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

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78
votes
2answers
80k 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 ...
18
votes
7answers
16k 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
37k 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 ...
11
votes
1answer
29k views

VLAN tags not shown in packet capture (Linux) via tcpdump

I am adding a tagged VLAN onto eth0: #ip link add link eth0 name eth0.20 type vlan id 20 This results in: #ip link 2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc ...
3
votes
2answers
5k views

How do I dynamically obtain IP addresses for VLAN interfaces?

I have an Ubuntu machine on which I have created four VLANs, namely eth0.100 ,eth0.200 , eth0.300 and eth0.400. I want to dynamically obtain the IP addresses using the DHCP server. It should provide ...
2
votes
1answer
554 views

Persistent Network Configuration using KVM and libvirt

Our environment will have a KVM host setup dynamically using kickstart (easy enough). The hard part is dealing with network configuration and keeping VLAN configuration (and possibly bridge/host ...
23
votes
4answers
13k 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 ...
11
votes
5answers
3k 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 ...
11
votes
2answers
31k 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 ...
7
votes
2answers
5k 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 ...
3
votes
2answers
5k views

Debian: Should I add vlan interface into bridge for KVM?

I am setting up a Debian Squeeze box as a KVM host. I want to add multiple interfaces to each KVM guest so I want them to be on different VLANs. After reading about this, I believe the best method is ...
8
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 ...
4
votes
3answers
12k views

Set 802.1Q tagged port on VLAN1 on Dell PowerConnect switch

I'm having big troubles when adding this Dell switch to my network. Here we use several VLANs to segment traffic. All switches (3com and DLink mostly) have configured the same VLANs, most ports are '...
2
votes
1answer
5k views

How do I setup routing for two companies with different Internet connections on the same LAN?

Here's the setup: Two companies (A & B) share office space and a LAN. A 2nd ISP is brought in and company A wants its own Internet connection (ISP A) and company B wants its own Internet ...
1
vote
1answer
959 views

CoreOS bare-metal vlan networking

I need to write a CoreOS Cloud Config file in which I need to setup networking. But i have a problem because I have a bit weird environment. What I'm trying to accomplish; I have a Sophos UTM thats ...
5
votes
3answers
942 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 ...
1
vote
1answer
106 views

Routing based on the source ip

I'm trying to configure a host in a way that the traffic is routed either via eth0 or vlan123@eth0, depending on the source address used. Both interfaces have access to the whole network and both have ...
0
votes
1answer
170 views

Cisco 877 ISR - Joining to another local network

At a remote site I have a Cisco 877 ISR providing network services (DHCP, DNS, internet, VPN back to base). I need to connect it to another companies LAN at the remote site to allow uses to print on ...
0
votes
2answers
2k views

Switch sending DHCP packets to wrong VLAN

I have a basic remote site with a Cisco Catalyst 2924XL switch. There are 2 VLAN's at the site: 1 Default 2 Wireless There is a single server connected via a single ethernet cable, VLAN 1 is native/...
4
votes
3answers
14k views

DHCP server for multilple VLANs [duplicate]

Possible Duplicate: Can I have multiple DHCP servers on one network? This is a very old question i guess.In this forum itself it has been answered in Multiple VLANs, multiple subnets, single ...
3
votes
2answers
1k views

One big subnet with all clients an issue?

Disclaimer: Network rookie, might have wrong assumptions. Got a basic subnet question that im interested in hearing your thoughts about. Subnet: 192.168.251.0/24 Address Range for servers: 192.168....
3
votes
1answer
3k views

For VLANs: difference between untagged and non-member setting for ports?

The "default" VLAN is VLAN 1, and traffic over ports are Untagged by default (at least, in the switches that we use). We've created VLAN 2 and marked the necessary ports as Tagged, and it's working ...
2
votes
1answer
2k views

D-link DAP-2590 VLAN configuration

So we have been fighting this issue for well over a year. It's been so long that I am having to relearn the configuration today. Here's the situation. We're running several D-Link DAP-2590's with ...
2
votes
2answers
1k views

Is it possible to configure a private VLAN on a switch and still access each server via a public IP?

I'm sure this is a very basic/common networking problem. I have 1 web server and 2 database servers that are co-located in a data-center. I have been issued 10 public IP addresses and I have a 10 port ...
2
votes
1answer
677 views

Managed switch port-based DHCP allocation - general case?

I saw a strange comment bagging IT departments (i.e. sysadmins) on Slashdot the other day: half the time they cant even do a simple thing like provide a jack with a set IP address for us Reading ...
2
votes
2answers
2k views

Linux is sending ARP requests to hosts in other subnets?

Setup Host B <--> Router <--> Host A Host A: IP = 192.168.1.10, Net = 192.168.1.0/24, VLAN = 1, Default GW = 192.168.1.1 (Router) Host B: IP = 192.168.2.10, Net = 192.168.2.0/24, VLAN =...
1
vote
0answers
41 views

Small business network vlans and hyper-v configuration

We are a small business and have been successfully running one Hyper-V 2012 R2 vmhost with many Windows Server 2012 VMS that includes a DC, Web Server, CRM Server and SQL Server for a couple of years. ...
1
vote
1answer
2k views

Cross-VLAN sharing and auto-discovery of selective resources

I have a network with several VLANs that each contain resources or clients with different access rights. For simplicity, let's say I have 3 VLANs: ID 10: Contains privileged clients and private ...
1
vote
2answers
1k views

Draytek 2830, Multiple VLANS on Same Port

The Kit Ubiquiti Unifi Long Range Wireless Access Point Cisco SG200-08P Switch (VLAN, POE Support) Draytek 2830VN Router The Problem I need to enable Multiple VLANS against a single port on the ...
1
vote
2answers
7k views

How to interconnect 2 switches (Cisco/Dell) with trunks

In order to migrate to a new rack inside the datacenter I have to replicate the VLAN setup between a Cisco Switch and a Dell PowerConnect Swithch. On the Dell Switch I have 2 VLANs : vlan 10 : WAN ...
1
vote
1answer
778 views

How to share multicast traffic to many vlans

I have linux computer , this computer connected with entire my network via zyxel gs-2200. In this zyxel also connected router with 500 vlans, one by client. On linux computer i have vlc program ...
0
votes
1answer
2k views

Draytek Vigor 2860 multiple external IP-addresses

I've bought a DrayTek Vigor 2860 for my company network. And I'd like to use it for two VLANs with separated external IP's. I have 6 LAN ports on my DrayTek. For example: External IP-adres: 201.102....
0
votes
1answer
1k views

Broadcast between VLANs

I have a network with 2 VLANs running on a Cisco SGE2010 with the switch acting as the gateway for each vlan: 192.168.10.0/24 VLAN 10 192.168.20.0/24 VLAN 20 Servers live on VLAN 10 and Desktops on ...
0
votes
2answers
873 views

Enabling 8021q on a nic

I'm trying to get a vlan interface on a bonded nic (Centos 5.5) and whilst the interface has been very happily created with vconfig I'm seeing no traffic on it at all. Running tcpdump and tshark on ...