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 ...
- 19.8k
7
votes
Accepted
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 ...
- 101k
7
votes
Accepted
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 ...
- 101k
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 ...
- 8,896
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 ...
- 88.1k
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 ...
- 9,565
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, ...
- 88.1k
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 ...
- 68.1k
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 ...
- 68.1k
4
votes
Accepted
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 ...
- 333
4
votes
Accepted
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 ...
- 68.1k
3
votes
Accepted
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.
- 19.8k
3
votes
Accepted
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 ...
- 19.8k
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"
- 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 ...
- 88.1k
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 ...
- 8,896
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 ...
- 68.1k
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 ...
- 2,356
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 ...
- 101k
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
- 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 ...
- 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 ...
- 19.8k
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 "...
- 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 ...
- 88.1k
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 ...
- 88.1k
2
votes
Connecting internal network to public server
There are 2 approaches for VPN, one is site-to-site VPN and other is VPN client access. I think VPN client access is sufficient(If the hosted app server is the only server wants to access 172.16.1.0/...
- 461
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 ...
- 121
2
votes
Why traceroute is still Used?
People use it because it is available everywhere and it works fine on simple networks. Yes it falls down in some complex networking scenarios and yes those running those complex networks need advanced ...
- 13.8k
2
votes
Accepted
How can IPv6 host know default router's IPv6 address using RA?
The RA IPv6 packet will have the router address as the source IPv6 address.
A host doesn't really need to know the router's IP address to send packets to other hosts. On a LAN, frames are sent to a ...
- 101k
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