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5 votes
Accepted

Is there a network cable tester device that tests the cables with realistic frequency instead of on/off leds?

What you're looking for is a cable tester able to certify a cable with the entire test suite. The tests must include crosstalk and detailed frequency measurement. Basically, there are three classes of ...
Zac67's user avatar
  • 84.9k
4 votes

Feeding a PoE capable device with variable power supply over TIA568 A cable (DC spares)

The PSE decides on which pairs power is supplied. A compliant PD needs to be able to use either pairs. Connecting a power supply to the spare pairs (only possible with 10BASE-T and 100BASE-TX) is not ...
Zac67's user avatar
  • 84.9k
4 votes

What are the most common scenarios in which the 'loopback interface' on a router is used?

A loopback interface is a virtual (i.e. not physical) interface that never goes down, unless you disable it. This way, if you configure an IP on this loopback interface and add it to your OSPF area (...
Benjamin A.'s user avatar
  • 1,697
4 votes

What are the most common scenarios in which the 'loopback interface' on a router is used?

...we learned that every router has a LOOPBACK interface. That is not true. Cisco routers can be configured with loopback interfaces, but they don't have loopback interfaces until you create one. ...
Ron Maupin's user avatar
  • 99.8k
3 votes
Accepted

What does "inline" mean in the context of cable testing?

“Inline” refers to PoE, not to the position of the tester. So this with this tester you can check cables doing power over Ethernet. You would still place the tester at the ends of the cable.
Teun Vink's user avatar
  • 17.4k
3 votes
Accepted

Iperf results on UDP Bandwidth

There is one particularity about iperf 2.0.x with UDP: Within the limits (CPU, NIC, UDP/IP stack and its buffers) of the sending system, iPerf will send traffic at the payload rate you specify with ...
Marc 'netztier' Luethi's user avatar
3 votes
Accepted

What binary prefix, JEDEC or IEC, is used for calculating networking gear speed

EDITED Despite the extended usage of binary in computer world and power of two based units (Byte, 32-bits word etc...), network bandwidth is commonly expressed in power of ten units. So it is (...
JFL's user avatar
  • 19.7k
2 votes

How to test if an sfp is working on juniper qfx5100

Check the manual/datasheets - both the switch and the transceiver should state what they're compatible with. If you're using a range of different optics it makes a lot of sense to maintain a ...
Zac67's user avatar
  • 84.9k
2 votes

WiFi TCP iperf throughput: upstream vs down stream

While passing downlink traffic (from the Access Point (AP)) to client-nodes, the AP schedules the packets from the packet-queues in the appropriate way and also does not face any contention on the ...
gpat's user avatar
  • 56
2 votes

iperf3 UDP tuning

That's how iperf3.x works. The "client" wants to establish a control channel to the "server" before any UDP transfer is started. That's why you can observe some TCP before the UDP ...
Marc 'netztier' Luethi's user avatar
2 votes
Accepted

How to use IXIA IxNetwork 8.40 to send bi-directional traffic between CPE and router

It took about 10 seconds to search the Internet to find this: To configure NAT translation in regular testing, all you have to do is open “Network Neighbourhood,”(In case you need a quick recap ...
Ron Maupin's user avatar
  • 99.8k
2 votes
Accepted

Confused about the results from the cable tester

I offer another interpretation: 4 wire cable for 100Mbit/s. This is basically the same as zac67's answer "Either it's a bad LSA contact, a bad panel insert or a damaged cable.", but probably the ...
Marc 'netztier' Luethi's user avatar
2 votes

Confused about the results from the cable tester

A cable tester of that type injects a pulse into the cable and analyzes the time it takes to reflect back. That tester can't really test/certify a cable deployment (you'd need attenuation, NEXT/FEXT, ....
Zac67's user avatar
  • 84.9k
1 vote

Using a switch and a pc to test the ports of another switch that resides in a device I wish to test

I need to verify the operation and signal integrity of the ports on the Device. You can verify operation with a simple software test but you can't verify (analog) signal integrity without special ...
Zac67's user avatar
  • 84.9k
1 vote

Iperf testing- Slow transfer speeds

In my experience Azure throttle the traffic and you can only achieve limited performance on a single flow. This is because aside the public access they sell the express route circuit. If you could ...
JFL's user avatar
  • 19.7k
1 vote

IPerf test| Server side Sender data shows that the bandwidth is zero but Client has bandwidth of 125 Mbps

With iPerf3 [1], looking at, respectively working from the responder or "server" side (running iperf3 -s) is of lesser interest. You can gain as much, or even more information from the ...
Marc 'netztier' Luethi's user avatar
1 vote
Accepted

Cat5 Ethernet cable between buildings passes connectivity test but switch light not lighting up and no connectivity

Very often when a cable suddenly fails, the termination isn't good enough. Double check each side's termination, and if that doesn't help replace the cable. If you haven't done so, make sure no small ...
Zac67's user avatar
  • 84.9k
1 vote
Accepted

How to test the maximum of clients connected to an AP?

From what I know there are no upper limits in the 802.11 protocol. There are software limits in some of the AP's I've worked with. Aerohive usually have 100 concurrent stations on most AP's. The way ...
OlofL's user avatar
  • 108
1 vote

How to duplicate multicast source over several multicast addresses

A multicast group is a destination IP address on an IP packet. The destination IP address is determined by the sender, and modifying an IP address on a packet is called NAT (Network Address ...
Ron Maupin's user avatar
  • 99.8k
1 vote
Accepted

How to test outoing traffic on random ports? (on OS X)

Use a program like NMAP to determine what ports are open to what addresses. Security operations(assuming your network has a security team) may not appreciate this as it will look suspicious when you ...
Skiltvakt's user avatar
1 vote

Simulate a proxy or server that is silently dropping pooled tcp connections?

You could put in a router with NAT or a firewall between, and set the TCP timeout to be very low. Alternatively, you could try to correct the situation by using TCP keepalive. This will periodically ...
Ron Maupin's user avatar
  • 99.8k

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