Questions tagged [vlan]

For questions about Virtual LANs (VLANs) which are used to divide what otherwise would be a single OSI layer-2 broadcast domain into multiple, logical OSI layer-2 broadcast domains.

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Passing Traffic through Traffic Management Device in transparent mode

We would like to pass traffic tagged (in the same vlan) from Router_1 to Router_2 throught a Traffic Management device (in transparent mode). Now, we are using two switches (running and aimed config ...
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  • 501
8 votes
4 answers
8k views

How do I set up a VLAN between an ESXi VM and Physical Hardware? [closed]

First of all, I am a total noob. The extent of my VLAN experience is setting up a guest network on a wireless router. I have recently gotten a request to set up a public network requiring filtering ...
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  • 81
12 votes
2 answers
7k views

Tracing TCN Messages in STP

We have about 20 vlans on a L2 network running Rapid PVST+ where the root bridge is a stack of Cisco's 3750 switches. I am a bit puzzled by the number of TCN notifications I receive on the switch.. ...
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  • 894
15 votes
3 answers
7k views

Configure Cisco ASA in Transparent mode: Layer2 DMZ w/ Vlan translation

I am in the middle of a project to migrate some existing switched ethernet dot1q trunks behind an ASA firewall... these trunks have five vlans each (numbered 51 - 55). This is a simple drawing of the ...
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14 votes
3 answers
48k views

How to Monitor Vlan Traffic?

We have migrated to a new ISP who provide us several services (Internet+VoIP+VoD) and have divided each service in one vlan 100,101,102 respectively. Now I'm looking for a solution to monitor each ...
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  • 2,018
5 votes
3 answers
788 views

VLAN that mimics unmanaged desktop switch

I would like to replace a simple five port unmanaged desktop switch with a VLAN on our HP 5406 zl. I need to distribute our Internet connection to two firewalls and figured I could do with one less ...
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4 votes
2 answers
2k views

Some question about the relationship between VLAN , DHCP and subnet

I am new here and very interested in computer networks. From a book, I have some questions, for which I need help. question1: Can there be only one working DHCP server in one VLAN? question2: Can ...
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  • 141
11 votes
2 answers
2k views

Handling VLAN based MPLS circuits with site specific internet access

I'm having difficulty wrapping my head around how to set this up and the MPLS vendor is being no help so I figured I would ask here. I have a 2 node MPLS each site having internet access on the same ...
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  • 111
5 votes
3 answers
3k views

Is a router always necessary to link two subnets?

I am thinking especially of VLANs, which represent separate subnets that may need only one switch.
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11 votes
11 answers
4k views

Locate a host on Network

What is the best method of locating a particular workstation on a VLAN ? I sometimes need to do this, if a workstation IP address, shows up on an ACL Deny torrent use High bandwidth usage (Top ...
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  • 467
5 votes
2 answers
37k views

tcpdump (-i any) with vlan

I have a question regarding tcpdump (capturing all interfaces) and a strange capture I see. Environment: 2 Linux devices connected and configured with VLAN TAG (802.1q). I am pinging between the 2 ...
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  • 51
4 votes
4 answers
1k views

Can a VLAN bridge be used to replace a bypass switch with an IPS device?

I am wondering if it's possible to set up a way to remove the need for a bypass switch when using an IPS device. To summarize, I would have an IPS device acting as a virtual wire on a connection I'm ...
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6 votes
3 answers
4k views

How to throttle speed for a particular computer with high activity?

We're in an office environment of about 50 people. A few departments send emails with large attachments extensively and doing so clogs up the WAN connection (10Mbps). I'm upgrading the networking ...
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4 votes
2 answers
2k views

Super Aggregated VLAN vs. Q-in-Q

Is Super Aggregated VLANs Brocades version of Q-in-Q? If any, what are some of the major differences between SAV and Q-in-Q?
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24 votes
5 answers
29k views

Accidentally Removed Allowed VLANs from Cisco Switch Dot1Q Trunk

I am adding a new VLAN to an existing trunk port between two Cisco Catalyst switches (3750's). In the process of adding the new VLAN, it appears that I've removed the existing allowed VLANs on the ...
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  • 8,248
13 votes
3 answers
2k views

VLAN and subnet relationship

Many have pointed out that a VLAN can hold one or more subnets. If your default gateway for this subnet is on a router or a L3 switch then how could there be more than one default gateway in a VLAN ...
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  • 1,005
3 votes
8 answers
1k views

Trunk port or access port?

In a colo/DC environment, if you had a customer wanting to do their own VLANs & subnetting, would you configure the port going to their L3 switch as a trunk port or an access port?
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39 votes
13 answers
68k views

Difference between Subnet and VLAN?

You often hear the terms Subnet and VLAN used interchangeably. With the ubiquitous nature of IP these days, when are the two not considered roughly the same from a high-level, understanding that ...
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17 votes
8 answers
18k views

When *not* to create a SVI for a L2 VLAN?

When creating VLANs for just L2 on a switch -- routing will be handled by a device within that VLAN such as a load-balancer -- it isn't necessary to create the vlan interface. As a matter of habit, I ...
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21 votes
7 answers
32k views

Introductory level explanation of VLANs

What's the basic use case(s) for VLANs? What are the basic design principles? I'm looking for something like a two paragraph executive summary style answer so I can determine if I need to learn ...
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7 votes
4 answers
5k views

Are multiple links with different VLANs between two switches possible?

I'm not considering Etherchannel or LACP. Given 2 Ethernet switches A and B, where both switches have port 0 configured as a tagged trunk for VLAN 100 and 101 and port 1 configured as a tagged trunk ...
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  • 753
20 votes
10 answers
5k views

Easily deploying new VLANs in a large environment

How do people handle the need to add VLANs to all switches on their network (or even a subset of devices)? We are adding around 6 new VLANs per week at the moment and as the network grows this is ...
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  • 1,675
5 votes
2 answers
2k views

Migrating from VLANs to MPLS on JunOS [closed]

I'd like to see a worked example of recreating a regular common VLAN based topology using MPLS on Juniper hardware. In particular we will be using EX3xxx and EX4xxx for swicthing, though I don't think ...
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  • 1,675
13 votes
3 answers
35k views

Mac-flap due to roaming clients on wireless

We are running an Aerohove wireless network (controller-less).. I occasionally get mac-flaps within the VLAN tied to a SSID. I know this is coming from a roaming client.. The problem is that the ...
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  • 894

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