Questions tagged [cisco-catalyst]

A tag for questions related to Cisco's Catalyst line of switches.

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48
votes
24answers
95k views

How can I see which switchports are not in use?

On a large Cisco Catalyst switch stack, almost all switchports are patched. I need to identify the ports, which are not in use, for connecting further devices. Following switchports, cabling, patch ...
24
votes
10answers
272k views

How to find the port a device is connected to, based on IP, on a Cisco Catalyst switch

On a Cisco Catalyst switch, I need to find what port an end device is connected to. I have the IP address/host name. How do I quickly find the port?
24
votes
5answers
27k views

Accidentally Removed Allowed VLANs from Cisco Switch Dot1Q Trunk

I am adding a new VLAN to an existing trunk port between two Cisco Catalyst switches (3750's). In the process of adding the new VLAN, it appears that I've removed the existing allowed VLANs on the ...
23
votes
4answers
9k views

Can I use a Catalyst 2960-S for iSCSI?

I need to set up a modest iSCSI SAN with a few ESX hosts and one storage array. Can I get by using a Catalyst 2960-S or do I need to upgrade? Are there any special tweaks I need to make to the switch ...
21
votes
4answers
20k views

Troubleshooting “Down BGP” connections

Our network experienced a short outage when one of our BGP routes went down for a short time yesterday. Thankfully our connections failed over to our secondary BGP route after a few minutes, and the ...
19
votes
3answers
4k views

What is the difference between all the switching modes on 6500/7600?

On one of my routers, I see the following switching modes: #show fabric switching-mode Global switching mode is Truncated dCEF mode is not enforced for system to operate Fabric module is not ...
16
votes
5answers
74k 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 ...
15
votes
3answers
6k views

Configure Cisco ASA in Transparent mode: Layer2 DMZ w/ Vlan translation

I am in the middle of a project to migrate some existing switched ethernet dot1q trunks behind an ASA firewall... these trunks have five vlans each (numbered 51 - 55). This is a simple drawing of the ...
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
2answers
9k views

ASICs vs x86 general-purpose routing/switching

SysAdmins often try to convince me that x86 general-purpose OS's can perform just as well as routers with low MHz CPUs and dedicated silicon (i.e., ASICs) at 1Gbps line rates. This thinking is ...
13
votes
2answers
22k views

How can I verify QoS DSCP marking on a Cisco Catalyst 4500E?

Good afternoon, I've got a shiny new 4500E running 15.0(1r)SG7 that is set to replace an ailing 3750E. It is running ipbase for now. On the 3750 I was able to check out the incoming DSCP/CoS values ...
12
votes
8answers
6k views

How do you convince management that 3560/3750s are a bad idea in your DC?

3560/3750s have small buffers and make good wiring closet switches. However I very often see these switches sitting in DCs. Lots of folks tend to use them as they are generally 1Gb and L3 capable. Is ...
12
votes
1answer
6k views

Translating SNMPWALK output into human-readable format

I am asking this question which is related to a question I previously asked and was comprehensively answered by @MikePennington. When I asked that question, I intended to know how to poll arp table ...
11
votes
3answers
6k views

What are the alternatives to OTV for stretching a layer 2 network across 2 datacenters?

We want to find a "safe" way to stretch layer 2 network across 2 data-centers, and since we don't have any equipment running NX-OS on either data-centers we can't use OTV. So what are the alternatives ...
11
votes
2answers
4k views

catalyst 3750x - jumbo frames on svi

I've encountered a problem on a cisco ws-c3750x-48ts-s where jumbo-frames won't cross a trunk-connection between a vwmare esx-host and the switch. The access ports in the same vlan don't experience ...
11
votes
1answer
2k views

Cisco Catalyst 3750/3560 SYN FLOOD protection

How could one mitigate SYN FLOOD DOS on Catalyst 3750/3560 as it has no control plane protection?
11
votes
2answers
1k views

How did I break (half of) my network?

I'm looking for some post-event advice so this event doesn't happen again. We have a network core of two Cisco 4500x switches, configured for VSS redundancy. From those, we have iSCSI devices, our ...
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-...
10
votes
2answers
4k views

KEMP load balancers using UCARP (VRRP) - multicast MAC address not being picked up

Alright - been battling this for at least 20 hours consecutive.. Sorry if this seems like a long rant, or a blog post, but I'm getting to the point of exhaustion. So, here's the deal. We're using ...
10
votes
2answers
5k views

How to infer 2960S switch base ethernet MAC Address

Cisco switches seem to allocate unique MAC address for each interface they have, this includes ports and vlan interfaces. These unique MAC are derived from a "Base ethernet MAC Address", which can ...
10
votes
4answers
1k views

Strange 2960 behavior on my network

I have a bunch of Cisco routers and switches in our buildings. Basically, every building has one router and one or more switches. I use just two VLANs for each building: VLAN1 is the data VLAN (native ...
9
votes
4answers
3k views

Overcome 2 monitor session limitation in Cisco VSS

Is there a way to overcome Cisco's 2 monitor session limitation on a VSS 6500 without the use of a network tap?
9
votes
4answers
3k views

Switch interface config for IP Phones

I have seen both of the following methods of switch interface configuration for supporting IP Phones. switchport access vlan <data-vlan> switchport voice vlan <voice-vlan> switchport ...
9
votes
4answers
52k views

How to find a list of devices connected to my network (IP's and MACs)

I am trying to get a list of the devices that are connected to my Cisco (Catalyst 2960) switch. Preferably through SNMP. Here is what I've already done: I was able to retrieve the ARP table from the ...
9
votes
2answers
996 views

carrier's vlan tags overlap my own

I have a 3 site network: one is a data center colo and the other two are offices. The new Metro Ethernet service we just installed requires the colo site's traffic destined to the offices to be in ...
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/...
9
votes
1answer
8k views

Is 'switchport protected' supposed to block unicast flooding?

Does having switchport protected configured on an interface prevent unicast flooding for a MAC address the switch hasn't learned? The information that I'm seeing conflicts -- the wikipedia page on ...
9
votes
1answer
2k views

Problems Connecting Catalyst 2960G to Netgear Prosafe Via Fibre

I've got a catalyst 2960G, connected to a Netgear Prosafe GS718T switch (cheap manageable switch). Idea is I have a couple of users that need access to a test environment - hence the cheap switch. It'...
8
votes
3answers
4k views

Traffic Policing

I know traffic policing isn't something that you normally find in a LAN environment, and I wish I wouldn't be finding it in mine. That being said... I have no choice. The device is a 3750X. The ...
8
votes
5answers
7k views

Connecting two different Cisco Switches using Fibre

I have two Cisco Catalyst 2960-24TC-L switches and would like to connect them using fibre over a distance of 200Meters. According to cisco, the switches has two SFP ports, which I can clearly see on ...
8
votes
3answers
4k views

Using Fabric on a Cisco device : “Line has invalid autocommand”

I wasn't sure where to ask this but it seems to be something on the switch side so I thought I would start here first. I am working on a little project to automate updates to config files in bulk ...
8
votes
2answers
6k views

IGMP snooping and link-local multicast addresses

I have a network which has many devices sending data to 224.0.0.225 on a VLAN which spans multiple switches. Each device (aprox 12 of them) is sending reporting data at roughly 500-600 kbps. Each port ...
8
votes
4answers
13k views

802.1x on Access VLAN only, not on Voice VLAN

I've successfully configured a Cisco 3750G to perform the authenticator function of the 802.1x process. I have a test Win7 machine as a supplicant and a Windows 2008 server running NPS as the ...
8
votes
1answer
2k views

Catalyst 4500R+E, Sup7L-E Strange License Management

We have Catalyst 4500R+E with Sup7L-E (IOS XE 3.4SG). It was bundle with LAN Base License Installed. #show license summary Index 0 Feature: entservices Period left: 8 weeks 4 days ...
8
votes
1answer
2k views

Are the SFP/SFP+ int's on WS-X45-SUP7-E autosensing?

I have two Cisco Catalyst 4510R+E systems that I am interconnecting, using the interfaces on the sup's (both have dual Sup7-E's.) They are marked 1G/10G Uplinks (SFP/SFP+) on the sup above the ...
8
votes
1answer
395 views

IOS changes the SNMPv3 engineId

I have encountered a very strange problem when configuring remote target engineId on a Catalyst 3750 switch. The switch changes the engineId, it puts a zero between the two last digits. As shown below ...
8
votes
2answers
2k views

Basic Catalyst 3560 Egress Shaping

We have a service provider (and we can't change providers) who is giving us a "metro ethernet" style connection between two of our locations. On each end, we plug into an ethernet port on a provider's ...
8
votes
1answer
1k views

Native Vlan Cisco Catalyst and Layer 3 switch

I have run into an interesting issue setting the native VLAN between one of my Cisco Catalyst 2960 and my Layer 3 switch (third party). Here is the setup, the layer three switch is set up to run on ...
8
votes
1answer
43k views

SFP+ complains threshold violation and went down

All, Recently bought 3 Cisco switches: 3560x and two 2960Xs. 3560 acting as the core switch and other 2 switches are connected using SFP+ (One SFP-H10GB-CU1M and other SFP-10G-SR) I have issue with ...
8
votes
1answer
1k views

Private VLANs on a switch that doesn't support Private VLAN trunks

I have a Catalyst switch that doesn't support PVLAN trunks (Sup4, 4500, 12.2(54)S). I have multiple other Catalyst switches, 3750 metro, that do. Am I correct in assuming that because the C4500 does ...
7
votes
4answers
3k views

Cisco Catalyst 4500E - modules installation

I have the following questions on Catalyst 4500E hot-swappable hardware components; Is it possible to insert/pull out line cards to or from powered on chassis? Is it possible to insert redundant ...
7
votes
4answers
6k views

MAC Address table brings several different mac addresses for one port

i have a CAT2960 switch from which i am polling mac address tables the cable from the ethernet socket to the switch is placed in port 24, and i have 2 more pc ethernet cables in port 3 and port 7. ...
7
votes
2answers
2k views

Cisco 2960X is 'normal' IOS CLI or not?

I asked a previous question "Low end cisco switch with 'regular' CLI - which led me to look at the 2960X platform as an affordable access layer switch at a branch office.. I know on the older 2950's ...
7
votes
3answers
747 views

Can I run FCoE over Cisco Catalyst 5500?

I have 2 spare older Cisco Catalyst (not Nexus) 5500 switches. Would I need any additional hardware in order to run Fibre Channel over Ethernet (FCoE) over them? Do I need some kind of management ...
7
votes
1answer
4k views

CISCO 4500R+E, Sup7L-E redundancy: RPR or SSO?

We are going to deploy 4500R+E chassis with two redundant supervisors Sup7L-E. All ports in chassis - switchport with trunks. L3 interfaces - SVI. Chassis wll terminate L3 domain (route between zone),...
7
votes
3answers
3k views

ISR routers - difference between routed and switched ports

On a Cisco ISR router - would you say there are any benefits from purchasing an HWIC or EHWIC to connect to the next set of switches within the branch network? For instance. Lets say Gig0/0 and Gig0/...
7
votes
2answers
2k views

Cisco Catalyst cluster heartbeat switch issue - increasing input errors

PROBLEM: The servers in two clusters keep losing heartbeat connectivity with each other thus causing database outages. Outages are brief but disruptive. SETUP: There are two clusters of three ...
7
votes
2answers
3k views

Tacacs VRF authentication

We just got a new Supervisor7 with os 3.4.1. I'm trying to configure authentication with tacacs, and I can't understand how to make it work. This configuration works on our other switches, but it ...
7
votes
4answers
9k views

SCP lost connection

Occasionally I have an issue when I try to SCP a file to one of our Cisco devices. When the connection starts, it immediately drops and says "lost connection". I've had this happen when there wasn't ...
7
votes
1answer
374 views

In 802.1Q Tunneling what exactly is meant by “a point-to-point topology before you enable tunneling for PAgP, LACP, or UDLD”

I have one switch that I want to use as an 802.1q tunnel, to make the spanning tree and etherchannel transparent, a pass through switch between a core switch and access closets, because I do not have ...

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