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Switches / Hubs

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Solutions

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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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Okay, here in my lab I have an MTU issue that I am facing.

I need to know if setting the "system mtu routing 9000" on my Cisco switch will allow jumbo frames in the network. Becuase currently it is working but not working everywhere. or to better put it they are not working when communicating with one VMware server. it is very intermittent. from one place in the network it will work and from the other, it won't.

so ping from the VMware switch to my storage device. I get the following.

""ping 10.100.0.200 size 1500
 Pinging 10.100.0.200 with 1500 bytes of data:
----10.100.0.200 PING statistics----
4 packets transmitted, 0 packets received, 100% packet loss
round-trip (msec) min/avg/max = <10/<10/<10""

But ping with 1400 will work just fine. Now if I go to the storage device and ping the same way it working fine, pinging the switch works with no problems.

Any thoughts on this.
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One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

We just purchased a Synology NAS, model RS4017xs+, and will be connected to our Cisco Nexus 93180-YC-EX switches. What kind of 10G SFP I should purchase for the Nexus? I got the data sheet from Cisco, but there are over a dozens to choose from, so I'm a bit confused. Any input will be greatly appreciated. TIA.
0
I am setting up 62 Cisco SG350 switches and can't seem to find a way to set a default gateway with a static IP address so the DNS will resolve.
0
I've looked for quite a while now with no luck.
I have SG300-20 switches which also report they are SRW2016-K9 V02.
What is the latest firmware release that's compatible with these switches?
A link would be great (for the answer, not the firmware)!
0
I have a client experiencing voice quality issues and their voice vendor is asking us to perform some Wireshark packet captures.  They have a Netgear GS724TPv2 PoE switch, which supports port mirroring, so according to NEC's instructions I mirrored the ports the PBX and IP phone are connected to and made the port my laptop is connected to the probe port.  I run the captures, making test phone calls from the IP phone, but NEC is saying the captures aren't showing any SIP traffic to/from the PBX and the IP phone.  

I don't run packet captures very often so I'm hoping an expert out there can confirm if the configuration I am running the captures in is correct?  Thanks in advance!
0
Connecting a Switch to an existing Switch

sw
I have this topology above, all switches are running RSTP
on Switch5 I have disabled the interface linking it to Switch1, so that when I re-enable it I will see the topology change (Amber Lights)
After I have re-enabled the interface on Switch5, I was able to see all interfaces on Switch3 turning Amber, except the one connecting it to Switch1, as shown below.
Though  I was not fast enough to take snapshot and Switch3 interface connecting it to PC3  was in fact also  Amber .

when Switch3 interfaces turned Amber , means there was a Major disruption in the Network for  few seconds before the convergence completed. This means  it caused some screaming in the environment

sw

My Question here is , if each time we add  a new switch  there will be this issue..Then how can we prevent that ? Especially if the existing environment has already this type of Switches design and we cannot change the Design ?

Thank you
0
Understanding Topology Change Notification on Switches

Reading this article:https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/12013-17.html#anc12
If I am getting it right TCN can also be caused by the Hosts that are connected to Access Switches, the article states that this can be avoided by configuring Portfast on interfaces to which the Hosts are connected to .

As far as I know, not all environments configure Portfast on the Interfaces where Hosts connect to, at least the environment where I work. However there is no issue reported even if there was TCN .

Any Switch Expert to shade some lights on this topic.


Thank you
0
I have a network with Cisco Catalyst 2960X switches. We are rolling out a new phone system in phases. We want to keep the old system in place as we put in the new phones. To this end, we need multiple voice VLAN's. Another question on here pointed to a solution using MAC Authentication Bypass, but it did not give an example configuration. I am not familiar enough with the VoIP side to configure this, can someone please assist? (BTW, the other phone system is Allworx.)

https://www.experts-exchange.com/questions/29020081/Multiple-Voice-Vlans-on-Cisco-switch.html
0
I have a Nexus 7k and two modules are overheating. Module 1 got all the way to 119c and
powered itself down. When module 1 went down module 4 decided to heat up and got to
104 as you can see below. The data center people supposedly moved around some insulation
to get better air to it but I'm not seeing an impact. I should probably open a TAC case but I've
been up many hours and just hope to work at this again in the morning. Perhaps one of the
experts here might have another thought? Is there any way this could be the fault of the
equipment based given the PS looks good, the fans look good etc?

4        MAC0Sn0(s2)     115             105         47         Ok
4        MAC0Sn1(s3)     115             105         48         Ok
4        MAC0-Buf0(s4)   115             105         55         Ok
4        MAC0-Buf1(s5)   115             105         56         Ok
4        MAC0-Buf2(s6)   115             105         68         Ok
4        MAC0-Buf3(s7)   115             105         70         Ok
4        MAC1Sn0(s8)     115             105         42         Ok
4        MAC1Sn1(s9)     115             105         44         Ok
4        MAC1-Buf0(s10)  115             105         47         Ok
4        MAC1-Buf1(s11)  115             105         67         Ok
4        MAC1-Buf2(s12)  115             105         50         Ok
4        MAC1-Buf3(s13)  115             105         44         Ok
4        Fwd0Sn0(s14)    115             105         87         Ok
4  …
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Hosts MAC address Replication between  Switches

Screen-Shot-2018-04-04-at-8.24.42-PM.png
I would like to know for  instance if I check the Mac address table of all 4 Switches in the topology above , may I find the mac address of PC1 and PC2, or do I need to generate traffic , ex: ping from PC to PC ? OR the mac address of both PCs can exist only on the Switches they are directly connected to ?


Thank you
0
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Connecting L2 Switches to L3 Switch

swIn the topology above I have 6 Servers , each server has 2 Nics teamed up. each Nic is connected to a separate L2 Switch. The Back of Each L2 Switch, assuming it has only one Fastethernet which is connected as Trunk  to L3 Switch.
On L3 Switch there are 6 Vlans in addition to Vlan1. I have 6 SVI , each one will be configured as the Default Gateway of each server.

I posted this Diagram just to see if this is how Servers with teamed Nic can be connected to L2 and L3 Switches. There is redundancy at the Servers level as well as L2 Switches, but not at L3 Swicthes (It is Ok since It is not time yet to talk about FHRP)

I have attached a diagram file if you need to correct it and post back.


Thank you
Vmware-Cabling-Charts2.xlsx
0
I have a cisco  and a cisco router where I am trying to run router on a stick. I built the following configs below. Ping works great but when I IP hosts they cannot connect and I cannot connect to them. They are all connected to the same switch which is connected to the same router. Can anyone give me any clues on what I am doing wrong here.

[code][/


                                    CISCO SWITCH

Current configuration : 2322 bytes
!
version 12.2
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname SW1-CORE
!
enable secret 5 $1$gJl9$2ohrNMmWR0t32wcyH1VCe/
!
username tut
no aaa new-model
switch 1 provision ws-c3750e-24td
system mtu routing 1500
ip subnet-zero
!
!
!
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
interface FastEthernet0
 no ip address
!
interface GigabitEthernet1/0/1
 description Trunk-to-Router
 switchport trunk encapsulation dot1q
 switchport mode trunk
 spanning-tree portfast trunk
!
interface GigabitEthernet1/0/2
!
interface GigabitEthernet1/0/3
 description Trunk-To-Router
 switchport trunk encapsulation dot1q
 switchport mode trunk
 spanning-tree portfast trunk
!
interface GigabitEthernet1/0/4
!
interface GigabitEthernet1/0/5
!
interface GigabitEthernet1/0/6
!
interface GigabitEthernet1/0/7
!
interface GigabitEthernet1/0/8
!
interface GigabitEthernet1/0/9
!
interface …
0
I'm setting up a set of SG300 switches to support an added VLAN and to support  LAGs.
The LAGs should trunk the VLANs.
A simple case would be like this
Upstream (3-port) LAG Trunked <> Switch <> All of the other ports Trunked.

This is what I see::THis looks OKYet, when I've tried to set this up, the Port VLAN Membership shows like this:VLAN 100 is Tagged in LAG1 - seems rightAnd, it appears that the VLAN 100 is tagged on LAG1
But, the ports belonging to the LAG (16,17,18) are sowing Excluded in Port to VLAN hereIs this normal?Is this last one normal?
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Preventing  Switch Loop

I believe that Best Practice is that Access Switches should only connect to Layer 3 devices such as  Routers or High end Switches(6500) that use VSS or  Nexus Switches.
However sometimes Access Switches connect to other Access switches in the chain before they get to High end Switch (6500).

I wonder in this case if you have Access Switches connected in chain , whether  you need to configure the closest Switch to the High end switch(6500) as a Root Switch for all VLANs ?


Thank you
0
Hi guys

I need to set up port mirroring for around 4 of our VLAN's. At the moment we have VLAN1 (default), VLAN 2, VLAN3 and VLAN10.

I have a stacked Cisco 3750x switch. There are two of them. I want to do port mirroring for each of these VLAN's  on the second switch.

So when I run 'show ip int br' i can see that it displays the second switch with the interface name 'GigabitEthernet2'. I want ports 13-7 to have port mirroring for each of those VLAN's above.

What commands would you run to make that happen?

Thanks for helping
Yashy
0
I am trying to determine if a policy based routing rule is being hit.

ip access-list send-to-pbr
  10 remark Send traffic for PBR logic
  20 permit ip address group voodoo1 any
  30 permit ip address group voodoo2 any

route-map internet-pbr deny 10
  match ip address bypass-pbr
route-map internet-pbr permit 20
  match ip address send-to-pbr
set ip next-hop 172.16.1.1

Should show access-list send-to-pbr display hits occasioned by the pbr?
Should I be able to see this with show route-map internet-pbr?

I tried the latter and get an error message about stats not being enabled.
sho route-map internet-pbr pbr-statistics
% PBR statistics is not enabled for given route-map
0
Configuring 2  SVIs with the same IP Addresses in 2 Separate Switches.

Just  want to verify if  this is doable:
let's say we have ESX host with Network adapters teamed up, and each Network adapter is connected to separate switch (same Vlans) , on each Switch the SVI (Switch Virtual IP address) is the default gateway for ESX Host using the teamed NICs.
Example

ESX Host 1 has NIC1 and NIC2  teamed up with IP address : 192.168.12.80
NIC1 is physically connect to Switch 1 and NIC2 is connected to Switch2
on Switch1 we configure SVI with IP address 192.168.12.81 and on Switch2 we configure SVI with same IP address 192.168.12.81

ESX Host Default Gateway : 192.168.12.81

OR

 we have to give 2 different IP addresses for each SVI? for instance


Switch1 SVI: 192.168.12.81
Switch2 SVI : 192.168.12.82

in this case what would be the ESX Host default Gateway ?

Thank you
0
am new to ccna ..i had small scenario attached and config mentioned below

Switch#show running-config
Building configuration...

Current configuration : 1565 bytes
!
version 12.2(37)SE1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Switch
!
!
ip routing
!
!
!
spanning-tree mode pvst
!
!
!
interface FastEthernet0/1
 no switchport
 ip address 192.168.1.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/2
 switchport access vlan 10
 switchport mode access
 switchport nonegotiate
!
interface FastEthernet0/3
 switchport access vlan 20
 switchport mode access
 switchport nonegotiate
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
interface Vlan10
 …
0
So our network has been running as is for several years without any problems until I tried to install a new switch the other day. So the other day I configured a new Cisco 2960x then added it to the network. When I first added the switch I had made a mistake and there was a IP conflict so I changed the IP and all was well, so I thought. The next morning I noticed that my VMWARE cluster was giving me an error for not being able to reach it's isolation address. I know it uses the default firewall/gateway(ICMP is allowed) so I tried to ping from the ESXi server but I was not able to . I then tried to ping from my system and I was able to ping the gateway. All of these systems are not the same network but different switches so I tried another system on my switch and I could not ping. I also tried from all of the switches with no luck.

So at this point I am unable to ping the gateway from anything but my system and the only difference is I am using a static address but so are the switches. The strange part is I would have never noticed this if it wasn't for VMWARE as everything is working normally and traffic is being routed through the firewall/gateway. I looked at the ARP tables on the systems and switches and the MAC is correct on all for the gateway. I also did a scan for duplicate address but none were found. I even rebooted the switches with no luck so I am a loss at the moment. I am not a network engineer but I get to play one at work from time to time so any help is …
0
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Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Native Vlan Commands

I have seen the following commands  used on Cisco Switches.
example:


At the interface level:  Switchport Trunk native vlan 10

At the Global configuration :  Vlan dot1q tag native

what is the difference between both commands ?

Thank you
0
Hi Experts,

I have to create a new link from my fibre box to my switch.
This is single mode and the cable is an LC-E2000 cable.

I am not able to bring the link up.

I am using the switch C2960X with Singlemode transceiver. But this is not the original transceiver it is a cheaper one.
But in the config the transceiver is visible.

CONFIG:
Gi1/0/41                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/42                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/43                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/44                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/45                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/46                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/47                     disabled     1            auto   auto 10/100/1000BaseTX
Gi1/0/48                     connected    1          a-full a-1000 10/100/1000BaseTX
Te1/0/1                      disabled     1            full    10G Not Present
Te1/0/2   "VPLS Internet Upl notconnect   1            full    10G SFP-10GBase-LR
Fa0                          disabled     routed       auto   auto 10/100BaseTX
RZ-MPLS-Switch#

Open in new window


Do you have any ideas ?
0
I have an additional sonic wall router that is setup for two separate subnets. I have a fiber to Ethernet converted connected to the wan port. I have the other side of the fiber connected to a Cisco switch on my existing network. I need to allow internet traffic out to one of my existing public ips (which i have the static configured on my Sonicwall). How do I setup the switch port to “bypass” or go out to my existing Cisco router. I hope I make sense of this.
0
Hi,

I saw in the server room there is "One Empty switch" (100% empty; no cable is attached to it).

Question: Why they prepare "the empty switch" in the server room?

tjie
0
Hi – so we have about 20 Cisco 10/100 switches at 1 location, that we are looking to upgrade to gigabit. The models we have currently are 3750-24PS-S and 2960-24PC-S, and we haven’t decided which ones we are going to upgrade to yet (if anyone has suggestions, I’ll take them) About 15 years ago I used to manage some switches at an office where I worked, but I’ve totally forgotten since then. When we upgrade, I’m assuming we can copy the running config from each old switch, copy to the to new switch, and everything should work? All help and suggestions are greatly appreciated.
0
qConfiguring 802.1 Tunneling Q-in-Q

I have the topology above. I  configured  Q-in-Q, however I cannot ping from R1 to R2 as it is supposed to.

R1#sh run  
Building configuration...

Current configuration : 1756 bytes
!
! Last configuration change at 15:08:00 CET Mon Mar 12 2018
!
version 15.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
aqm-register-fnf
!
!
no aaa new-model
clock timezone CET 1 0
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!         
!
!
!
!
!


!
!
!
!
ip cef
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!         
!
redundancy
!
!
! 
!
!
!
!
!
!
!
!
!
!
!
!
interface Ethernet0/0
 no ip address
!
interface Ethernet0/0.12
 encapsulation dot1Q 12
 ip address 192.168.12.1 255.255.255.0
!
interface Ethernet0/1
 no ip address
 shutdown
!
interface Ethernet0/2
 no ip address
 shutdown
!
interface Ethernet0/3
 no ip address
 shutdown
!
interface Ethernet1/0
 no ip address
 shutdown
!
interface Ethernet1/1
 no ip address
 shutdown
!
interface Ethernet1/2
 no ip address
 shutdown
!
interface Ethernet1/3
 no ip address
 shutdown
!
interface Serial2/0
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial2/1
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial2/2
 no ip address
 shutdown
 serial restart-delay 0
!
interface Serial2/3
 no ip 

Open in new window

0

Switches / Hubs

21K

Solutions

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.