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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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Hello guys, I have a Cx that has 3 switches on their data center. The main switch is a Cisco SG300-52 switch with L3 functionality. On its port #20 its connected another Cisco SG300-52 L2 switch, which we can name it "switch B", and on its port #44 its connected "switch C" which is another SG300-52 L2 switch.

The IP of the main switch is 10.0.3.1 - the Cx says it took the default gateway as its IP automatically when changed to L3, they used to have a regular router before. IP of switch B is 10.0.3.19, and IP of switch C is 10.0.3.187. They are all working good, but the problem the network admin is having is that he can only access the main switch's web console through any access point in the network. Whenever he tries to access switch B (10.0.3.19) or switch C (10.0.3.187) through his web browser, the pages appear to be blocked. But if he connects physically (wired) to one of the switch B or the switch C ports, they can access to the web console of the switch they are wired to. So, switch B and switch C are working good, and their respective web admin consoles are fine.

What can they do to have access to their 3 switches from any access point on the network?

Thanks in advance for any help, any suggestions are welcome.

Best Regards,

Manuel
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Dear experts, if the Access switch is unconfigurable of DHCP snooping, can we do it on Core switch? (The Dhcp is on Core)

Otherwise, how can we mitigate the rogue DHCP? Thanks!
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10 Comments
I have two Cisco Nexus 9K's at my core layer both with 96 copper and then some fiber modules.

I'm having a weird issue where random copper ports just stop working. Issuing a shut / no shut doesn't help. Because I can't always reboot the core I will just move it to another port. But whenever I do get a chance to reboot, the ports will work again.

These ports have a very simple config: switchport mode access; switchport access vlan X and a description. I am not running STP on these ports.

Anyone see this before? Any insight is much appreciated.

Thanks in advance.
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6 Comments
I want to buy a 1M FlexStack Cable for my 2960s switches, but I can’t see the part number (CAB-STK-E-1M) for price estimation in CCW.
Any advice why

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-2960-s-series-switches/data_sheet_c78-726680.html

Stacking Interfaces
Cisco Catalyst 2960-S FlexStack stacking cables:
●  CAB-STK-E-0.5M FlexStack stacking cable with a 0.5 m length
●  CAB-STK-E-1M FlexStack stacking cable with a 1.0 m length
●  CAB-STK-E-3M FlexStack stacking cable with a 3.0 m length
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MPLS Layer 2 and NAT

If I understand with MPLS Layer 2 , you can connect 2 sites of your networks and will seem just like you are on the same LAN network, except for speed.

Well, let say ISP gave us MPLS L2, and we connect one of our routers of our Site1 to one end of MPLS and another router of our Site2 to the other end of MPLS.
in this case, should the interface of a router connected to Site1 have to have IP address on the same subnet as the interface of the other router connected MPLS on Site2 ?

I mean : (Site1)R1---Interface1------>MPLS-<------Interface2--R2(SIte2)
Interface1 will be on the same subnet as Interface2 ?


Assuming it should.

Now to get all networks of Site1 and Site2 to communicate, do we need NAT translation configured on Router connected to MPLS on Site1 and Router connected to MPLS on Site2 ?


Thank you
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10 Comments
how to create a google analytics segment?
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1 Comment
Is Root Bridge relevant when connecting to L3 Switches.

I would like to know when I have all my L2 switches connected to L3 (Distribution or Core) switches, if there is any concern about Root bridge election or even STP loop.
To my understanding as long as L2 switches are not connected directly between themselves there will be no Root Bridge election and there will be no STP loop to happen.
for instance in the Diagram below, all L2 switches are not connected directly between themselves, but connect to L3 switches.

Thank you

sp
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17 Comments
We have a Cisco 3560 Switch with IOS 12.2 and need to get to an IOS that can use SSH.  Can someone point me in the correct direction?
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6 Comments
I am working with a coworker on migrating a client to Exchange online. One users mailbox won't complete the migration process. We're performing a cutover migration. The user had a Office 365 account for Microsoft office already. We're migrating into that tenant. The mailbox was migrated and showed it had synchronized successfully, but the mailbox does not show up under "Recipients" in the admin console. Tried resynching it again but nothing happens.
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5 Comments
Interface Multilink Vs Interface Virtual Template on Cisco Routers

I would like to know the difference between using the commands :
Interface Multilink Vs Interface Virtual Template

it looks like they achieve the same thing.

Any idea ?

Thank you
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5 Comments
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I am connecting two sites via fiber into Cisco SG300's.

Each network has it's own subnet 192.168.100.0/24 & 192.168.200.0/24 respectfully.

How can I configure the switches to prevent the respective DHCP servers from crossing over the interconnect?
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2 Comments
adding an additional layer 3 switch to my network

i am trying to add a cisco layer 3 switch to my existing Dell Layer 3 switch, i configured the Cisco 3 switch and added my Vlans etc.

My Dell is Dell PowerConnect 6248 and Cisco is Cisco SG350X- 48MP

i enabled the Dell XG4 fiber port and turned on trunk but everytime i connect the fiber the network goes downDell Switch config1Dell Switch config2
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31 Comments
I have cisco catalyst 4507R-E that has to be replaced with below:
1. New Cisco catalyst 9407R switch with 2 supervisor modules, 1 24 sfp+ port module and 1 48 1Gig UPOE ports.

What are the recommended steps or the best way to migrate from 4507R-E to 9407R.
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0 Comments
I have a Cisco 2960x switch and a heap of Nec DT800 handsets and would like to put them on a Voice VLAN. The only way I have been able to get it working was to enable the Voice VLAN on Switchport and configure VLAN tagging on the handset as we may need to use the built in switch.

Considering they move handsets often is it a safe assumption to just apply the Voice VLAN on all the switchports just in case they move one to an unconfigured port?

What’s the best practice?
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10 Comments
Hi Here is a strange case. Anyone has an idea？ Nesus5K is connected to Nexus2K with fex. Not sure Nexus2K port is broken. When PC is plugged into the port111/1/31 or 32 etc, PC NIC and switch port cannot be up. Finally we found all ports with command “switchport access vlan 2” have this problem. Other ports are able to be up once PC is plugged into ports with command “switchport access vlan 3”. All ports are no shutdown. and its configured in all there kind of ports is very simple, with one command "switchport access vlan x " Is this switch ports problem or vlan issue, or other issue? Thank you

Plus, we just tried unused ports in N2K. we still notice some ports with vlan2 are up, but they are being used.
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13 Comments
Ports on Cisco SG300-28PP constantly doing Link up and Link down.
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3 Comments
We have Brocade 5100 switch which is failign to boot and all the ports on the switch are yellow.
I conected the console cable to the switch and saw the following output:-
The system is coming up, please wait...
U-Boot 1.1.3 (Jun  5 2008 - 23:49:03)

CPU:   AMCC PowerPC 440EPx Rev. A at 660 MHz (PLB=132, OPB=66, EBC=33 MHz)
       No Security/Kasumi support
       I2C boot EEPROM enabled
       Bootstrap Option G - Boot ROM Location I2C (Addr 0x54)
       Internal PCI arbiter enabled, PCI async ext clock used
       32 kB I-Cache 32 kB D-Cache
Board: Spirit
I2C:   ready
DRAM:  Initializing DDRSDRAM
DDR Init: speed = 132000002
DQS calibration - Window detected:
max_passing_cases = 0
wr_dqs_shift      = 0
dll_dqs_delay_X   = 0
dll_dqs_delay_X window = 0 - 0
DDR0_09=0x00011d00
DDR0_22=0x0026200b
DDR0_17=0x00005500
DDR0_18=0x00000000
DDR0_19=0x00000000
ECC Enabling
Start memory clearing @ 0x00000000 size = 0x20000000...addr = 0x10000000
addr = 0x20000000
   DONE
512 MB
 
After this there is no more output on the console.
I looked at on of the Brocade SAN Health software reports and it showed a failed power supply fan.
We had a power failure due to which this switch got shutdown and has been in the above stated status since then.
Will it be the failed power supply causing this?
Is there a way to be 100% sure that this power supply is the cause of switch not booting up as then we can buy the power supply.
What else can cause this and what …
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3 Comments
I have 1 aruba 2930F 48G 4SFP+, 2 24G POE+ 4SFP+ switches. How should I stack them?
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4 Comments
Hey guys. Hope you might be able to help me out with this sort of...unique situation.

We have two facilities. I'm trying to set up some VLANs, but there's a catch: we have a fiber connection between the two buildings that is causing some problems. Let me give you an outline of our layout.

Internet comes in from ISP to a Cisco RVS4000 router/switch, plugged into WAN. Port one has a cable connecting to the main switch (Cisco) of Facility 1 (F1), which has a DHCP server running Windows Server 2008 (unfortunately. I have a new server to setup when I'm done with this project to fix that). Port three has a cat cable connected to a fiber converter going to single mode fiber running to Facility 2 (F2) about 10 miles away. (That connection is working flawlessly. I can plug into the main switch and be on the same IP range and domain as though it's just a long cat cable, because essentially it is.) At that facility, it's plugged into port 8 of a Netgear (I know) GS510TLP and running to a TP-Link (I know) T1600G-52PS. Port 2 on the Netgear is going to a TP-Link T2600G-28MPS for VoIP and port 3 is going to a T2600-28MPS for cameras.

I created some DHCP scopes and VLANs (VLAN 2 and 3) between all this mess and got it sort of working. By sort of, I mean I can plug into the switch at F1, and VLAN3 will give me a DHCP address from the server. VLAN2 will not. In order to do so, I had to use two other NICs in the DHCP server on the ranges (4.x and 5.x) I'm needing for those …
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18 Comments
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I have network diagram where we have replace the cisco switches with Aruba switches. We got the current cisco config so we can configure the new Aruba switches accordingly. Can someone help me to share a project plan template or something similar for the implementations. All the cabling will be in place on site and all the devices, spf modules will be there.
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1 Comment
On a Cisco switch what is the best way to tell if a port or interface is enabled or disabled by using no shut pr shutdown.

Thanks
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2 Comments
I am trying to setup a port channel between 2 cisco 2960s.  

I am using the following:
Switch2#(config) int port-channel 1
 Switch2#(config-if) switchport mode trunk
 Switch2#(config-if) switchport trunk encapsulation dot1q
 Switch2#(config-if)!
 Switch2#(config)int range gig 0/45-48
 Switch2#(config-if) channel-group 1 mode active
 Switch2#(config-if)!

The problem is  I get Invalid input detected at

 #switchport trunk  encapsulation dot1q
                                   ^
 % Invalid input detected at '^' marker


Could someone tell me what I am doing wrong?
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I am facing below issue

please suggest why this is happening.

24-Dec-2015 16:14:00 %LINK-I-Up:  gi28
24-Dec-2015 16:14:01 %LINK-W-Down:  gi38
24-Dec-2015 16:14:03 %LINK-I-Up:  gi38
24-Dec-2015 16:14:05 %STP-W-PORTSTATUS: gi28: STP status Forwarding
24-Dec-2015 16:14:06 %LINK-W-Down:  gi48
24-Dec-2015 16:14:07 %STP-W-PORTSTATUS: gi38: STP status Forwarding
24-Dec-2015 16:14:08 %LINK-I-Up:  gi48
24-Dec-2015 16:14:10 %LINK-W-Down:  gi17
24-Dec-2015 16:14:12 %STP-W-PORTSTATUS: gi48: STP status Forwarding
24-Dec-2015 16:14:13 %LINK-I-Up:  gi17
24-Dec-2015 16:14:13 %LINK-W-Down:  gi22
24-Dec-2015 16:14:14 %LINK-W-Down:  gi11
24-Dec-2015 16:14:14 %LINK-W-Down:  gi36
24-Dec-2015 16:14:14 %LINK-I-Up:  gi22
24-Dec-2015 16:14:15 %LINK-I-Up:  gi11
24-Dec-2015 16:14:16 %LINK-I-Up:  gi36
24-Dec-2015 16:14:17 %LINK-W-Down:  gi40
24-Dec-2015 16:14:17 %STP-W-PORTSTATUS: gi17: STP status Forwarding
24-Dec-2015 16:14:19 %LINK-I-Up:  gi40
24-Dec-2015 16:14:19 %STP-W-PORTSTATUS: gi22: STP status Forwarding
24-Dec-2015 16:14:20 %STP-W-PORTSTATUS: gi11: STP status Forwarding
24-Dec-2015 16:14:20 %STP-W-PORTSTATUS: gi36: STP status Forwarding
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I'm attempting to connect some switches in my IDF locations to my MDF switch via SFP.

The fiber connecting each IDF to the MDF is multimode, OM3. It connects to a LANscape housing in each location. From the housing, I'm trying to connect a fiber patch cable to the SPF module on the switch.

I managed to get ONE switch working in ONE IDF by using an aqua OM3 patch cable connected to a Ubiquiti module. The only way I could get that connection to work was with a multimode fiber converter in the MDF connected to a port on the switch. SPF would not work. I've tried various SFP modules, including an SPF+ 10G multimode, a Trendnet 1.25G multimode, a generic 1.25G multimode module, and even a couple single mode SFPs, just in case. I've tried aqua OM3 patch cables, orange OM1 patch cables, various LC to SC adapters, and some yellow single mode patch cables, again, just in case. I've tried just about every single combination of the above in some fashion.

On a second switch in a second IDF, even with a fiber converter in the MDF, I can't get a link. If I remove the converter from the first connection in the first IDF, I can't get a link with any combination of the above.

I am about to go insane with this problem. This should be straightforward and easy, but it's driving me nuts.

The contractor installing the actual fiber backbone has told me it's multimode fiber, OM3, 50 microns. I suppose that might be incorrect information, but I have had no issues or inconsistencies …
0
2 Comments

Switches / Hubs

21K

Solutions

10

Content

i
The collection of articles, videos, and posts on this topic.

17K

Contributors

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.