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45
votes
2answers
29k 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 ...
13
votes
1answer
1k 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 ...
6
votes
3answers
152 views

Cisco Dot1x Port Authentication - VLAN selected based on what domain the user logs on to on computer?

Currently my company has been bought out by another. Due to this, another two companies users will be migrating into our office. It would be super handy if we could have the vlan chosen for the user ...
5
votes
5answers
3k views

Hubs/switches taking out switches?

Here's the issue...we have a network with a lot of Cisco switches. Someone plugged in a hub on the network, and then we started seeing "weird" behavior; errors in communication between clients and ...
5
votes
5answers
2k 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
2answers
2k views

Fault Tolerance with 2 HP ProCurve 2824 Switches

Looking for some advice on our current situation. We have a full rack at a data center that contains 1 uplink to the data center distribution layer switch (we don't control this), 2 HP ProCurve 2824's ...
5
votes
4answers
302 views

Are there any statistics on the number of networks using Ethernet Jumbo frames?

I am often told by Sales Engineers and Product managers that a Layer 2 Ethernet service is not fit for purpose if the maximum supported frame size is in the 1518-1522 range (enough to support standard ...
4
votes
1answer
2k views

ESX(i) Interface Bonding ala Linux?

I'm planning to virtualize some Linux hosts that I've got, and I'm going to be putting ESXi on the physical machines. Currently, I've got two switches set up for redundancy, and I've got bonding setup ...
4
votes
1answer
484 views

LAN segregation for security reasons using VLAN

I was asked to segregate the testing environment in our network to improve our security. Our structure includes: 1 switch Dell Power Connect 3448 1 switch Dell Power Connect 2748 A few 5 ports Star ...
4
votes
1answer
309 views

Should the MAC Tables on a switch Stack be the same between sessions?

According to Cisco's documentation: "The MAC address tables on all stack members are synchronized. At any given time, each stack member has the same copy of the address tables for each VLAN." ...
3
votes
2answers
917 views

How network devices affect TTL

When I do a ping, I can see the TTL value for each packet. For every router that I insert in between my computer and the router that connects to the internet, the TTL value goes down by one. However, ...
3
votes
3answers
4k views

Access ports versus trunk ports?

Can someone please explain the difference between access ports and trunk ports on a switch? I'm starting to learn networking, and my understanding is that access ports are used to connect endpoints ...
3
votes
4answers
228 views

Switch with 48 port all PoE [closed]

We are looking for a 48 port PoE switch. My budget is around $1200. Is there any switch that is reliable for that price range?
3
votes
3answers
6k views

Network wiring template for Visio

Anyone come across a good template/symbol pack for Visio for doing network wiring, patching, switch topologies, etc.? Everything in Visio for networking is 3D, and isn't really conducive to cabling.
3
votes
2answers
1k views

Basic Cisco Switch Recommendation For HSRP WAN Redundancy [closed]

I am going to have to use HSRP for WAN failover with my two routers since a routing protocol is not being offered. In order to make sure my active router doesn't get out of sync with their active ...
2
votes
4answers
777 views

Trunk fiber ports on switches

We are planning to purchase new switches for our network. We have three buildings in the same area that are all connected by fiber. Our main building is very large and needs to be connected by fiber ...
2
votes
1answer
210 views

Sizing Switches for Storage and Production

Couple questions. Should you always completely separate the storage network switches from production switches or are VLANs fine to segment this traffic? Is there a golden rule here? How do you ...
2
votes
3answers
110 views

Network Switch for Web Application

I'm migrating a web application from a single server to a three server config, two running the database and one the web tier. I need to purchase a network switch to string these servers together ...
2
votes
1answer
1k views

ESXI 5.1 - Unable to trunk to cisco switch

I have configured my esxi host vSwitch1 to use the secondary NIC on my VMware host. On vSwitch1 configuration I have set the VLAN to 4095 which specifies to allow all VLANs. If my cisco switch port ...
2
votes
2answers
666 views

Setting up 2 x switches in a blade server (BX600) - First time

I have the following items: Primergy BX600 MMB3 10 x BX620 S4 2 x Switch Blade (PG-SW107) QNAP (TS-EC1279U-RP – QNAP) (4 x Gigabit Connections) HP Pro curve Switch (2510g-48 (JA9280-A)) Patch ...
2
votes
1answer
611 views

Networking Cisco: adding 3750 Switch to existing Stack

Can any one advise about what will happen to my existing switch stack when adding an additional slave switch? I'm trying to confirm whether this will cause a temporary outage to my network or will ...
2
votes
1answer
415 views

Connecting office to data center via Metro-ethernet

I am installing a metro ethernet link from my office to my data center. The office will have a cisco 3750 with several vlans. The data center end will have a more complicated set up. The metro e from ...
2
votes
2answers
657 views

Layer 2 segmentation and network diameter

I am studying for my CCNA. The book makes a statement that I do not completely understand: "Layer 2 segmentation at the distribution layer practically eliminates network diameter as an issue." I'm ...
2
votes
1answer
213 views

Is a Fabric Module required for a Nexus 7009, or is it part of the Chassis?

I noticed that Cisco lists separate fabric modules for the Nexus 7009 switch. If I were to simply buy the Nexus 7009 Chassis (N7K-7009), what would I need at minimum? I just want to confirm, but I ...
2
votes
2answers
605 views

Cisco Sticky Mac vs Juniper Persistant-Mac

I’m trying to figure out if there is an inherent flaw in the way JUNOS handles sticky-mac addresses across their switch-ports versus how Cisco handles them. I’ll elaborate. Below, you can see that ...
2
votes
1answer
847 views

Switch flooding when bonding interfaces in Linux

+--------+ | Host A | +----+---+ | eth0 (AA:AA:AA:AA:AA:AA) ...
2
votes
1answer
632 views

Firewall with layer 3 switch or without it?

I am trying to make a simple network architecture for a small company. One of the sites is built of a firewall (to create a DMZ, to make the VPN between the sites) and three switches, like in link ...
2
votes
2answers
1k views

How can I provision/control bandwidth allocated to devices on the LAN?

We're going to have an ISP turn up a 100 mbit circuit at our office building (multiple floors, multiple offices). We need to control how much bandwidth is allocated to/used devices on the LAN. For ...
2
votes
1answer
260 views

Simplicity vs Redundancy

Assume you are tasked with running a set of mission critical web services with a targeted up time of 99.5% To achieve this, you have two identical clusters of hardware in two entirely separate data ...
2
votes
0answers
238 views

Configuring LACP across a IBM B50G switch stack

Is it possible to configure LACP (Link aggregation control protocol) that spans across two IBM B50G stacked switches. Below is an illustration of what I am trying to accomplish. I have currently ...
2
votes
1answer
143 views

Connect Dlink xStack DGS-3420 stack to a Brocade Stack

I'm currently having difficulty determining the best way to connect a Dlink DGS-3420-52T switch stack to a IBM B50G switch stack. I have two IBM B50G switches stacked together, which then connect to ...
2
votes
0answers
187 views

Inexplicable STP Behaviour

I have a problem with a couple of Dell PowerConnect 6248 switches (latest firmware) connected to a pair of external (3rd party) switches providing Internet connectivity via HSRP. I'll post more ...
2
votes
1answer
313 views

Interaction of devices with different VLAN configurations

I have an existing firewall+switching layer which is separated into per-client VLANs, with its own numbering strategy, etc. This layer is interconnected by trunk ports such that VLANs numbered on one ...
1
vote
3answers
109 views

Switch behavior on unicast packets when the destination is unknown

Please let me start by saying I am no network expert, I am a programmer who does a fair amount of L3/4 programming. My question is that when a switch receives a packet with a destination MAC that is ...
1
vote
2answers
91 views

Avoiding switch loop

Will I have loop problems with this topology because S2 and S3 are both connected to S1 and s4 ?
1
vote
2answers
499 views

Can ISPs block IP addresses? How feasible is this?

as far as i know, most of the time ISPs change the IP address-URL association in their DNS servers, so the URL is redirected to a page which displays the user a "this site is blocked" page. if an ISP ...
1
vote
2answers
3k 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
4answers
63 views

Notification when hostile device in network (port security)

I was wondering if there was a way, that whenever a hostile device (unknown device, like a wireless router a personel member brings to the office) this would be notified to a central system with the ...
1
vote
2answers
34 views

What do other nodes do with a switch's packets the first time the packets are sent out? [closed]

I'm a total newbie here and don't know much of anything about Routing and switching, Servers and the like.. so my questions might seem very newbie but please bare with me. When it comes to Switches ...
1
vote
2answers
762 views

Is it possible to assign a VLAN to an alias of network interface in pfsense?

My goal is to build a redundant pfSense cluster (as described in this article : http://doc.pfsense.org/index.php/Configuring_pfSense_Hardware_Redundancy_(CARP) The problem is that i only have 2 ...
1
vote
2answers
130 views

servers connected to a poweredge 6248 receive traffic for their 'neighbours'

In the network we have a few vlans but at the moment I was investigating vlan2 which carries the most traffic. When tcpdumping on the eth0.2 interface, I see a lot of packets arriving which are not ...
1
vote
3answers
72 views

Windows Desktop Randomly Switches Resolution

Once per log in a specific account, Windows XP is switching to 800x600 and 8 (looks like) bit color. It then after a few seconds switches back to the regular settings. This, so far, has only ...
1
vote
2answers
60 views

LAN routing without vlan tagging?

On my old Allied Telesis router I had a single interface for internal traffic. I had multiple networks talking on this one interface. For example 192.168.2.X was vlan 1-2, and 192.168.3.X was vlan ...
1
vote
2answers
330 views

Assign all VLANs on a same port on HP procurve switch

i'm looking for this information for a few hours on the web but i still can't find the answer. I have a few HP2610 switches (no stacked) and i want to assign all VLANs to switches interconnection ...
1
vote
1answer
548 views

Is my VLAN 1 a security risk?

First of all I'm relatively new to VLANs. I have a ZyXEL GS-1524 switch and two networks that I want to keep separate, but they need to use the same router. The router is on port 22, ports 17 and 18 ...
1
vote
1answer
119 views

Netgear XSM7224S / DLink 1210-48 Static Lag (Trunk Failure)!

I need to configure a Netgear Switch(XSM7224S) and DLink Switch (DL1210-48) with two trunk ports. I did the same and created a lag (static) between them, afterwhcih a reboot was performed on both of ...
1
vote
1answer
341 views

How do I span my WAN subnet to my L3 switch using SonicOS L2 bridge mode? (Sonicwall and JunOS)

I have two sets of ESXi hosts, one set for management and one for tenants. Each ESXi host has 8 nics and four vSwitches. All vSwitches are trunked via aggregated interfaces to a pair of EX in VC mode. ...
1
vote
2answers
809 views

VLAN ingress filtering - understanding correctly and verify its functionality?

When I tag traffic wrongly on a port (to do VLAN hopping like an potential attacker) should I be able to see ingress traffic to this VLAN on the port - like by mirorring the port in question when VLAN ...
1
vote
1answer
294 views

Do you backup a single switch or each switch on a extreme summit to tftp server?

I want a backup of my switching environment, so I looked up how to backup a system configuration file.I just uploaded a configuration file to my Tftp server and it completed just fine. I was wondering ...
1
vote
1answer
166 views

Have to run auto-negotiate between clients and switch - “old” switch works fine - “new” switch results in “port flapping”?

I need some help understanding a problem we're having at work: We run Altiris/Deployment Solution and have to use auto-negotiate between client systems and our switches (Altiris apparently requires ...