Questions tagged [layer2]

For questions about the OSI layer-2 (data-link layer).

Filter by
Sorted by
Tagged with
0 votes
0 answers
9 views

Options for building a layer 2 tunnel or VPN from a windows machine to a VMware network? [closed]

What options are there for building a layer 2 tunnel or VPN from a windows machine to a VMware network ("Virtual Machine port group for a Standard Switch")? I want to have a network ...
Azendale's user avatar
  • 111
0 votes
2 answers
24 views

RSTP convergence of p2p links

Ramping up on RSTP here. One thing that is unclear to me is how RSTP links converge initially on P2P links. Consider the classic 3 switch topo as below: For RSTP, won't all the links move to ...
host_unreachable's user avatar
0 votes
1 answer
60 views

How do layer 2 switches route based on MAC when daisy-chained?

Trying to think about this from a hardware design perspective, if I had to design an FPGA or a uC or something to manage a single port being the gateway port and one or more switched ports for routing,...
Qix - MONICA WAS MISTREATED's user avatar
2 votes
2 answers
84 views

How can a router not recognize a gratuitous ARP MITM attack?

I'm reading the chapter for DHCP Snooping/DAI in the OCG for the CCNA and I have a question regarding how gratuitous ARP message attacks work. I'm sure there is a piece I am missing, but I've searched ...
Alex's user avatar
  • 21
0 votes
2 answers
76 views

How does L2 switch forward tagged VLAN?

I am a student of networking and have a question. I am currently doing an internship / project at a school where they have 3 buildings. I will name them for now A (subnet 172.16.x.x) --> Each with ...
Bartballon's user avatar
1 vote
1 answer
213 views

Understanding IPv4 model of operation

I'm new to networking and reading RFC791 about IP protocol specification and got some question regarding the paragraph 2.2 Model of Operation. Here is what is discribed: The internet module prepares a ...
Some Name's user avatar
  • 121
0 votes
3 answers
99 views

If all subnets are a part of same vlan, then the network segregation using subnets does not make sense

This is what we know about subnetting. By dividing a network into subnets, you can separate different departments, locations, or security zones, creating distinct broadcast domains. This segmentation ...
RRHS's user avatar
  • 395
0 votes
1 answer
40 views

how can a STP switch time out MAC addresses from the table in Listening state?

I am looking over some materials describing STP's port states (the original version from 802.1d) and they say that a port in Listening state can not modify the MAC address table (it doesn't learn new ...
Marcus's user avatar
  • 183
0 votes
0 answers
23 views

Why are connected switches not a good substitute for the network layer? [duplicate]

Unless I am missing something, because switches can be chained together, I am not sure why the network layer is needed. Theoretically, one can dedicate a frame to any MAC address, and assuming there ...
Aviv Aviv's user avatar
  • 109
0 votes
3 answers
116 views

One layer 2 switch in the middle of router network

In general, The connection should be like PC---SW---ROUTER---Many ISP router---Router---SW---PC so the packet will be from layer 2 ---layer 3---layer 2 What if I put one layer 2 switch in the network ...
jacky chong's user avatar
0 votes
0 answers
14 views

Are ARP messages always used for the process of "Flooding" even when layer-3 is not involved? [duplicate]

I'm new to learning networking so please bear with me. I've learned that ARP messages and flooding are used to find mac addresses when IP addresses are involved. I've learned that when the mac address ...
William's user avatar
  • 101
0 votes
1 answer
61 views

What datalink protocol is used in aircraft to ground station communication? [closed]

Laptops, mobile devices, and smart TVs communicate to access point via WiFi. Wireless peripherals (mouse / keyboard) communicate to workstations via Bluetooth. Mobile phones communicate to base ...
Noob_Guy's user avatar
  • 471
0 votes
1 answer
70 views

I am trying to wrap my head around NDP

I know before PC10 can ping PC11 it will use IPv6 Neighbor Discovery to resolve the Destination MAC address for layer 2 header. But what would the DEST MAC ADDR be and what topics can I learn this
s3lectstar's user avatar
0 votes
4 answers
902 views

Communication between different VLANs

In my previous understanding, there is no way to communicate between two VLANs using only layer 2. After all, this is the purpose of having VLAN. I found a forum that claims the following. 1.VLANs can ...
jacky chong's user avatar
1 vote
2 answers
164 views

Differences between TCP congestion and TCP flow control

From my understanding, flow control essentially how much the receiver can process. Suppose I can send packets at 100mb/s but the receiver can only process information at 10mb/s, flow control would ...
Randy's user avatar
  • 13
1 vote
1 answer
149 views

What happens if the layer 2 destination MAC address mismatches?

I was wondering, what happens if I send a packet with layer 2 destination (say 1ebf) different that what will receive it, lets say a router (mac 22ff) recieves it. Will it drop the packet? Or ...
AlazOz's user avatar
  • 13
1 vote
1 answer
465 views

Can a switch fragment a jumbo frame?

In all resources seen that tackle the term of "jumbo frame", I understand that it is applied in a LAN, because: It's a Jumbo frame, and a frame is for Layer 2 These resources talk a lot ...
Lee's user avatar
  • 63
3 votes
1 answer
374 views

Length of Ethernet Preamble on 10Gb network

I know (see https://en.wikipedia.org/wiki/Ethernet_frame) that an Ethernet frame includes a 7 byte preamble of 0x55s and a one byte start frame delimiter (SFD) 0xD5, for a total of 8 bytes before the ...
Erik Parkinson's user avatar
2 votes
1 answer
253 views

What's the difference between MTU and MRU ? How come people talk so often about MTU and little consideration is given to MRU?

I don't understand why MRU isn't mentioned as frequently as its counterpart MTU. Are they always arranged to have the same value on a device ? A few days ago I noticed that my Windows machine accepted ...
Kode1000's user avatar
2 votes
1 answer
329 views

MTU mismatch scenario, two hosts handle in a different way ingoing packets bigger than local interface MTU. How does MTU really work?

I’ve been struggling with the MTU topic for a while and I still can’t get how it really works. The majority of books that I read and the courses that I attended all seem to treat this subject in a ...
Kode1000's user avatar
0 votes
2 answers
90 views

Where is priority for a particular frame set?

The Medium Access Control sublayer appends 3 bits for the priority of the frame. The possible choices for the priority are Traffic Type Priority Background 0 (lowest) Best effort 1 (default) ...
user84425's user avatar
8 votes
6 answers
4k views

How Does A Layer 2 Switch Differentiate Between Different Networks?

I know that different IP-based networks can be connected to the same layer-2 switch. and I know each network's nodes can communicate just fine, however, no normal traffic can occur between two nodes ...
Shadi's user avatar
  • 285
2 votes
1 answer
491 views

Ethernet: How does receiver know end of frame? [duplicate]

I need to implement an 'ethernet-wannabe protocol' with a sender and a receiver.(only layers 1,2). Assuming a sender\receiver model for an Ethernet frame with varying payload length. As for the sender-...
Danny Blozrov's user avatar
0 votes
3 answers
179 views

Do telephone calls work at Layer2?

We know that Wi-Fi works in both layer1 and layer2 and travel through air in layer1. My question is when we create mobile phone call during connection establishment phase sender Mac address and ...
S. M.'s user avatar
  • 358
1 vote
3 answers
464 views

Why switch uses Mac address during implementation of spanning tree protocol (STP)?

We know that layer2 switch doesn't use Mac address ,uses only certain port number to accept the frame. But I have been read on book as well as internet that uses Mac address to find spanning tree for ...
S. M.'s user avatar
  • 358
0 votes
1 answer
246 views

How FDB (Filtering Database) is filled out

I would like to understand what is used as a VLAN column in the FDB. For ACCESS port it is PVID if frame untagged or frame VID if frame is tagged, for TRUNK it is allowed VLANs? We can represent the ...
Manticore's user avatar
  • 131
2 votes
1 answer
126 views

Fragments taking different routes?

I have trouble understanding why sometimes it occurs that during IP fragmentation certain fragments take different routes. I was following this the second example: https://www.gatevidyalay.com/ip-...
mato_kan's user avatar
1 vote
1 answer
262 views

Why need Ack flag if we already have ack number in TCP

If we have ack number so from there we can trace that how many bytes are received and which byte is need next so then what is the use of Ack flag there?
user83095's user avatar
0 votes
2 answers
623 views

How PPPoE uses addressing to know destination Mac address?

Case.1 We know that when router connected via point to point(PPP) protocol then ARP isn't used to know the destination Mac address. Case.2 When two router connected via PPP as well as Ethernet which ...
S. M.'s user avatar
  • 358
1 vote
1 answer
112 views

How n level come to know the n+1 level contents?

Suppose in application layer is running some application. And application has respective source port number and destination port number. And know that n layer has no authentication to know about n+1 ...
S. M.'s user avatar
  • 358
1 vote
1 answer
212 views

Router could get packet of size more than 1500 bytes?

Suppose transport layer get the segment 4000 bytes from application layer at sender site. But we know maximum MTU in layer2(Ethernet) is 1500 bytes. My question is so fragmentation is happening at ...
S. M.'s user avatar
  • 358
0 votes
1 answer
268 views

What is the differences between flow control and access control?

We first apply access control methods to get access to the channel link followed by the flow control methods to stop the receiver from overflowing. Suppose we are using CSMA/CD in access control ...
S. M.'s user avatar
  • 358
0 votes
1 answer
99 views

Understand router Ip address and Mac address, Switch Mac address

Scenario:1 Suppose external Router R1 has interface a connected with interface b of the site Router R2. And Router R1 using IP address 80.0.0.0/8 for a. Router R2 has 4 subnets 80.0.0.0/10, 80.64.0....
S. M.'s user avatar
  • 358
0 votes
3 answers
318 views

How NAT router use layer4 contents in layer3?

I followed from this question and @PeterGreen's Answer , and come to know that NAT router working in layer3, but using layer4 contents(layer4 port number,layer4 checksum). My question is when layer3 ...
S. M.'s user avatar
  • 358
0 votes
2 answers
474 views

Acknowledgement, retransmission of layer2 is actually belongs to layer4?

I followed from this question understand that only transport layer responsible for acknowledgement. But I have read on book stop and wait, GBN, SR protocols uses acknowledgement, retransmission in ...
S. M.'s user avatar
  • 358
0 votes
2 answers
458 views

What is responsibility of different layers of OSI model and intermediate devices between sender and receiver when data packets are lost/corrupted?

Suppose sender sending some data to receiver and there are 3 routers between them. R1, R2, R3 are routers. Now sender starts sending data packet D through it's AL, TL, N/W L, DLL,PL to router R1 ...
S. M.'s user avatar
  • 358
1 vote
1 answer
331 views

EtherType multiplexing used by LLC layer

What's the type of multiplexing used by Ethernet (LLC layer)? It says in Wikipedia "The LLC sublayer provides multiplexing mechanisms that make it possible for several network protocols (e.g. IP, ...
ragnar's user avatar
  • 17
0 votes
2 answers
134 views

Ethernet compatibility

I am improving my knowledge about the Ethernet protocol. During my study, I noticed that they are multiple versions of the protocol. Example: 2.5GBASE-T and 5GBASE-T and 100BASE-TX. I wonder depending ...
ragnar's user avatar
  • 17
0 votes
0 answers
29 views

Why collision domain occurs in hubs but not switches [duplicate]

if anyone knows the actual point and in depth answer to my question please help. the links in the comments didn't helped at all Most of the websites which i saw are just vaguely saying that collision ...
vinter's user avatar
  • 101
1 vote
2 answers
310 views

Best way to configure layer 2 daisy chain with 2 layer 3 switches/gateways at either end?

I would like to implement a linear daisy chain for the purpose of transmitting internet over a considerable distance. One motivation behind the use of a linear daisy chain for this problem is that ...
Doug's user avatar
  • 13
0 votes
1 answer
330 views

Total delay of virtual circuit switching? [closed]

We know that virtual circuit switching(VCS) has both features of circuit switching and datagram switching. It uses connection oriented path but may or may not dedicated that means resources may or may ...
S. M.'s user avatar
  • 358
0 votes
1 answer
840 views

Why or when do we need Layer 2 NAT? [closed]

What is the point of public addresses in Layer 2? Why or when do we need it? When is it healthy to use? Or is it even a common thing? Sorry I am kinda new at networking and I just googled it but ...
Red And Black's user avatar
0 votes
1 answer
33 views

Does the length of a frame influence the likelihood of a collision?

Considering two separate analog signals on the same frequency transmitting digital data that represents a frame, from my understanding if any portion of the two signals overlap, this is a collision. ...
user4779's user avatar
  • 115
1 vote
0 answers
88 views

Logs on my Cisco ASA show the public gateway (ISP router) is pinging the internal network, how? [closed]

Im (remotely) working with an issue where the network has intermittent drops. i suspect possible routing loop, but havent confirmed that yet. In the logs of our Cisco ASA 5506, i see that the public ...
TechEng's user avatar
  • 21
1 vote
1 answer
625 views

Does a router work both on Layer 2 and Layer 3? [duplicate]

According to TCP/IP model router works at Layer 3. But when data has to be transmitted to different network it is based on IP address but hop-to-hop transmission is based on MAC address. That means ...
Rohit's user avatar
  • 31
0 votes
1 answer
401 views

Passing Modbus TCP/IP nodes (connected in multiple VLANS, same network) via Toffino firewall

I have been assigned to check the security aspect of the below network shown in image. When i asked question on security of individual modbus device, I was told to create individual vlans for each ...
Srikanth Chilivery's user avatar
4 votes
2 answers
740 views

Why two routers connected via PPP don't use ARP but Ethernet requires ARP?

I have read from @Ron Maupin's answer of this question that your two routers are connected via PPP (this is not uncommon), ARP will not be used , but if the two routers are connected via ethernet, ...
S. M.'s user avatar
  • 358
5 votes
4 answers
3k views

Is there a ping equivalent on layer 2?

You can use ping to measure RTT between you and an IP host and thereby confirm connectivity. Is there an equivalent that can be used on L2/Ethernet with MAC addresses? i.e. l2ping AA:BB:CC:DD:EE:FF (I ...
Atemu's user avatar
  • 153
1 vote
2 answers
1k views

How is P actually chosen in P-persistent CSMA?

I am struggling to understand how the probability value P is chosen for P-persistent CSMA for any particular station, what's the logic behind this.I have read from Wikipedia . P-persistent This ...
S. M.'s user avatar
  • 358
0 votes
1 answer
48 views

Does creating frames done by device drivers?

If I got it right, TCP and IP packets are created normally by software running in the kernel. So when I as a user open up a socket of type TCP/IP and send a message, the kernel takes care of all those ...
YoavKlein's user avatar
  • 137

1
2 3 4 5
8