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1500 questions
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10 answers

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?
Brett Lykins
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4 answers

Does physical distance affect download speed?

I just had an argument with a colleague of mine and thought I'd just reach out to the experts on this. Here's the scenario. We were using a website that measures your connection's speed. We tested using a server that is far from us (We are in…
Navid
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1 answer

Should IPv4 ICMP from untrusted interfaces be blocked?

Searching around I haven't been able to determine the best practice for ICMP on a firewall. For example on a Cisco ASA would it be safe and recommended to allow ICMP from any if ICMP inspection is enabled. This would then allow for things like type…
Adam
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25
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5 answers

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 trunk... How is this possible? Existing trunk port…
Brett Lykins
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24
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1 answer

What is the practical use of a /31 CIDR or 255.255.255.254?

With a /31 subnet, we are left with zero usable hosts. The /31 subnet only has two hosts - one for network and another for broadcast. I am wondering why would someone ever use this subnet.
Bali Vinayak
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24
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3 answers

Why is broadcast used at the DHCPREQUEST step?

This is the process of DHCP operation, My question is at the 3rd step why does the Client send a Broadcast and not a Unicast as after the previous two operations the address of the DHCP server / Relay server should be known?
arif
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24
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7 answers

Why use iBGP inside an Autonomous System, if IGP protocols fulfill the need for internal communication

Can anyone explain why we need iBGP for the routes when we have the IGP protocols (OSPF, RIP) for internal communication within the AS? I have read a lot of articles and books, but I could not find the answer.
user2720323
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24
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2 answers

Emulate Ethernet frame loss for testing purposes

Maybe I am missing something rather basic, but I don't know so I figured I would ask. In terms of testing, how sensitive various TDMoE are to BER and packet delay, I am looking into how to simulate delay and random packet dropping at the ethernet…
Chris Travers
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24
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8 answers

How can I force VTP clients to update their VLAN database from the VTP server, on Cisco devices?

I was doing some cisco exercises on configuring a vtp server and client, something I can't figure out is : I setup a vtp server, added my VLAN's I then took another switch that was attached to this vtp server and set it to client Now my VTP client…
Lucas Kauffman
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24
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4 answers

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 in order to handle iSCSI? The switch will be…
Jeremy Stretch
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24
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4 answers

What is the difference between netFlow and sFlow?

How is sFlow different from netFlow, and how is each supported by different vendors ?
Benjamin A.
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23
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7 answers

Difference between access list and prefix list?

Can someone explain with an example whats the difference between an access list and prefix list.
NAVEEN GEORGE
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23
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7 answers

Minimum Ethernet Cable Length?

I have heard from a few people that cables less than 1 meter are prone to transmission problems. Is there any minimum copper cabling length? Please explain if this is true or not and share any available RFCs or standard documents. Thanks.
Jim
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23
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4 answers

NACK vs. ACK? When to use one over the other one?

Personally I don't even feel that there is a need for ACK. It's faster if we just send NACK(n) for the lost packets instead of sending an ACK for each received packet. So when/which situations would one use ACK over NACK and viceversa?
nFu9DT
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3 answers

What is "industrial ethernet"?

When a teacher introduced it to us he gave the impression that it specifically covers some Siemens technology; that it's even a Siemens trademark. I believe the term covers something more general, but I haven't been able to find a useful definition…
Mads Skjern
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