switches take to boot up?

One critical drawback that I have found in researching managed-switches, and one that I have some past experience with is that anything with "lots" of firmware is going to have lots of issues ...
9
votes
3answers
9k views

Server-to-Switch Trunking in Procurve switch, what does this mean?

I am looking to set up switch redundancy in a new datacenter environment. IEEE 802.3ad seems to be the go-to concept on this, at least when paired with a technology that gets around the "single ...
9
votes
1answer
878 views

Proper method for connecting multiple non-stackable network switches?

I deal with many clients in warehousing and industrial applications who have IT staff or local consultants. Many of these sites are still using a 10/100 Megabit switching backbone... I've managed to ...
9
votes
4answers
26k views

What's the difference between a Layer 2 & Layer 3 switch

What's the difference between a Layer 2 & Layer 3 switch? I've always wondered and never needed to know until now.
9
votes
1answer
4k views

Admin mode on Procurve Switches

Not being a network expert, I spent some time configuring my network, until I found my mistake: On my HP ProCurve Switch 1810G, I thought that "Admin mode" means whether the administrative interface ...
9
votes
2answers
6k views

Is my Cisco switch port bad?

I've been chasing a packet-loss and network stability issue for a handful of end-users on an internal network for the past few days... These issues surfaced last week, however the location was struck ...
8
votes
2answers
2k views

What is serialisation delay? Why does 10GB Ethernet help reduce it?

In the context of a network switch, what exactly is "serialisation delay"? (I've heard this term a few times.) I've also heard that 10Gb Ethernet (as opposed to 1Gb Ethernet) as a transport technology ...
8
votes
4answers
2k views

Someone crashed a whole network with a single switch

This might not be a real question, my apologies, but I'm pretty sure it will make your doomsday scenario enjoyment work a little. My company act as a contractor for a larger company. We need to plug ...
8
votes
1answer
4k views

Layer 2 Loop Avoidance: Three Switches in Series

I know this seems like a homework question, but it's actually part of a larger project (and network) and need to break it down into chunks so I'm clear with what I'm doing. I've never worked with ...
8
votes
2answers
579 views

Connecting two devices over 10Base-T Ethernet without a Switch

I am trying to connect two devices one of which is only capable of 10Mbps and does not support auto-negotiation. (The other is a black box, I am unsure how to tell whether it supports ...
7
votes
2answers
3k views

Is it possible for a gigabit switch to be PoE-powered? [closed]

I'm in need of a gigabit switch that can be powered via PoE, rather than AC power. There isn't any AC power in the area where it needs to be installed. Is this possible?
7
votes
10answers
43k views

Identify machines connected to switch

Our company recently closed down half our office space, which was not being used. We gave back the unused space to the building management and had it walled off. Prior to us closing it off, I jotted ...
7
votes
2answers
3k views

Do switches sometimes need rebooting?

In your opinion, do switches sometimes need a restart? I'm asking this because today our NAS stopped working properly, and was only fixed when we restarted the switch it was attached to.
7
votes
5answers
10k views

What is the disadvantage to cascading multiple switches?

I have to wire a new office for ethernet and the contractors want to charge atrocious amounts for each line running to each room in the office. It will be much cheaper for me to run a single line to ...
7
votes
2answers
812 views

Architecting your network when you run out of VLANs

This is an entirely hypothetical question, I'm not in this situation now. What happens to your VLAN topology and routing if you run a multi tenant network and you have more than 4096 customers? Do ...
7
votes
5answers
9k views

Is it possible to connect a single NIC to two different VLANs?

I know it is possible to assign multiple IP addresses to the same NIC as long as they are on the same sub-net (e.g. server A can be assigned both 192.168.1.1 and 192.168.1.2). However, is it possible ...