Questions tagged [switch]

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

Switches (in the context of this site) are devices with multiple network ports, which allow interaction between all devices connected to these ports.

Basic switches operate at the data link layer level (in TCP/IP networks) and forward packets based on the link layer address in the packet headers. They are different to hubs in the way that hubs generally broadcast incoming packets to all other ports, whereas switches keep tables of link layer addresses they have seen at specific ports and only forward packets to the relevant ports. Basic switches are also known as layer 2 devices.

Higher grade switches can include functionality at higher layers of the OSI stack. This can range from IGMP snooping (for multicast support) and VLANs through to NAT, VPN, firewalls or even application layer functionality (web caching or proxying). Such switches are known as multilayer devices.

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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 on Serverfault relating to various networking…
Murali Suriar
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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 the right-hand side of the switch (we're…
Mark Henderson
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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?
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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?
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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?
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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.
Jon Rhoades
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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?
Kyle Brandt
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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 require 1-to-1 connections from switch to patch…
Arie K
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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: Then he "flooded" switches -- small boxes that…
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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 computers connected to switch A need to transfer…
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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 Ethernet frame. What should the later switch do?…
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What is the minimum Ethernet cable length for a Cat 6 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" feature: A cable test is performed when this is …
Geoff Dalgas
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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 issues occur. According to the datasheet, this…
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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 running on a computer attached to one any one of…
Can Kavaklıoğlu
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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 theoretical bandwidth (which I am currently not in danger…
Code Jockey
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