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Questions tagged [switch]

For questions about network switches, the term commonly refers to a multi-port network bridge that processes and routes data at the data link layer (layer 2) of the OSI model.

17
votes
7answers
50k views

Cisco command to show which interfaces an ACL is applied to

For Cisco routers and switches, is there a show command, or something similar, that will display what physical and logical interfaces an ACL is implemented on and what direction it is applied in? I ...
2
votes
4answers
22k views

Ethernet device works on certain ports on Ethernet switch but not on others

I have a small and inexpensive ethernet switch which is giving me some headache. For some reason some devices only work when I plug them into specific ports. The ports are not broken, as other devices ...
8
votes
2answers
1k views

Switch-Assisted Load Balancing w/ Fault Tolerance

While studying for Cisco and Microsoft certifications I read a lot about NIC Teaming, Etherchannels and similar stuff. I know you can do static teaming in MS Windows Server or creating a port-...
18
votes
1answer
3k views

Finding transparent firewall packet loss

We use the Cisco ASA 5585 in a layer2 transparent mode. The configuration is just two 10GE links between our business partner dmz and our inside network. A simple map looks like this. 10.4.2.9/30 ...
6
votes
1answer
652 views

Passing Traffic through Traffic Management Device in transparent mode

We would like to pass traffic tagged (in the same vlan) from Router_1 to Router_2 throught a Traffic Management device (in transparent mode). Now, we are using two switches (running and aimed config ...
7
votes
3answers
13k views

Flow Control: to be or not to be?

We deploy two 3750-X switches in stack and connect Dell Storage to 10G-T ports. Dell recommends to use flow control on this ports, but some people have a lot of problems with this feature (packet loss,...
5
votes
6answers
2k views

Monitoring Network Traffic

I currently make use of a NETGEAR FVS338 firewall and a NETGEAR 24 port switch. Is there a way to graphically or in some way monitor their traffic? Edit: Switch Model FS726T
4
votes
1answer
2k views

CRC & Align Errors on D-Link switch, network down

I have network topology: (room 3) D-Link DES-1024D | | (room 2 MAIN) (room 4) Baseline 3COM Switch 2948-...
9
votes
3answers
3k views

Trying to test a virtual lab VRRP configuration for STP issues

I'm in the middle of setting up a lab with a VRRP configuration, and I'm trying to search for any possible issues we might run into in production. One issue I am aware of with VRRP is that it seems ...
14
votes
3answers
39k views

How to Monitor Vlan Traffic?

We have migrated to a new ISP who provide us several services (Internet+VoIP+VoD) and have divided each service in one vlan 100,101,102 respectively. Now I'm looking for a solution to monitor each ...
8
votes
1answer
2k views

Switch replacement procedure 3560G to 3750X

My company will upgrade two Cisco 3560G switches (an HSRP Active & Standby pair) to two Cisco 3750X switches in a stack. I need to make a switch replacement procedure starting from removal of the ...
5
votes
2answers
3k views

riverbed wan optimizer does not receive traffic

I have 2 Riverbed WAN optimizers and a WAN simulator. I connected 2 WAN ports of the 2 Riverbeds to the WAN simulator, connected 2 LAN ports along with 2 servers on a switch, and configured 2 subnets ...
6
votes
2answers
2k views

Cisco 7609-S Line card error counter is regularly exceeding threshold

I am receiving the following syslog messages on a 7609-S. Jun 17 11:52:27.560 BST: %CONST_DIAG-SP-4-ERROR_COUNTER_DATA: ID:47 IN:4 PO:255 RE:169 RM:255 DV:5 EG:2 CF:10 TF:472 Jun 17 11:52:27.560 BST: ...
6
votes
1answer
2k views

WS-X45-SUP6-E / WS-X45-SUP7-E compatibility w/4510R (non-E)

The EOL announcement for the Cisco WS-X4516 on a 4510R (non-E series chassis) states that the WS-X45-SUP6-E is a replacement though this SUP is for the E-series chassis. Incidentially, the SUP6 is ...
5
votes
2answers
3k views

Fortigate HA: how to locate switch port connected to passive unit?

In a new customer's network I have found the following scenario: Fortigate 1 and 2 form and HA cluster in active-passive mode. The HA link is just a cable connecting them directly. Racks A and B are ...
10
votes
4answers
5k views

Redundancy between router and servers

In the past, I was using a NetGear GS724T between my router and my servers. Unfortunatly the switch suddenly died. Now I've changed it for a GS748T and also bought one more and I am wondering how I ...
5
votes
3answers
3k views

Is a router always necessary to link two subnets?

I am thinking especially of VLANs, which represent separate subnets that may need only one switch.
10
votes
4answers
16k views

Setting up DHCP server on the router or on the switch?

We're using the Cisco 1921/K9 with a SG300 L3 switch. Does one set up DHCP server on the router or on the SG300? If both is capable, what is the reason to choose one over the other? Note: I have 4 ...
11
votes
11answers
3k views

Locate a host on Network

What is the best method of locating a particular workstation on a VLAN ? I sometimes need to do this, if a workstation IP address, shows up on an ACL Deny torrent use High bandwidth usage (Top ...
11
votes
1answer
5k views

Cisco IOS built-in SSH client default version

You issue the command ssh 192.168.97.97 from a IOS device and the destination IOS router/switch SSH server is accepting both SSH versions. Being that you did not specify a version to use on the SSH ...
14
votes
4answers
4k views

What happens when 2 computers transmits at the same time to a 3rd one in a full duplex switch?

Consider the following scenario: I have 2 PC's (PC1 and PC2) that wants to transmit at the same time to PC3 in a full duplex ethernet switch. Let's consider that all ports are in the same VLAN, so ...
14
votes
3answers
3k views

Why we get high fluctuation on bandwidth measurement Cacti graph?

We were on redundancy test of Etherchannel and Routing on our network. During this intervention we made some measurement. Our monitoring tool is Cacti for graph. The equipment monitored is a 4500-X ...
12
votes
5answers
2k views

Do faster segments of a network mean faster flow rate or lower latency?

This is another one of those hypothetical questions. I've been trying to figure out whether or not having a faster 'segment' of a network in between host A and host B will translate into a faster flow ...
9
votes
2answers
608 views

CDP not available to be enabled on ME3400 port

We have a ME3400 that we want to enable CDP on but there is no cdp option. Why is it not available? switch(config)#int gi0/1 switch(config-if)#cdp ? % Unrecognized command CDP is enabled globally. ...
10
votes
3answers
2k views

DHCP assign IP address based on MAC address with Cisco CE 500 platform?

I have very little knowledge about CISCO and its switches, but now I have to configure it myself. Is it possible to allot IP address based on MAC address on CISCO CE 500 (Cisco Catalyst Express 500-...
4
votes
4answers
1k views

Can a VLAN bridge be used to replace a bypass switch with an IPS device?

I am wondering if it's possible to set up a way to remove the need for a bypass switch when using an IPS device. To summarize, I would have an IPS device acting as a virtual wire on a connection I'm ...
21
votes
7answers
7k views

Building new network and need 200+ wireless devices

I'm planning the network for my company's new office space. I'm not an expert so I'd like to present my plan and ask y'all nice folk to tell me if and where I'm making mistakes. Assumptions: Office ...
5
votes
3answers
878 views

Is it necessary to use layer 2 switches with microwave point-to-point links?

For a university project we are designing a network across 3 buildings for a small business. I've decided to implement a microwave point-to-point to connect each building. A lot of microwave point-to-...
4
votes
2answers
4k views

Brocade switches per vlan STP support

Do Brocade switches(FastIron, NetIron, ICX, etc) support using a per vlan spanning tree or do they only support a single spanning tree instance for all VLANs? If they support per vlan: Is it ...
7
votes
5answers
13k views

How to test layer 2 connectivity on Cisco Switch?

I'm testing a new FTTH CPE in our lab. A Cisco ME3400 switch. So far I'm having issues in provisioning them. I have activated DHCP debugging to see the DHCP packets. I wonder how can I test to know ...
9
votes
2answers
3k views

3750G Switch Buffer Monitoring

We have put some 3750Gs in a stack for our DC access switches. We are concerned that these won't be able to handler higher data loads as traffic increases due to their limited buffers. What statistic/...
19
votes
5answers
17k views

Should portfast be used on a port potentially connecting to an unmanaged switch?

I understand the basics of how spanning tree works and why you would want to use portfast on user access ports. When dealing with a topology with a large number of dumb switches under desks and ...
6
votes
4answers
347 views

Cisco SFP module: Determing Priority?

I have two 3750 Cisco switches that have two fiber cables/sfp modules hooked up on each. The second fiber is just for redundancy. I have installed two new 3750X switches on the rack for the upgrade, ...
18
votes
3answers
26k views

How do you know if a Cisco switch is handling traffic well?

I have just read Jeremy's question about 2960-S and iSCSI traffic handling, which drove me to ask this question: We all have lots of switches deployed in distinct infrastructures, how can you know ...
16
votes
8answers
17k views

When *not* to create a SVI for a L2 VLAN?

When creating VLANs for just L2 on a switch -- routing will be handled by a device within that VLAN such as a load-balancer -- it isn't necessary to create the vlan interface. As a matter of habit, I ...
14
votes
2answers
11k views

Why does “show interface” show “Last input never” when packets input is incrementing?

Why is it that when I perform a show interface command I see that Last input always shows never? FastEthernet1/31 is up, line protocol is up (connected) Hardware is C6k 100Mb 802.3, address is 000d....
14
votes
7answers
8k views

How to connect 5 different networks together?

I have a network consisting of three servers in a data center, all of which are connected to each other via a switch. In addition to this I need this network to access 4 additional networks, most of ...
6
votes
4answers
4k views

Are multiple links with different VLANs between two switches possible?

I'm not considering Etherchannel or LACP. Given 2 Ethernet switches A and B, where both switches have port 0 configured as a tagged trunk for VLAN 100 and 101 and port 1 configured as a tagged trunk ...
11
votes
3answers
2k views

Is there such thing as a network bridge?

Is there such a thing as a network bridge or is it always meant as a switch implementing a bridging function? Whilst bridges are described as devices that create separate collision domains in network ...
42
votes
15answers
76k views

How can I diagnose a bridging (ethernet) loop?

Given that spanning tree has failed (or you don't have any spanning tree) and get an ethernet loop, what's the best way to diagnose where the problem is? Which switch?, which cable? and so on.
15
votes
4answers
1k views

Is Nexus 7000 series line card “OIR” impact-free?

I have read many data sheets on the Nexus 7000 series and it's cards purporting to be capable of OIR (Online Insertion and Removal). However I have never needed to replace/reseat/add any Nexus line ...
8
votes
1answer
1k views

Migrating from STP short mode to long mode?

It was decided recently to migrate a large campus network from the short mode STP costs (16-bit) to the long mode STP costs (32-bit). I have clearly found it documented that this needs to be a "...
14
votes
5answers
69k views

What causes total output drops on a cisco switch interface?

I have an HP c7000 blade chassis which contains Cisco 3120X and Cisco 3120G switches running ios 12.2(58)SE1. The blades themselves are very lightly loaded yet many interfaces on different blade ...
14
votes
5answers
677 views

In a multi-tenant environment what should be done to make your switchports silent on Cisco and Juniper switches?

For example preventing it from sending arp, stp, etc and to reveal as little as possible about the rest of the network. Example use case would be connecting to a peering exchange.