Questions tagged [networking]

For questions about networking in general. Any question about all on topic network devices can use this tag.

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26
votes
7answers
12k views

Why does DHCP use UDP and not TCP?

DHCP uses UDP as its transport protocol. DHCP messages that a client sends to a server are sent to well-known port 67 (UDP—Bootstrap Protocol and DHCP). DHCP Messages  that a server sends to a client ...
24
votes
7answers
9k views

Why can I traceroute to this IP address, but not ping?

I have an IP address and can traceroute to it, but I can not ping. You see, I can traceroute 43.24.226.50: dele-MBP:~ ll$ traceroute 43.24.226.50 traceroute to 43.24.226.50 (43.24.226.50), 64 hops ...
13
votes
3answers
2k views

What is the least possible separation of two NICs with the same MAC address?

Suppose you have two NICs with the same MAC address, but not necessarily the same IP address. What is the least possible separation (in terms of number of switches, routers, different IP subnets etc.) ...
9
votes
6answers
3k views

Do network adapters read incoming bits in a single stream?

When a Gigabit network adapter is receiving data, how is it receiving the bits? Is it seeing it all in one stream of 0's and 1's? Or is there somehow multiple streams of 0's and 1's coming in at the ...
8
votes
2answers
1k views

Why do IPv6 unique local addresses have to have a /48 prefix?

According to RFC 4193, unique local addresses will always have a prefix of FD00::/8.. but according to Wikipedia: The block fd00::/8 is defined for /48 prefixes, formed by setting the forty least-...
7
votes
3answers
4k views

How is tcp/ip implemented

Well, first of all I am new to networking. And I have studied the layered structure of tcp/ip protocol stack. I know that the layered structure is an abstract model, but I didn't know how the ...
6
votes
2answers
1k views

Encapsulation: can a higher protocol encapsulate a lower protocol?

I've heard someone say that a protocol higher up the osi model can encapsulate a lower protocol. As far as I know, personally, a protocol can only encapsulate a same-level protocol or one at a ...
6
votes
2answers
787 views

is there a difference between Latency and speed ?

so latency is the time it takes for bits to get from the sender to the receiver and the speed is how fast bits travel , so logically the more speed the network has the more low latency it has ...
6
votes
2answers
960 views

What precisely is a link?

When reading about layer 2 the word "link" is frequently used but strangely I'm struggling to find a formal definition of it. What is the precise definition of a link? So in the image below, how many ...
5
votes
4answers
196 views

Packet Collison Avoidance

If a wireless network has collision avoidance, how comes the network slows down if more clients connect to it?
5
votes
2answers
439 views

APIPA and LAN Broadcast Domain

I just want to know can a Local Area Network broadcast domain be operated by only relying on APIPA?
4
votes
2answers
1k views

What does it mean to lease an IPv4 block?

When you lease an IPv4 block, what do you actually get? How do you get access to the IP addresses? Is there any special equipment required or is it as simple as renting a server?
4
votes
2answers
273 views

What is the best to simulate an RJ45 cable failure without changing switch configuration or removing the cable?

I am looking at an automation element for a training environment. We would like to be able to fail a cable without doing a shutdown on the interface or having an engineer physically remove the cable ...
4
votes
2answers
617 views

Juniper SRX answers all ping requests instead of forwarding

I have about 4 different subnetworks at my place, when i'm trying to ping to static device in subnetwork1 from subnetwork2 i always see that device pings, even if it's off. I assume my SRX300 answers ...
4
votes
2answers
61 views

Better throughput with 100 Mb NIC setting

Ran across something very odd today. Just had a symmetrical 100 Mb circuit installed at a site I’m contracting at. When the NIC is set for auto negotiate for duplex and speed, we only get ~96 Mb down ...
4
votes
1answer
244 views

General issues with access to and from DMZ on Cisco ASA 5520

I just got my software upgraded from v8.2(x) to v.9.1(7), but I have some general issues with access to and from my DMZ: No internet access from DMZ No access to web or mail server from outside to ...
4
votes
1answer
47 views

F5 BigIQ communication with BigIP

I'm new to F5. Basically a BigIQ centrally manages BigIP load balancers. In order to update the device, I have to login to the UI and apply the changes there. I would like to know how this is done (...
4
votes
2answers
223 views

Are network protocols and routing protocols different things?

When reading about network protocols it says they are a set of rules and format for communication between devices over a network, so basically an agreed way of how to communicate over a network. But ...
4
votes
1answer
1k views

What does 'parent interface' mean with respect to VLANs?

I'm trying to learn about VLANs by configuring a router with PFsense installed. Reading the documentation I came across the following sentence: The following example shows how to configure two ...
3
votes
2answers
90 views

Is it possible to limit a IP's traffic in gateway Juniper switch?

In my gateway Juniper Switch: ... irb { unit 0 { family inet; } unit 2 { family inet { address 10.10.10.254/24; } } unit 9 { family ...
3
votes
2answers
482 views

How is the term “fabric” defined in networking?

I know this is fundamental and I can find out in Google but so many people differ themselves when they talk about network "fabric". Kindly elaborate on this ?
3
votes
2answers
4k views

Can anyone explain to me the difference between the PSH and URG flags in TCP segment?

According to me when PSH flag is set, it indicates that data will have to be sent immediately to the wire and on receiving side the data has to be pushed to the application immediately. When URG flag ...
3
votes
1answer
83 views

How to secure an aging PC from the switch/router side?

I have an aging Windows XP PC whose purpose is to feed code to a manufacturing machine via a RS-232 connection using machine-specific software. The PC needs to retrieve its code from a network file ...
3
votes
2answers
902 views

Connect two routers to a single uplink for full redundancy

I have a single uplink with my ISP at a data center. I have 2 routers (CISCO 3850). How do I connect these routers to that uplink WITHOUT a network switch? That switch will be a single point of ...
3
votes
2answers
70 views

Cisco Router 1800 series doesn't route internet

Working on an issue with a 1800 series Cisco Router. Router get's Internet just fine, can ping Google, Microsoft, etc.. Router is connected to a switch, switch connects 2 workstations running Windows ...
3
votes
1answer
133 views

Cisco Router IOS update

I am facing problem in update the IOS of Cisco 7304 router. I am upgrading from 12.4(24)T2, to 15.2(4)S7 this. but I was boot from this version 15.2(4)S7 it booted proper from flash. But when I put ...
3
votes
1answer
61 views

Why we use transmission system like sonet sdh

Hello friends i have one query that we can connect routers and switches directly on fiber and with high capacity why we uses transmission system like sonet,sdh and dwdm?
3
votes
1answer
364 views

TCP layer behaviour upon receiving wrong sequence number

I have the IP and port details of an already established connection between the TCP server and the client. As I am simulating packet injection attack using the packETH tool, I disguise my self as the ...
3
votes
1answer
673 views

What is the difference between GPON ONU and ONT?

The Optical Network Unit (ONU) and the Optical Network Terminal (ONT) GEEPONs can both connect with an Optical Network Terminal (OLT) via fiber cables in order to achieve an Optical Distributed ...
3
votes
1answer
114 views

ASA 5505 cant access inside network from Anyconnect SSL Connection

So I have a ASA I can connect via SSL perfectly fine receiving internet.My issue is that I cannot ping any device on the network especially the inside network on my router. My topology is a ASA 5505 - ...
3
votes
1answer
422 views

Juniper SRX320 Dynamic VPN, cannot route to Remote-Protected-Resource

Multiple VPNs setup with a Juniper SRX320. The SRX320 has an irb interface as follows: irb { unit 0 { family inet { address 192.168.120.1/24; } } } I've setup ...
3
votes
1answer
2k views

How to connect 192.168.1.x network to 192.168.100.x gateway?

Hello fellow networkers. I am very new to this world and don't know a great deal about IP addresses and subnetting. I however stumbled upon quite a big problem (for me at least - haha) My entire ...
3
votes
2answers
5k views

SSL/TLS belongs to which OSI layer [duplicate]

Can someone please explain SSL/TLS belongs to which OSI layer. I have been looking through many sites and all of them have different options of Application, Presentation and Session.
3
votes
1answer
399 views

Cisco SG300 and Fortigate 90D integration

I need help in setting up my network, currently I have the following setup. All the computers can browse the internet but when I tried to create a two groups (a group that can access the internet and ...
3
votes
0answers
110 views

Can I do Q-in-Q vlans between Dell and Cisco switch

Our Head Office is connected to our DR location between an L2 tunnel provided by our ISP. I need to establish a Q-in-Q setup between both sides to pass multiple VLANs through. Our head office has a ...
2
votes
2answers
64 views

Relationship between full duplex and speed

Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time. but my question is if we have an interface with 100Mb speed and full-duplex ...
2
votes
2answers
204 views

Can a single subnet work across several switches?

New to networking and studying hard but limited access to a kit to try things at the moment... My question is - if I had, for example, two Layer-2 switches cable connected, could I have devices on ...
2
votes
1answer
60 views

How does a packet find its way from a LAN device to a router, or vice versus?

I am trying to understand how packets are sent from one device to another in a wireless network? (Perhaps the same question also applies to a wired network) How does a router know in which physical ...
2
votes
4answers
59 views

P2P Connections

Hey there I am a noob in the field of networking and I have a confusion: What is the difference between point-to-point and end-to-end connection ?
2
votes
1answer
65 views

Does UDP perform packet re-ordering at the destination?

User Datagram Protocol is a simpler message-based connectionless protocol. Connectionless protocols do not set up a dedicated end-to-end connection. Communication is achieved by transmitting ...
2
votes
1answer
181 views

How do I resolve connection issues between two 10/100Base-Tx to 100Base-Fx fast Ethernet converters

My network at two points, A and B, have the same connection devices that have been working well until recently. A (A is the internet entry point) transmits internet to B (B is the data centre) and B ...
2
votes
2answers
120 views

What defines a “home address”/“home network”? (Computer Networking)

In Computer Networking, and in particular to WiFi-networks, we learn that a "mobile node" (i.e. any mobile unit that can access a router through WiFi) has a permanent IP-address (the "home address"), ...
2
votes
2answers
763 views

what is the difference between cable and dial up modem?

so the dial up modem allows you to access the Internet by converting digital data into analog signals that can travel through the telephone lines , and on the receiving end that modem will ...
2
votes
1answer
56 views

What are network port maps and what are they used for by the networking team in an organization?

I am curious to know what information generally the port maps contain.
2
votes
2answers
77 views

Why the three-way handshake use so short time accomplish it?

I use the Wireshark captured the packages: in there you see the number 1594-1596, the three-way hankshake only use 0.0002s(0.2ms) it complete it. but when I in the server(103.215.9.27) ping the ...
2
votes
1answer
218 views

Collect UDP packets lost during iPerf test

I'm testing my network infrastructure where I'm using iPerf and UDP protocol. I'm using the following: On the server side: ubuntu@ip-172-0-1-11:~$ iperf -s -u and the client side: ubuntu@ip-172-2-...
2
votes
1answer
69 views

How do I know what is the origin IP if I ping from a router to a host of an external network in packet tracer?

When we ping from a router to a host in an external network, how do we know what is the origin IP of the packet? I searched and I didn't find a way to select which interface is the starting point of ...
2
votes
1answer
80 views

Defining what type of casting based on IPv4 address

I'm kinda new to networking. I have a small question, how can I determine what type of casting (unicast, multicast or broadcast) is it based on IPv4 address. For example: 142.55.172.200 I tried to ...
2
votes
2answers
85 views

Dose Huawei S6720 have GE port?

everyone! I want to buy a Huawei switch with GE ports, does Huawei S6720 model have GE port?
2
votes
2answers
509 views

what is a networking protocol?

i just want to start by saying that I classify my self as a beginner in networking and my only hope is to become very good as you are,so i was reading this book and i didn't understand the term ...

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