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 ...
- 19.5k
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 ...
- 98.8k
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 ...
- 98.8k
6
votes
Accepted
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. ...
- 19.5k
6
votes
Accepted
I can't ping the other router using OSPF protocol, Why?
(I imagine your setup to be something like this)
Your OSPF adjacency is not coming up because the IP addresses on the facing interfaces between R1 and R2 are not in the same subnet.
As soon as you ...
- 311
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 ...
- 8,826
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 ...
- 82.7k
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 ...
- 9,421
5
votes
Accepted
How come my gateway have different subnet ip
The subnet mask is 255.255.240.0 which means 20 bits belong to Network and remaining 12 is for host. The range of IP Address inside the network can be found by running your IP address against Subnet ...
- 197
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, ...
- 82.7k
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 ...
- 67.1k
4
votes
Accepted
Manual setting MTU still needed today?
Path MTU Discovery works by sending packets of various sizes to a target with the DF (Don't Fragment" bit turned on. If a router in the path has a smaller MTU, its behavior should be to send back an ...
- 15k
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 ...
- 9,421
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
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 ...
- 67.1k
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 ...
- 67.1k
3
votes
Accepted
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 ...
- 98.8k
3
votes
Accepted
Change device - Reassign static IP
You'd need to know the MAC address of the newly plugged in printer beforehand. Then you could reserve a specific IP address for that MAC address through DHCP Reservation.
Note that that's not the ...
- 264
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
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 ...
- 19.5k
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.
- 19.5k
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 ...
- 82.7k
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 ...
- 8,826
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 ...
- 67.1k
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 ...
- 2,346
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 ...
- 98.8k
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
Accepted
trace route result same hop but different destination ip
The reason for that result on a trace is that, some ISP, does load balance in his Autonomus System, thats it: same destination across diferent ways.
This is the reason that you looks, in the same ...
- 2,105
2
votes
How come my gateway have different subnet ip
That is because you are on the same network, 192.168.0.0/20. That network goes from 192.168.0.0 to 192.168.15.255. The network has 4096 addresses, and 4094 of them can be used for hosts.
- 98.8k
Only top scored, non community-wiki answers of a minimum length are eligible