Switches / Hubs




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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.

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This is using a Netgear Prosaft M4100-50G L2 switch. There are 2 VLANs on this switch, namely, vlan 10 besides 1. Ports 12, 21-35, 38-40, and 44 are on vlan 10. The rest is vlan 1. This switch is located in our remote office. There are 2 uplinks connected to this switch from our hq. The first uplink, connected to port 43, is basically uplink for vlan 1; second uplink, connected to port 24, is means for vlan 10. This logical segregation works perfectly, any port either belong to vlan 1 or 10, can grab the IP from respective dhcp servers located in hq.

2 week ago, thing changed. Users using vlan 1 ports found that they no more able to grab the IP. Their port looks like is entirely "isolated". After much checking, we were having a "workaround", that is, get in an additional 8-port switch, move the first uplink, and connect it to this 8-port switch. After that, get an additional short network cable, with one end connect to 8-port switch, and the other end to any vlan 1 port of this netgear switch. The vlan 1 operations are back to normal.

Just wondering why? How to get the netgear switch to work alone without this workaround?
Please see the netgear config as attached.

Thanks in advance.
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Dear Experts,

I recently ran into some issues with my new Switching equipment. Since cost is always a big factor in home lab toying I changed from HP ProCurve to the Ubiquiti EdgeSwitch. More specific I change my 2920-24G with a 2SFP+ and a 2 10GBe extension to a Ubiquiti ES-48 and a Ubiquiti ES-16-XG.

Since I have now more than enough SFP+ Ports for my home lab toying around I wanted to create LACP between the Node (ESX Host) and the Ubiquiti ES-16-XG to connect the node with maximum performance to the Synology DS3615xs which I also upgraded with a dual Port SFP+ Card.

Here a little schema
Now the Synology DS3615xs was very easy to setup and as you can see in the attached picture (SynologyLACP.png) seams to be working as a dynamic lacp member on the ES-16-XG.

With the vSphere 6.5 Distributed Switch it seams like a whole other story... I can't seam to find the ressources or manuals where they describe how to do it with the DS or how to get it working.

Can someone point me in the right direction?

Thanks in advance

Cam you tell me the ARP table capacity of an HP/Aruba 2920 - 24port (not POE) switch?  I can't seem find the info in any documentation and I have had no luck getting in touch of a tech with HP.
Dear Experts,

My colleague somehow remove / deleted the HP switch files.

When I turn it on, it displays this?

System is starting...
Press Ctrl+D to access BASIC-BOOTWARE MENU
Booting Normal Extend BootWare
The Extend BootWare is self-decompressing......................Done!

*                                                                          *
*            HPE 1920-8G Switch JG920A BootWare, Version 1.17              *
*                                                                          *
Copyright (c) 2010-2016 Hewlett Packard Enterprise Development LP

Compiled Date       : Jan 18 2016 09:58:32
CPU Type            : MIPS4kec
CPU L1 Cache        : 16KB
CPU Clock Speed     : 500MHz
Memory Type         : DDR3 SDRAM
Memory Size         : 128MB
Memory Speed        : 300MHz
BootWare Size       : 3MB
Flash Size          : 32MB

BootWare Validating...
Application program does not exist.
BootWare password: Not required. Please press Enter to continue.

How can I resolve this?
I have cisco 3650 and 3560G connected one to one port as trunk. Ports are gig1/1/1 to g0/1

What is the recommended etherchannel configuration from port gig1/1/1, gig 1/1/2 to g0/1, g0/2?
I am remodeling four homes.  I have  installed eight port structured wiring systems in all four.  Each wall jack (room) includes one ethernet jack, one cable jack, and one phone jack.  Everything is homerun to the utility room in the basement. Within the wiring cabinet located there, are punch down blocks and patch panels for all wires and cables. I would like to install  in each cabinet, an eight port router or switch to include an integrated DHCP server, and POE  jacks. One of these Jack's will be wired to a ceiling mounted Wi-Fi access point on the third floor in the center of the home. This device should be dual band AC 1200  or greater. Ultimately, the router or switch will be plugged into a cable modem providing Internet and telephone service. I am having trouble finding the router or switch, which needs to be small enough  to fit inside the wiring panel.  I also need an inexpensive access point device.  The cable modem will be mounted by the cable service provider outside the panel.  This arrangement will allow plug-and-play of any wired or wireless device in the home without the need for a PC  based DHCP server arrangement. Has anyone done this? Any recommendations? I need to keep this reasonably inexpensive.
Does anyone know why the switch slows down so much that the VOIP starts to have Jitter and after a reboot it works fine for a week again. The switch runs the PC's through the Phones. There are no VLAN's programmed at the moment. The switch is stock standard. Are there any settings I can change?
Hello all,

I'm having problems pinging from my data subnet ( to my voice subnet ( data subnet is connected to 0/1 and voice subnet to 0/2 on my ASA5510. I've tried adding static routes on each of the switches and enabled ip routing as well. Voice Switch has VLAN1 with ip with being the IP on 0/2 on ASA.  Likewise Data Switch has VLAN1 with ip and interface 0/1 on ASA has

Can someone please point me in the right direction?

Thank you!
I have an Engenius EAP600 which I have configured only for Guest Wifi. I wanted to separate the clients that connect to that AP to only allow internet access and block any kind of local network access. The AP is connected to a Layer3 Cisco Switch which then connects to an ASA-5505 firewall. I'm a little rusty on VLAN could someone help with the commands for the Switch and the ASA to set this up?
Hi All,

I'm currently looking at this proposal & thinking of implementing OSPF & MLPS I'd like some support with the config & any ideas of best practices?

Thank you all.
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I have a security camera project that requires a run of about 1000FT for a few cameras.

I know Cat5/6 are not options due to the 300ft limitation.  I guess I could use POE switches at 300/600/900 ft as repeaters but that doesn't sound like a viable solution.

any ideas?
Hi All,

I am putting a solution together.  A supplier has quoted 2x Cisco Catalyst 3850 with a 8x10G Fibre Module. These switches seem to be very OTT for a small 3 host vSan deployment and have quoted around 30k for the pair.

Are they any other recommended switches which are way cheaper than the above. I require only 8 SFP+ ports per switch.

Thank in advance.

My apologies if I'm unable to put the question right, I am a beginner and would not understand why Im not able to log into the redundant device. These are Cisco WS-6509-E running the WS-SUP720-3B

I am trying to do an IOS upgrade on 2 devices

Device A

Device B (Redundant to Device A)

These are Access level switches and Im using SecureCRT to log into the devices. I am successfully able to log in the Device A and back up the configs. However when trying to log in to Device B - it gives me the below error

ssh: connect to host xx.xxx.z.15 port 22: Connection refused

IP of device A is xx.xxx.z.14.

What can be done in this case? Thanks in Advance !
I have cisco 5508 lan controller and 2702i WAPs with static IP address. I want to remove static ip address and assign through cisco ios dhcp server. I'll do the following:

On cisco switch:
ip dhcp pool <pool name>
network <ip network> <netmask>
default-router <default-router IP address>
dns-server <dns server IP address>
option 43 hex <hexadecimal string>

Then go to WLC GUI and go to each AP and click "Clear all config"

On switch the ports are configured as:
switchport access vlan 111
switchport mode trunk
switchport trunk native vlan 111
switchport trunk allowed vlan 9-11, 111
spanning-tree portfast

All WAPs are in flexconnect mode.

Are these steps correct? If not, please list detailed steps. Thanks.
We have a Cisco WS-C2960X-24PS configured with 4 SFP modules running 2 separate fibre ring networks 1 with 10 comnet switches, the second with 5 comnet switches. We use RSTP to control the rings to ensure port blocking.

All worked fine until the second ring was introduced onto the switch, now we have the first ring failing to block a port upon a topology change.

I am wondering as my Cisco knowledge is 10 years out of date, are the company that setup the Cisco, correct in saying that the Cisco will block both rings using RSTP.

Many Thanks
Hi im facing a problem basically we are replacing our cisco router with asr 1001 for the internet connection.

While creating the PPPOE configuration i noticed that pppoe-client is not working on the interface which im trying to configure for WAN side interface.

I appreciate if someone has experience with regards to this router. and can guide me with the full configuration for pppoe.

Thank you
Vlans Created on Cisco Sg300 Switch not working

I have created Multiple vlans on a Cisco SG 300 switch and wanted to terminate it on olt Interfaces

my topology is - Main Mikrotik Router --> Cisco Switch --> GEPON OLT Syrotech

1) main router Mikrotik... Eth-5(router) connected to Gi-1 (switch)

2) on switch i have created 8 vlans - which are 21 to 28

3) the switch port connected to router i have made it a Trunk  

4) Switch Port is connected to OLT's Uplink port and on both ports are trunk and Tagged with 21 to 28 vlans.

5) OLT's 8 fiber ports are access ports and a single Vlan is untagged on them.

OLT port 1 - Acess port vlan 21
OLT port 2 - Acess port vlan 22
OLT port 3 - Acess port vlan 23
OLT port 4 - Acess port vlan 24
OLT port 5 - Acess port vlan 25
OLT port 6 - Acess port vlan 26
OLT port 7 - Acess port vlan 27
OLT port 8 - Acess port vlan 28    

but i cannot acsess or ping my router from olt access ports.
am i doing anything wrong ??
Hi guys,

See diagram.

In this example, the DR is elected at SVI 200 (right distro), but the transit link between the core and distro, the core will be elected as the DR for multicast.  

Is it correct to say that multicast traffic will not pass, because we are unable to send the initial join messages upwards toward the RP because the DR is incorrectly configured?
give me configuration of this topology
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Need a python script that will take backup of cisco ios switch to tftp server
I need  help on troubleshooting  'high cpu utilization' issue.
I've follow Cisco guidelines but I'm still having issues.
Anyone out there could assist please?

Cisco 2811
Version 12.4(24)T2

I've noticed one of the process is high 'IP Input'.

Router1#sh processes cpu sorte | ex 0.00
CPU utilization for five seconds: 70%/42%; one minute: 64%; five minutes: 59%
 PID Runtime(ms)     Invoked      uSecs   5Sec   1Min   5Min TTY Process
 104    60120280    44871638       1339 15.37% 14.26% 11.85%   0 IP Input        
 276    19482936      885164      22010  2.64%  1.85%  5.77%   0 SNMP ENGINE      
 163     1711248   103417269         16  2.08%  2.08%  1.84%   0 HQF Shaper Backg
 274     1629536     1682225        968  1.76%  1.09%  0.49%   0 IP SNMP          
 261     2677980    14061400        190  1.52%  1.54%  1.52%   0 GLBP            
  19     3792636     6077592        624  0.63%  0.75%  0.73%   0 ARP Input        
 275      479980      846857        566  0.55%  0.33%  0.15%   0 PDU DISPATCHER  
 263      591024    27651611         21  0.47%  0.46%  0.44%   0 HSRP Common      
 262     2992532     9810618        305  0.47%  0.41%  0.40%   0 GLBP Input      
 257     1868628      497783       3753  0.39%  0.26%  0.28%   0 DHCPD Receive    
 254      532504    14192412         37  0.31%  0.31%  0.31%   0 PPP manager      
 131     1148080      726384       1580  0.31%  0.28%  0.29%   0 CEF: IPv4 proces
 259      490716     9958006         49 …
I have solarwinds to monitor the traffic .
I see (in solarwinds) cisco fast ethernet with 100% utilization although  the top conversation appears (in solarwinds)  in small payload of traffic in KB level .
How does that occur?
Hi All,
I have been at this all day to no avail.
I am using Yealink IP Phones. The customer now wants to run his laptops with the phones. So the PC's run through the phones.
The phones use their own gateway on port 1 and the PC's use their own on port 24.
In addition to VID 1 created VID 20 for the Data on all ports and Voice on VID 50 Voice as per this example I found.
Phones and PC's are on all the ports except 1 and 24.
AlI really want to do is give priority to the IP Phones.


The phones don't work and neither do the PC's when activated.
I have also setup the phones WAN port with VID 50 and the PC port with VID20.

Any help is welcome
I have not tried tagging P1 and P24 on all 3 the VLANS.  

How to automate a cisco ios upgrade process using a script like python or any other script or any other tool
Gents, I have a bit of a quandry.

I'm configuring RADIUS on a number of HP Procurve 5412zl switches and I'm encountering an interesting issue.  I've configured a fairly basic NPS policy on a windows 2012 server and I've added the following fairly standard RADIUS configuration to the switch (I'm testing with telnet so that I don't brick my SSH access until I've got it figured out):

aaa authentication telnet login radius local
aaa authentication telnet enable radius local

When I connect using AD credentials I am able to log in but it only takes me to non-privileged mode. I can then input "enable" and input my username and password again and get to privileged mode.  When I add the following command:

aaa authentication login privilege-mode

 and attempt to login, I get an error message that reads:

"Access denied: no user's privilege level supplied by the RADIUS server"

I've attempted to research this error message but there doesn't seem to be much out there on it.  On OTHER HP switches I have been able to input the "aaa authentication login privilege-mode" command to resolve the double-authentication issue, but it does not appear to be resolving it here.  I'm assuming that I must be missing something in NPS connection or network policies but I haven't been able to find anything specific.

I did find a document for configuring NPS for privileged mode on a Cisco switch but the configuration was Cisco vendor specific.  I tried it anyway, but was not …

Switches / Hubs




Articles & Videos



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.