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9 votes
Accepted

Why traceroute is still Used?

Traceroute doesn't give inexact information, it performs tests in a specific way and give some results based on the response it receives (or do not receive). You have to know how to interpret the ...
JFL's user avatar
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7 votes
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What are the key advantages and disadvantages of NDP compared to ARP?

As Michael Hampton points out, ND does a great deal more than IPv4 ARP, but I will answer from the perspective of simply resolving a layer-2 address from a layer-3 address (ARP function). ARP ...
Ron Maupin's user avatar
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7 votes
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Is this computer a threat? On same network range, but in a workgroup

The situation you describe is very similar to what cost Target* many millions of dollars when its network was hacked, and customer information was stolen. Never let another company have something ...
Ron Maupin's user avatar
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6 votes
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What is persistent connection and session

First a word about: I understand word persistent as following : no one else can occupy wire at the time of persistent connection. So this connection is only one-to-one. But this is not right. ...
JFL's user avatar
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6 votes

Cant ping & access HP switch on network connected on trunking mode

(Disclaimer: I am not familiar with HP switches, so I wont' be able to give proper command syntax for show/display commands). For a first, let's leave all routing discussion aside. AS5500 an AS3100 ...
Marc 'netztier' Luethi's user avatar
6 votes
Accepted

Understanding how devices on a LAN/VLAN discover the existence of other local devices

This is an actual problem. Most often, one hosts "wants" something from the other host, so it'll try to connect via a known DNS name. In a company network, a DNS server provides the IP address for a ...
Zac67's user avatar
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6 votes

Juniper SRX answers all ping requests instead of forwarding

The session output shows that the box is translating the destination address 10.5.5.22 to 10.41.22.3 and then routing it out ae0.22 instead of ae0.5 like you'd expect. It is very likely that your NAT ...
Benjamin Dale's user avatar
5 votes

How does a host know the ip addresses of other hosts on the same LAN?

But ARP seem to take an ip address as input and give the corresponding MAC address. That is correct (for IPv4). ARP can also be used to check if an IP address is already in use (for DHCP, Zeroconf, ...
Zac67's user avatar
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5 votes

How does a host know the ip addresses of other hosts on the same LAN?

But say two hosts are connect in a LAN, how does host A know that B exist and that B has the ip address, say, 192.168.0.6? Simply put, the application tells it so, either by specifying the address or ...
Ron Trunk's user avatar
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4 votes
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Cant ping & access HP switch on network connected on trunking mode

You should check the portal server limitations, since it is enabled on A5500 Vlan 1 interface: # interface Vlan-interface1 ip address 172.16.1.1 255.255.255.0 portal server 1 method layer3 # While ...
Marco De Lellis's user avatar
4 votes
Accepted

How would I track down what port a device is on remotely?

This is exactly the process I would use in most circumstances. If you have CDP (Cisco Discovery Protocol) enabled on all your switches though, you can save a LOT of time by running Cisco's MAC ...
Benjamin Dale's user avatar
4 votes

Given a network switch, can we identify the devices (IP not assigned yet) connected to it?

If you can get the server to generate some traffic, you can determine the manufacturer of the NIC card from the OUI portion of the MAC address. That isn't the same as the server manufacturer, but ...
Ron Trunk's user avatar
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4 votes
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Network topology discovery with Flows

The problem with looking at flows is that you only see the source and destination, and nothing in between. Also, you only see flows that exist at the time you capture data. There may be other ...
Ron Trunk's user avatar
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3 votes
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Find all printer on the network

Most of (any?) network printers can be joined on TCP port 9100, so you can use NMAP (or other suitable software) to scan for all hosts with this port opened on all your networks.
JFL's user avatar
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3 votes
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tracert command return Request timed out

Extract from Microsoft Support How to Use TRACERT to Troubleshoot TCP/IP Problems in Windows The TRACERT diagnostic utility determines the route to a destination by sending Internet Control ...
JFL's user avatar
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3 votes
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What happen underneath when I manually change my IP address?

Wouldn't there be a chance that two people under the same subnet enter the same IP address and they go into confict? How to prevent them ? Yes, that can, and does, happen when networks have manually ...
Ron Maupin's user avatar
  • 100k
3 votes

Pinging broadcast address

FOR /L %i IN (1,1,254) DO ping.exe -n 1 -w 500 192.168.1.%i | FIND /i "Reply"
Steve's user avatar
  • 31
3 votes

GHOST servers or devices in Vulnerability scan report

We can't help you with your management tool. However, you can track down an unknown IP address in your network by examining the ARP tables of connecting devices, routers, ... and looking for the ...
Zac67's user avatar
  • 85.7k
3 votes

Understanding how devices on a LAN/VLAN discover the existence of other local devices

One possible way (by far not the only one) is mDNS based Service Discovery as per Zeroconf Networking, based on link-local multicast (see Zac67's statement) and the DNS domain .local. For a good ...
Marc 'netztier' Luethi's user avatar
3 votes

How to detect passive network host?

You can slow Nmap's discovery way down, so it won't disturb fragile equipment. First do a simple ping sweep. You can go very slow, taking hours (or days) if need be. Once you know the active ...
Ron Trunk's user avatar
  • 67.8k
3 votes
Accepted

How my neighbour machines in the same network knows my interface ip?

Simple answer: The machines don't know the route. The IP address that you use must be in the range of the so-called "subnet" the machine belongs to. This means that all machines that can be reached ...
Martin Rosenau's user avatar
3 votes
Accepted

Does Network Discovery (rfc2461) preclude ARP sniffing?

Does Network Discovery (rfc2461) preclude ARP sniffing? No, IPv6 prevents ARP sniffing. IPv6 does not use ARP, which requires broadcast, and IPv6 does not have broadcast. Instead, IPv6 makes heavy ...
Ron Maupin's user avatar
  • 100k
2 votes

Pinging broadcast address

Try this on all the machines of your network to receive packets from them when pinging the broadcast address sudo sysctl net.ipv4.icmp_echo_ignore_broadcasts=0
Fuji San's user avatar
  • 121
2 votes

Pinging broadcast address

Many modern OS have disabled responding to the broadcast. They ignore them to avoid security issues. If you use Linux, check your settings with: sysctl net.ipv4.icmp_echo_ignore_broadcasts If it ...
JS-Ng's user avatar
  • 21
2 votes

How can I discover Apple TV's on my network?

Apple Bonjour protocol use Multicast DNS, which has been normalized in RFC6762 and RFC6763. It uses multicast IPv4 address 224.0.0.251 or IPv6 address FF02::FB An bonjour enabled device will announce ...
JFL's user avatar
  • 19.7k
2 votes

How does equipment know it has devices connected to it?

Basically, for "knowing that something have been plugged in", there is a specific mechanism on the physical layer called "link pulse" These link pulses are (now) included in the whole "...
Golgot's user avatar
  • 427
2 votes
Accepted

How does equipment know it has devices connected to it?

It's called Autonegotiation: Wikipedia Ports looking for a link send "link pulses" on the data lines that (mostly) convey speed(s) and half/full duplex capabilities. When both sides agree on common ...
Zac67's user avatar
  • 85.7k
2 votes

how to discover devices in a large heterogenous network with huawei, cisco, alcatel and more different devices without using snmp?

It depends on what layer you want to/can discover devices. At the link layer, LLDP comes to mind but it requires you to directly interface with the device and only gives just a few items. In a layer ...
Zac67's user avatar
  • 85.7k
2 votes

Cant ping & access HP switch on network connected on trunking mode

Your switch on the right (A3100) doesn't have a default gateway nor a route toward other subnets to answer back. It can only talk to machines within the subnet 172.16.1.0/24. If you send the ping ...
Tensibai's user avatar
  • 121

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