Questions tagged [layer2]
For questions about the OSI layer-2 (data-link layer).
279
questions
-2
votes
0answers
14 views
Error Detection and Correction in the data link layer [closed]
compare and contrast the difference between checksum, CRC and Hamming codes in terms of their Hamming distance and explain advantages and disadvantages of each of them.
Can someone please their ...
0
votes
3answers
42 views
Using MSTP with RSTP
I have two layer-3 switches connected with two redundant links that I'm trying to run PTP OSPF sessions across, a la:
(OSPF)
VLAN 1002
- - - - - - - - - - - -
/ ...
0
votes
2answers
29 views
If we already have default VLAN, Why we need Native VLAN? [duplicate]
What is the need of Native VLAN and default VLAN. How they are related?
Can Somebody explain this in detail?
0
votes
0answers
12 views
Understanding OSI communication model from Electronics Perspective [duplicate]
I have gone through the OSI communication model and the associated levels.
But I do not understand on how is this implemented in the Hardware level. Or let me put it like this.
Suppose we have a USB ...
0
votes
2answers
35 views
How are packets ( received from the server ) sent to the host from the gateway ( which is present in the host network )?
If the host is receiving packets from a server, these packets have a destination IP address of the host and it is first received by the gateway present in the host network. Now the gateway checks the ...
1
vote
2answers
48 views
Question on ARP
Given the above diagram, is it correct to say that the ARP cache table in PC A contains the IP-MAC addresses for PC B and the router, while the ARP cache table in PC B contains the IP-MAC addresses ...
0
votes
1answer
28 views
How does a 802.11 (wifi) frame identify the payload's layer 3 protocol?
My understanding is that the 802.11 frame header is an equivalent of ether header. In the ether header, there is an EtherType field that identifies the payload protocol, such as IPv4/IPv6/ARP etc. ...
1
vote
1answer
27 views
How do (LANCOM) Tag-Based vlan groups work and on which vlan does the device respond?
I just started a new job and part of it is to manage and maintain the ICT. As the previous network/system engineer left the company i'm on my own to figure out how everything works.
I have ...
0
votes
1answer
61 views
EXOS layer2 Configure on a Summit x440-G2-24p
I search since Days for a working configuration for a layer2 connection from another extreme switch to this switch. What I connected Physically on my Summit x440-G2-24p:
the ethernet(lan) cable from ...
0
votes
3answers
102 views
Clarification on when routers encapsulate and decapsulate packets
I'm an application developer working on getting a working knowledge of network engineering, so basically a newbie. I've been trying to figure out exactly when routers decapsulate frames into packets ...
1
vote
1answer
64 views
How do computers send switches packets, if switches don't have IP or MAC addresses?
I am new to networking, so please excuse me if I am saying stupid stuff.
From my understanding, PCs are sending packets to switches, which then decide which physical port to forward that packet to. ...
-1
votes
2answers
46 views
Switch Operation Beyond VLAN Segmentation
What are the other operations performed by a switch which are outside the VLAN's boundaries.
Is Logical (VLAN) Segregation is exactly same as breaking a switching network physically via a Router?
1
vote
1answer
38 views
CRC R bit size to guarantee error free
For a Link Layer frame, it's common to include some bits for redundancy. Suppose we have a frame
with X bits of actual data, and want Y bits of error-correction bits.
What size do we need to choose ...
2
votes
2answers
104 views
Why can't we assign MAC addresses on our own?
Mac addresses are used in networks, not in internetworks. So, why to not create a protocol, that will automatically assign to connected devices MAC address in that way, so they don't repeat in network?...
1
vote
2answers
278 views
PPP, Ethernet and PPPoE differences
Correct me if I'm wrong.
So,
Ethernet technology is being primarily used in LANs. And we use PPP in serial links. To carry IP datagram, we can use either layer 2 technology, such as Ethernet, or we ...
2
votes
1answer
42 views
Is an IP broadcast always a layer 2 broadcast also
On my PC I see 255.255.255.255 in ARP with MAC FF:FF:FF:FF:FF:FF, so I'm assuming that in most cases the L3 broadcast is also encapsulated into an L2 broadcast frame, but is this standardized?
For a ...
1
vote
1answer
23 views
Question about MTUs vs maximum frame sizes - what is their difference?
I am currently studying networking at university and I have a question about MTUs and maximum frame sizes.
What is the difference between the MTU and the maximum frame size? This Wikipedia article ...
4
votes
2answers
738 views
Confusion about data fragmentation/MTUs - why was it introduced in the first place?
I am currently studying networking as a part of my bachelors and I am a bit confused about why fragmentation/MTUs are necessary. In my lecture slides, it only says "Fragmenting if necessary" under the ...
1
vote
2answers
87 views
Question about the destination IP inside an IPv4 packet
I'm reading about link and network layers for the first time and I'm trying to put the pieces together to understand how they work together. My question may not have to do with the link layer but I'm ...
1
vote
1answer
40 views
2 machines can have the same link-local address, in the correct context. What context?
I don't get in what context multiple interfaces/machines can have the same link-local address. Thanks in advance.
3
votes
1answer
72 views
Query on PTP Transparent Clock
I had a query in PTP Transparent Clock(TC), Please consider the below picture for my question.
I will try to express my question with the help of a real world example
Say, two places Place_A <----...
0
votes
1answer
203 views
Why is default gateway in routers configuration usually set as an IP address?
I mean why not just:
a MAC address? It should eliminate the need in ARP requests asking for gateway address. Also it should eliminate the need in changing IP addresses in settings when gateway IP is ...
2
votes
1answer
412 views
What is the purpose of native VLAN on a trunk link?
Most VLAN articles I've read recommend avoid using VLAN1 for ports with untagged traffic (aka access ports). I've heard enough of this nonsense. Except for the reserved values of 0x000 and 0xFFF, a ...
4
votes
2answers
459 views
Is a datagram from an upper network layer converted 1:1 to one of the lower layer?
I know datagrams from upper layers are converted to those of lower layers by adding metadata, but I cannot seem to find this information anywhere. Which one of the below is correct?
A single TCP ...
0
votes
1answer
594 views
Logical Link Control (LLC) vs Medium Access Control (MAC)
What differs the LLC sublayer from the MAC sublayer?
From what I've understood
- The MAC sublayer does what the PHY layer should be doing: detection (error, collision), channel listening, analog-to-...
0
votes
1answer
38 views
Unicast Adjacency Routes Nexus (AM) Cisco Nexus
I have an odd situation. There is static route on my Nexus 7700 that routes anything for specific subnet /24 to a F5 LTM Load Balancer, external VRRP interface 10.x.153.15.
As you can see below, ...
1
vote
2answers
221 views
Clock Synchronization in a Network
I had a query in Clock Synchronization in a LAN.. If we already have clock synchronization in a network with the help of preamble field in an Ethernet frame.
Why should we need still protocols such ...
1
vote
1answer
58 views
Is TCP aware of MAC adress
lets say I would like to make connection between client and server on port 80. Is 3 way handshake aware of server MAC address? I mean: client send SYN data packet to specific IP:port and MAC. In ...
0
votes
1answer
63 views
Is there any fixed version of CSMA/CA?
I was trying to understand exact algorithm for Carrier Sense Multiple Access / Collision Avoidance mechanism from Forouzan's book. The book gives very detail explanation of topics. However explanation ...
0
votes
1answer
242 views
What is the theoretical difference between the link layer and the network layer?
I have run into this problem again and again and have never found a sufficient answer to this question. I want to understand the fundamental, theoretical difference between a layer 2 network and a ...
0
votes
1answer
52 views
N2K-C2248TP-1GE question
We are working with Cisco 2960 and Cisco 4948 switches as our top of rack switches and we want to purchase some N2K-C2248TP-1GE , and connect N2K-C2248TP-1GE to our edge switches, (our edge switches ...
0
votes
3answers
92 views
Regarding Cisco's hierarchical network design
why routed ports usually implemented between the distribution layer and the core layer ? why not just extend the layer 2 domain to the core layer ? is the other design model more practical than this ...
2
votes
2answers
358 views
Router on a stick not connecting 2 different VLANs
I have a setup which requires two different VLANs to be able to ping one another. I have a setup with 2 - layer 2 switches and a router that has defined sub-interfaces, and for the life of me, I ...
0
votes
1answer
25 views
Broadcast Timer [duplicate]
This question is regarding in the process of L2 MAC Address learning.
As we know, if a sender sends a packet to some receiver host which switch doesn't know, it will broadcast for learning.
Assume an ...
1
vote
1answer
336 views
Ping across VLANs using layer 2 switch
I'm trying to ping one PC on one particular VLAN (VLAN 80) from another PC on a different VLAN (VLAN 50). I have a layer 2 switch (Cisco 2950T), so I can't do it from within itself.
How would I be ...
0
votes
2answers
223 views
Different MAC addresses [closed]
What happens if a host on the network receives an IP packet with a MAC source address that differs from the MAC address in the local ARP table for that source IP.
The ARP table entry for that IP was ...
2
votes
1answer
62 views
What's the LAG interface period be if the two switches have different periods set
Considering a LAG interface between two devices A and B, A is configured to have LACP fast transmission and B to be LACP slow what would be the resulting aggregate interface's period be?
1
vote
2answers
216 views
Is a “LAN” a layer 2 or a layer 3 concept, in TCP/IP?
I think my question is purely theoretical and a matter of definitions; it derives from the fact that a L2-switch with VLAN capabilities is able to "create" different virtual LANs, and thus I am led to ...
4
votes
3answers
372 views
JunOS, access mode interface asks for a vlan
I'm kinda new to networking so I'm going to do my best to try explain my issue.
The issue that I have is that I want to delete all default configuration for my xe interface.
Current configuration:
...
0
votes
1answer
84 views
Layer 2 and Layer 3 traffic with one cable
Hers the topology.
L2 switch
L3 switch
Router
There are 2 VLANs. One VLAN ends on the L3 switch 1 VLAN on the router.
Here is the question. Can i connect the L3 switch and the router with just 1 ...
3
votes
1answer
74 views
Bit stuffing and Error correction combined
If I understand correctly both error detection/correction and framing are done at the link layer. I understand how popular error detection/correction and framing techniques work. But I struggle with ...
3
votes
2answers
256 views
What are neighboring ports?
I know this is as basic as it gets but I can't find a direct answer to this question.
Are they ports on two different switches (or routers) that are connected by a cable?
Are they the ports ...
1
vote
1answer
260 views
Flooding vs Unknown Unicast Flooding
Can someone clarify what is the difference between Flooding and Unknown Unicast Flooding?
Is it the same thing or it contains different meaning?
I'm aware that Flooding happens when a switch ...
3
votes
1answer
1k views
Difference between Giant Frame and Jumbo Frame
Can someone enlighten me the difference between Giant Frame and Jumbo Frame?
From what I hear, Giant frame is a frame with the size greater than 1518 Bytes excluding Preamble, Frame Delimiter and ...
3
votes
3answers
627 views
Collision domain question
I'm studying for my CCENT exam, and not quite sure why the book (official Cisco) says that there are 5 collision domains in this example. Isn't it supposed to be 4? The hub on the left, the hub in the ...
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 ...
0
votes
1answer
85 views
Wireshark remote hosts
I configured a rip network. I connected two PCS to router 1, router 1 is connected to router 2 and PC 3 is connected to router 2. When I pinged PC 3 and looked at this in wireshark, in the source it ...
0
votes
1answer
162 views
sequence number layer 4 vs sequence number LLC layer 2
I had read about TCP in layer 4 where sequence number and acknowledgment numbers were assigned to each segment so that each side of the connection could keep track of the process of sending/receiving ...
2
votes
2answers
231 views
Please help me understand this simple arp request / reply - how does a router know an IP address without knowing the MAC address?
I am new to networking, I am using Wireshark on my home PC to learn about ARP. I understand that ARP is used to build the ARP cache, which correlates IP addresses to MAC addresses on a LAN. ARP ...
3
votes
2answers
91 views
How does ethernet understand what is the upper layer? What are the values in Ethernet II field?
How does ethernet understand what is the upper layer of a frame? What are the values in Ethernet II field?
Ethernet is in data link layer, so the upper layer is network layer.
When processing at ...
