Group of hosts with a common set of requirements connected as if on the same broadcast domain despite physical location

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45
votes
2answers
27k 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 ...
23
votes
8answers
42k views

OpenVPN vs. IPSec - Pros and Cons, what to use?

interestingly I have not found any good searchresults when searching for "OpenVPN vs IPSec": I need to setup a private LAN over an untrusted network. And as far as I know, both approaces seem to be ...
20
votes
4answers
10k views

Why do people tell me not to use VLANs for security?

As per title, why do people tell me not to use VLANs for security purposes? I have a network, where a have a couple of VLANS. There is a firewall between the 2 VLANs. I am using HP Procurve switches ...
19
votes
3answers
3k 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 ...
14
votes
3answers
3k views

How can I set up VLANs in a way that won't put me at risk for VLAN hopping?

We're planning to migrate our production network from a VLAN-less configuration to a tagged VLAN (802.1q) configuration. This diagram summarizes the planned configuration: One significant detail is ...
12
votes
7answers
10k views

How many VLANs are too few and too many?

We're currently running a netwok of 800+ PCs and 20+ servers, the network infrastucture is along the lines of Core Switch 10Gb-> Area Switch 2GB-> Local Switch 1GB-> Desktop. All running 3Com ...
10
votes
4answers
20k views

Best way to segment traffic, Vlan or subnet

We have a medium sized network of around 200 nodes and are currently in the process of replacing old daisy chained switches with stack-able or chassis style switches. Right now our network is broken ...
10
votes
2answers
14k views

Multiple VLANs, multiple subnets, single DHCP server?

At my job we are prepping to transition from multiple LANs connected over slow VPN connections to a single MAN connected over fiber, and I've got a few questions. First of all, we are planning on ...
10
votes
2answers
509 views

Encryption over gigabit carrier ethernet

I would like to encrypt traffic between two data centres. Communication between the sites is provided as a standard provider bridge (s-vlan/802.1ad), so that our local vlan tags (c-vlan/802.1q) are ...
9
votes
1answer
1k views

How can I setup vSphere so that VLAN tags are not stripped at the vSwitch?

I am trying to test a VLAN-related networking issue, so I thought that firing up a couple virtual machines would be the easiest and cleanest method to test the problem. On the vSphere server I ...
9
votes
4answers
2k views

tc u32 — how to match L2 protocols in recent kernels?

I have a nice shaper, with hashed filtering, built at a linux bridge. In short, br0 connects external and internal physical interfaces, VLAN tagged packets are bridged "transparently" (I mean, no VLAN ...
8
votes
7answers
2k 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, ...
8
votes
4answers
3k views

New network design from a noob. VLANS, IP's, hardware, etc. Any comments please

I’m currently planning a large network infrastructure for a University in Ethiopia and would like people’s comments on my planning. Please bear in mind I have never done networking before. The campus ...
8
votes
3answers
2k views

HP Procurve Issue Passing Multiple VLANs over a link

Just to start off with I am a Cisco guy that got placed into an HP project. Basic topology overview from outside in: ASA 5505 with two Ethernet connections to a 2610 switch. This switch is then ...
7
votes
2answers
1k views

How to set up VLAN network

I'm changing my network from having every device on flat network to using VLans. My problem is that we already have a lot of devices on this network(192.168.20.0/24). From theory, I read that each ...
7
votes
2answers
596 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
2answers
148 views

VLAN Inheritance?

Imagine the following scenario: Primary Switch | (VLAN 3 Port) | Unmanaged Switch (Dedicated to IPMI Interfaces) | / \ / \ Server 1 ...
7
votes
3answers
2k views

VLAN's - Planning?

Our network is a flat L2. At some point we need to (I want to, but it's not strictly my responsibility) start to VLAN it down as we're obviously going to have a lot of broadcast chatter going on, and ...
7
votes
1answer
548 views

Switches - Do I need Spanning Tree?

If I have two switches connected to one another by a fibre link, and each of those switches is also connected into a local switch, and those two local switches are linked, I'm correct in thinking that ...
7
votes
2answers
2k views

VLAN for WiFi traffic separation (new to VLANing)

I run a school network with switches in different departments. All is routed through to a central switch to access the servers. I would like to install WiFi access points in the different departments ...
7
votes
1answer
2k views

How to configure a HP Procurve network for IPv4+IPv6

The setup: We are an apartment complex with approximately 1700 units. Every apartment has internet with an ethernet plug in each. The network has 60 HP 2910al-48G switches connected to a central HP ...
7
votes
2answers
740 views

Linux Router Problem

I have a Linux based router with four interfaces (each with its own private subnet). When I directly connect a device directly (i.e. no switch, just a patch cable) to one interface and another device ...
7
votes
3answers
3k views

Cisco and Linux and Vlans

I appear to have some fundamental misunderstanding of how VLANs work on Linux, and I'm hoping the good people here can educate me. Cast: One Cisco 3560, one VLAN, and one Linux box [1]. Cisco ...
6
votes
5answers
7k 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 ...
6
votes
9answers
2k views

Need prosumer router/firewall/vpn/vlan/nat advice [closed]

Looking for a recommendation on a device (or devices I guess) to do router/firewall/vpn/vlan/nat functons for my home network. Right now, I'm doing this with an IPCop box, but I'd prefer a little ...
6
votes
4answers
835 views

Best Approach for subnetting/VLANing traffic?

Our network is currently setup with no subnets or VLANs. We are looking at going to VoIP so this needs to change before VoIP is installed. I believe that we want to use VLANs to separate Voice and ...
6
votes
1answer
5k views

Connect to multiple AP with one Wifi adapter under Linux/FreeBSD?

How can I connect to more than one Wifi access point simultaneously using a single wireless adapter? I'm currently using pfSense as my home router and I want it to connect to multiple APs wirelessly. ...
6
votes
1answer
674 views

Looking for a tool to plan network/vlan topologies [closed]

I'm looking for a tool (desktop or web-based) that we can use to plan our network topologies using VLAN's. Something capable of defining switches, and mapping VLAN's to the ports and allowing use to ...
6
votes
1answer
434 views

kvm, vlans, how to simulate a 'mirror' port

I'm working with kvm 0.14.1 on an ubuntu lucid x64 box. I've got 3 vlans configured, one that is a bridge to the host's eth1. The others are host only. I want to start playing with snort. Is there ...
5
votes
8answers
2k views

Is there a good way to programmatically configure VLANs on a managed switch?

My situation is that my company makes a product that (currently) requires the user to set up a dozen or so VLANs on a managed switch that is dedicated to the exclusive use with our product. ...
5
votes
3answers
763 views

Campus VLAN Segmentation - By OS?

We've been thinking through re-arranging our network and VLAN configuration. Here's the situation. We already have our servers, VoIP phones, and printers on their own VLANs, but our problem lies with ...
5
votes
5answers
1k views

Mixing SAN iSCSI Traffic with core network traffic, Am I asking for trouble?

I am configuring a new network and had a couple questions I am finding hard to find good answers about best practices on using VLANs to separate Core network traffic and iSCSI traffic. The switches ...
5
votes
3answers
781 views

Design Critique Needed ( VLAN & ESXi )

So this is my new "project" which consists of tearing down our legacy network and re-doing it correctly. As of now it is a mess. Production is a hogpoge of legacy servers that should have been put to ...
5
votes
2answers
891 views

Multiple vlan issue with procurve switch

I have a cisco asa5505 as my rtr/fw(10.1.3.254). I have vlan 1 and vlan 3. Vlan 1 is my default all access vlan. Vlan 3 is my Guest(dmz) vlan. I can't seem to get a dhcp ip address when my laptop ...
5
votes
1answer
195 views

In what scenarios would a VLAN not align 1:1 with a subnet?

Under what scenarios would a VLAN not align with a subnet. I've been told that genearlly they always go 1 to 1. What are some examples or scenarios, and reasons for anything besides that, and for what ...
5
votes
2answers
233 views

Do I need routing protocols on a small network?

I have a small network with 10 VLANs, mostly routed via our core layer 3 switch. RIP is enabled on the core switch, but I'm in the process of adding a second router for a couple of VLANs as our core ...
5
votes
4answers
650 views

Radius feedback from AP to WiFi client

We have the following setup at our company: a gateway PC with CentOS (gw), running Radius and some traffic filtering programs. All of our employees connect wirelessly, and we have a WPA2 Enterprise ...
5
votes
1answer
255 views

Tag/Untag VLANs from Port Perspective on HP Switch

I'm familiar with vlans and tagging, and we usually use the command line interface for our HP Layer 3 switches. I've done quite a few: vlan 10 untagged 21 I've always wondered if this was possible ...
5
votes
1answer
3k views

tcpdump: capture one of several vlans

I want tcpdump to capture VLAN 1000 or VLAN 501. man pcap-filter says: The vlan [vlan_id] expression may be used more than once, to filter on VLAN hierarchies. Each use of that expression ...
5
votes
3answers
458 views

Management Network Best Practices

I am looking at setting up a Management vlan, on which I will put all the Management interfaces for my various networkable devices (Firewall Mgmt Interfaces, Server RAC, WAP Mgmt Interfaces, etc). ...
5
votes
2answers
736 views

Cisco IOS: Segregating VLANS

I am trying to segregate the traffic on the VLANs, as one is our visitor VLAN (VLAN 3 is the guest lan). It is a Cisco 881W router. Here is my VLAN configuration: interface Vlan2 ip address ...
5
votes
1answer
498 views

Setting spanning tree link “priorities” in Cisco switches

I've got a pair of C2960G-48 switches (running IOS 12.2(46)SE, if it makes a difference) with redundant trunks in place. On these switches there are a bunch of VLANs that carry quite heavy traffic at ...
5
votes
1answer
728 views

Procurve Primary VLAN

I'm trying to depreciate usage of VLAN 1 on my ProCurve switches; 1 is unused. I understand that VLAN 1 must exist, but I want to remove it from all ports, especially trunks between switches. The ...
5
votes
3answers
849 views

Linux NIC bonding on top of vlan interfaces?

Is it possible to set up bonding(active/backup) on top of existing vlan interfaces ? Assume the following scenario: Linux Server with 2 NICs connected to separate switches iSCSI initiator + MPIO to ...
4
votes
7answers
23k views

Why does a VLAN have an IP address?

A dumb question for the majority, but I am interested to know "why does a VLAN have an IP address?" Is this address different from the default gateway? Or is this address, same as broadcast address ...
4
votes
3answers
659 views

Best way to break up a large subnet

I have ran into a 10.10.50.0/20 network that is having issues with packets dropping. They run all unmanaged switches and I imagine the huge amount of devices on one subnet is causing issues. I've ...
4
votes
3answers
742 views

understanding vlan

I have few questions regarding the functioning of VLANs: 1) Do end hosts (e.g my laptop) would ever see a VLAN ID when it is connected to a trunked or Access port ? 2) As a follow-up to 1, in the ...
4
votes
1answer
172 views

Does using VLANs in your network infrastructure cause an appreciable decrease in performance?

This is something I've never considered before and wanted the opinions of the experts. We use VLANs day in and day out for various network tasks. My modus operandi is that in general, if something ...
4
votes
2answers
241 views

Vlan Tagging at Access Port in Switch

I'm Confused from the fact that Vlan tagging is done at access port and trunk port always gets tagged packets (until its case of native vlan).But I still believe in other fact which says tagging ...
4
votes
2answers
3k views

DHCP Server with multiple scopes. Which one does it use to handout an IP?

I have 4 DHCP Scopes. 10.200.0.0 <--------DHCP Server Lives Here 10.54.0.0 10.16.0.0 10.32.0.0 A DHCP broadcast request is sent to my DHCP server. How does it decide which scope to pull an ...