Questions tagged [layer2]

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

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44 views

Vlan vs. Subnet Broadcast Domain

It is my understanding that Vlans separate broadcast domains, but I often see people say, "subnets define a broadcast domain" as well. Is it correct to say, "Vlans define a L2 broadcast domain, and ...
3
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2answers
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 ...
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0answers
15 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 ...
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3answers
46 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 - - - - - - - - - - - - / ...
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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?
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0answers
13 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 ...
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1answer
64 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 ...
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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 ...
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4answers
2k views

Accessing devices on different subnets using a switch

I have two devices which come up with default IP addresses: Device 1 - 192.168.168.168 mask 255.255.255.0 Device 2 - 192.168.1.254 mask 255.255.255.0 I can commonly deduce that both the devices ...
1
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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 ...
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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 ...
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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. ...
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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 ...
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3answers
105 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 ...
5
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6answers
18k views

Difference between routing, forwarding, switching

I feel like the three terms are often used as synonyms but actually all mean something different. I did look at Wikipedia sites but I'm still unsure about the definitions of the three. From my ...
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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. ...
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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?
7
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3answers
11k views

What is the difference between layer-2 and layer-3 broadcasts? Please explain with an example

What is the difference between broadcast addresses ff.ff.ff.ff.ff.ff (Layer 2) and 255.255.255.255 (Layer 3)?
2
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2answers
105 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?...
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2answers
307 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
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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 ...
4
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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
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1answer
24 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 ...
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2answers
89 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 ...
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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.
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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 <----...
4
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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
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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
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1answer
427 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 ...
1
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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 ...
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5answers
332 views

What blocks a computer from another network in the same switch from answering an ARP request?

Let's suppose I have 3 computers A, B and C connected to the same switch with only the native VLAN active. A and B belong to the same network, let's say that their IP addresses are 192.168.1.1/24 for ...
6
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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
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1answer
604 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-...
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1answer
64 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
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1answer
42 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, ...
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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 ...
0
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1answer
256 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
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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
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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 ...
1
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1answer
341 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 ...
2
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2answers
365 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
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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 ...
3
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2answers
8k views

ping in pure layer 2 LAN [closed]

How can I ping a specific IP on a network which only contain switches while switches as far as I know don't understand IPs but only MAC!
0
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2answers
226 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
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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?
3
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3answers
630 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 ...
1
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2answers
217 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
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3answers
374 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
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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 ...
2
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2answers
934 views

How can we identify layer two device in a network or what are those device effects on a frame

This is sample of a traceroute to google.com: TraceRoute from Network-Tools.com to 216.58.194.46 [google.com] Hop (ms) (ms) (ms) IP Address Host name 1 0 0 0 ...

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