Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium


Switches / Hubs





A switch is a device that filters and forwards packets of data between LAN segments. Switches operate at the data link layer or the network layer of the Open Systems Interconnection (OSI) Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. A hub is a connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports; when a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

Share tech news, updates, or what's on your mind.

Sign up to Post

So heres the setup

I have a new open mesh POE switch I'm trying to plug into existing 2960 so that we can plug in some OM AP's to it.  I can plug in the OMS8 switch into the cisco with the cisco switchport in access mode for the vlan we want it on. I can run a IP scan and see that the switch indeed gets a DHCP lease, i can go to that ip in browser and get the admin interface (not allowed to log in ). But the switch never checks in with cloudtrax.  I have 4 other AP's on the same subnet that check in fine, so i don't think content filtering  (as suggested by their support) is the issue, though they say the switches check into different servers than APS.  So heres the setup


is there a way i can search for that mac on either the 3650 or the ASA to see if its getting filtered?
[Webinar] Database Backup and Recovery
LVL 11
[Webinar] Database Backup and Recovery

Does your company store data on premises, off site, in the cloud, or a combination of these? If you answered “yes”, you need a data backup recovery plan that fits each and every platform. Watch now as as Percona teaches us how to build agile data backup recovery plan.

Hi Guys

I'm looking to add in some static routes on my 2 core switches (both S4810's) which I've inherited.  I've got some existing routes which I need to mimic so I'm just looking for confirmation that I'm about to do it correctly.  Here is the entry(ies) id like to mimic on my system when I run sh ip route:-

  S    via, Vl 60            1/0        5w4d
  S    via, Vl 60            1/0        5w4d
  S    via, Vl 60            1/0        5w4d
  S    via, Vl 60            1/0        5w4d

So you can see I have multiple for a number of subnets which I need to go out of to a particular Vlan interface

I need to do the same with another subnet, lets say out of the same Vlan interface

Im thinking of running the following in conf mode:-

ip route vlan 60 permanent

Is this as simple as it looks?  Does this look correct to everyone?

Is there a good tool (free is always preferred) that I can use to get a visual representation of my Switches (HP Procurve 2620), VLANS and tagging/ untagging? It is easier for me to process visuals as opposed to CLI.

We have an extreme 220 onsite and want to be able to manage it using SSH as well as set snmp for monitoring using Auvik. we thought it was all good as Auvik can log into the switch however we cannot get it to recognize the switch via snmp and when we try and log into the switch via ssh we cannot. We are able to telnet in though.

after looking around we havn't found any super clear instructions for setting ssh and snmp on this switch using the gui.

Looking forward to some guidance,

Hey Experts, we have a Digium Switchvox VoIP Server. This past weekend our local power company had to upgrade our facilities power. We gracefully shut down everything Friday night, power was restored yesterday afternoon. This morning we have half of our phones not working as they cannot get an IP now. Our LAN and VoIP LAN are attached to our SonicWALL NSA2600, we have 3 Cisco SG500-28-p Stacked switches. What we have found so far is that any phone connected to the Master switch will not get an IP for the phone. Each desk has 1 Ethernet drop, that goes into the phone and the workstation plugs into the phone. The workstations all work fine to phones that don't work. We have rebooted the switches for good measure and nothing changes. Hoping someone can help shed some light on what the problem is.

Here is how the config on the sonicwall looks for the interfaces
Interfaces on SonicWALL NSA2600
Here is the Stack.
SG500-28P Stack
Topology is like this: N7K1 ----- N5K1 -----Opengear1(OG1). HSRP ip: in N7K1, which is connected(through N5K1) to OG1, N5K1 is layer2 there. N7K1 can ping OG1 with 97% successful rate. What can cause ping loss?  We also have N7K2---- N5K2 -----OG2. but it can work well without any issue. Thank you
Hi We can access the device Opengear by https, but cannot ping it. ACL might be a reason. In addition to ACL, any thing else can cause the issue? Thank you
Have a new 3650 configured from scratch, I'm trying to get ssh/radius authentication setup.  I went through a guide to setup on switch, I have several others that are working so i know the server is setup correctly, but when i try to use it on the switch, SSh works, and i can log in with local creds, but AD creds don't work. Thinking I'm missing something.  was hoping someone could take a look over my config and see if anything stands out.. Thanks
Hi Here is Opengear IM4216. I could not find relative document on it. Is it layer2 or layer3 device? What kind of device is it? Thank you
Hi there, am looking for some assistance on an issue i cannot figure out
We have a Juniper SRX210 which i have configured a new interface on and connected a managed switch to this interface
The switch has an IP in the same range as this new interface
I can ping the new interface of the Juniper IP from the LAN interface but i cannot ping or browse to the new switch
There is no security zones setup and this works on another site in this format with the same model Juniper
I didnt set this up and have no experience with Juniper so any assistance grateful!
Free Tool: Path Explorer
LVL 11
Free Tool: Path Explorer

An intuitive utility to help find the CSS path to UI elements on a webpage. These paths are used frequently in a variety of front-end development and QA automation tasks.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.


We have a single catalyst 4500 in our datacenter. It's a WS-C4507R+E with an ipbase license. It has
2x48 10/100/1000BaseT Premium POE blades,
2x4 Supervisor 10GE (SFP+), 1000BaseX (SFP) blades in active & standby hot,
1x12 1000BaseX (SFP) blade and
1x12 10GE (SFP+) blade.

In the interest of replacing this EOL switch, I am looking for a replacement which will last 10-15 years which can easily handle this environment with the possibility of growth and scalability to accommodate modern servers coming with 10GE NICs. I'm also interested in having it in HA mode.

We also have 2960S in stacked an unstacked modes connected to this 4500 via fiber. What can be a good replacement for them also?

Thank you.
An interface on a Cisco switch show Total Output drops is 776, txload 4/255. What does it indicates ? Does it tell something wrong for the cable or the device connecting to the switch ? How to improve this situation ?


GigabitEthernet1/0/14 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 381c.xxxx.xxxx (bia 381c.xxxx.xxxx)
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 4/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 776
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 44000 bits/sec, 73 packets/sec
  5 minute output rate 1821000 bits/sec, 152 packets/sec
     3457773 packets input, 964760961 bytes, 0 no buffer
     Received 31107 broadcasts (19813 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 19814 multicast, 0 pause input
     0 input packets with dribble condition detected
     4206341 packets output, 4232934589 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     0 …
I am upgrading the Comware 5 firmware on HP 5120 switches HP 5120-48G-PoE+ EI Switch Product # JG237A. In the past I have upgraded them with they are offline.  I would use my laptop as a TFTP server, connect it to a port on the switch, and put my laptop IP address and switch management IP address on the same subnet. I would use the following commands (for example):

delete /unreserved flash:/<firmware>

tftp <IP Address> put flash:/<firmware>

boot-loader file flash:/<firmware>



Would I be able to do this with a live HP 5120 switch connected to the production network and grab the firmware off a live tftp server on the production network?

Please help. Thank you.
Hey guys,
I am dealing with a client that has been down all yesterday as well as today with conflicting IP addresses.  I worked with Microsoft and they were able to find the mac address of another device that was giving out DHCP.  I have tried arp on various servers and could not find that mac even after pinging the broadcast address.  I have tried this command: show ip arp vlan (vlan number) | include (mac address) and all that it can really tell me is what the originating port is.  This lead me to two HP switches which also have the mac address but that list the trunk port as the originating source. I am getting absolutely no where with finding this.  Please help!!!!
I need to update a bunch of catalyst switches from TLSv1.1 to TLSv1.2. Also need to disable older ciphers. Has anyone implemented this before?

Please share the steps as I can't seem to find anything documentation online for this.

Thank you.
We have a c3750-48PS the switch works fine on the computers, but the Access Point doesn't come up, it lights up, but it doesn't see the Wireless Controller. The Access Point is a 2802I.

Any ideas?
Hey guys,
We have just acquired a client that uses Cisco stuff.  I am looking at the show run file for one of their devices.  I see non default vlans added to the ports, but I don't see any list of vlans.  Somewhere at the top of the file I see, "vlan internal allocation policy."  The stuff that I am reading about it is confusing, but it seems that what this is doing is importing vlans from another device.  Is this correct?
One of a AP connecting to a Cisco PoE switch always loss heartbeat and resume later automatically.

I have checked the interface of the switch connecting to this AP, and it shows a high values in the interfaces. Is it indicated an issue in the switch physical interface or the AP itself problem ? How can I further identify the problem ?

How does Cisco licenses and support work?  I want to buy a 3850 PoE switch here in US (Amazon?), configure it here, and ship it over to Canada.  
Does it affect support or licenses at all because it will be in diff country?  

Also can someone explain the quote for me?  Besides the hardware price I have these:
- CISCO Cisco One Foundation Perpetual - Catalyst 3850 48-port
- CISCO SNTC-24X7X4 C1 Cat 3850 48 Port Full PoE
- CISCO SWSS UPGRADES C1 Foundation Perp Cat3850 48Prt

These three things are doubling the price of the hardware.  Which one of these SmartNet and what's the other stuff?  Do I need it?

Sorry too many questions.  VAR being vague on that.  Thanks in advance!
Free Tool: Subnet Calculator
LVL 11
Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

We had a new 4500x switch that was a boob (bad out of box).  It had and enterprise license however when Cisco replaced they gave us a unit with only IPBASE.  We have obtained the license file and thought there was a way to just copy and past or do CLI activation instead of having to upload the file.  Can this be done in lieu of upload?
The 3750G (v12) is issuing dhcp to a bunch of voip phones.

When I connect another segment into the switch (for a maintenance workstation), that segments DHCP server is in competition when a DHCP request comes in. Oddly enough it replies faster than the one on the switch which itself seems odd but that's yet another subject.

The question is how can I block DHCP activity both ways on a single port of this switch?
Hi I have a question when configuring Catalyst 4500.  I am trying to find the command, which needs tacacs first. and if tacacs is not available, it needs local? Anyone can help and show me? Thank you!
Hello - we have EMC Brocade DS-300B switches that are in place for an EMC storage array, and we're wanting to use the extra open ports on the Brocade switch to allow fibre transmission speeds between a couple servers as well.  But we're told these are "basic switches" incapable of Ethernet over fibre.  We're looking for the experts to weigh in on this, and if this is correct, is there anything we can do to "upgrade" the switches to be able to do Ethernet over fibre?  If there is nothing we can do, what switch model is recommended to do what we're looking for?

Thanks very much!
Still learning...
Some time ago I added web logon creds to this 3750G and I cant remember them. How can I clear those creds so they aren't needed or reset them to something I will write on the darn thing?
Switch#show run
Building configuration...

Current configuration : 1486 bytes
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
hostname Switch
no aaa new-model
switch 1 provision ws-c3750g-24ps
system mtu routing 1500
spanning-tree mode pvst
spanning-tree extend system-id
vlan internal allocation policy ascending
interface GigabitEthernet1/0/1
interface GigabitEthernet1/0/2
interface GigabitEthernet1/0/3
interface GigabitEthernet1/0/4
interface GigabitEthernet1/0/5
interface GigabitEthernet1/0/6
interface GigabitEthernet1/0/7
interface GigabitEthernet1/0/28
interface Vlan1
 ip address
ip classless
ip http server
ip http secure-server
line con 0
line vty 5 15

Open in new window

Found a post that suggested a "Skinny" install meaning no GUI installed. If true - why a prompt? Can I add it?
Directory of flash:/

    3  drwx         192   Mar 1 1993 00:19:54 +00:00  c3750-ipbasek9-mz.122-55.S         E11
  510  -rwx        1486  Mar 24 1993 20:55:35 +00:00  config.text
  511  -rwx          24  Mar 24 1993 20:55:35 +00:00  private-config.text
  512  -rwx        2072  Mar 24 1993 20:55:35 +00:00  multiple-fs

32514048 bytes total (16817152 bytes free)

Open in new window

In addition, can this switch become a DHCP server?  I dont believe so as the doc mention considerations when the switch receives DHCP config - but nothing on creating them. But I need to ask.  I will need a simple DHCP server for this assembly (SIP Phones using Free PBX) and using the switch would be ideal if it did work like that.
I am having an issue with our Idrac connections to teh Dell Open Manage plug in for vCenter. I have a seperate vlan for idrac's for 8 hosts. I am able to ping the idrac's IP on VLAN 300 and its gateway. I can connect from other vlans using the WUI. But, when i try to run the Inventory Scan for the Dell Open Manage tool, they all fail to connect to idrac's.  The credentials are all correct as i am able to get to the idracs from a browser. Has anyone experienced issues getting DOM to connect?  The DOM virtual appliance is on a different VLAN 100, but when creating connection profiles, it can detect esx hosts that are on a different vlan 200.  

Any thoughts are appreciated.

Switches / Hubs





A switch is a device that filters and forwards packets of data between LAN segments. Switches operate at the data link layer or the network layer of the Open Systems Interconnection (OSI) Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. A hub is a connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports; when a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.