23
votes
Accepted
What do TCP/UDP add to "raw ip"?
IP is a Layer 3 protocol. TCP/UDP are Layer 4 protocols. They each serve different purposes.
Layer 3 is in charge of end to end delivery. Its sole function is adding whatever is necessary to a packet ...
- 14.8k
22
votes
Accepted
Can a router send ARP requests to hosts?
ARP is used by a host on a LAN to resolve a layer-3 address to a layer-2 address so that a frame can be built for the LAN. A router is just another host on a LAN, and it will need to resolve layer-3 ...
- 98.3k
17
votes
Accepted
VXLAN vs VLAN over layer 3
Yes, from the packet switching point-of-view, VXLAN is just a matter of sticking some encapsulation on top of an L2 frame: something that other protocols do as well.
The real difference it makes is ...
- 2,406
17
votes
How Does A Layer 2 Switch Differentiate Between Different Networks?
A (layer-2) switch doesn't care at all about the IP networks you run through it.
however, no normal traffic can occur between two nodes on two different networks.
That is correct. Different IP ...
- 81.5k
14
votes
Accepted
Does a switch understand packets? If yes, what is the frame terminology for?
You need to understand the concept of layers.
An application will send data to the Transport Layer. The Transport Layer protocol will encapsulate the data inside headers for the Transport Layer ...
- 98.3k
13
votes
Accepted
RIB vs FIB differences?
The forwarding information base (FIB) is the actual information that a routing/switching device uses to choose the interface that a given packet will use for egress. For example, the FIB might be ...
- 6,104
12
votes
What is a "Layer 3 Switch"?
Managed switches are in simple terms switches that can be "managed." Managed means that they can provide information/statistics about their operation and usually that they can be configured. While the ...
- 27.2k
12
votes
Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page?
The original RFC for ICMP, RFC777 state that:
ICMP, uses the basic support of IP as if it were a higher level
protocol, however, ICMP is actually an integral part of IP, and must
be implemented by ...
- 19.4k
11
votes
Accepted
Advantage of layer 3 switch over Router
In general, layer-3 switches move packets faster (near line rate) because everything they do is in hardware. They tend to be cheaper and cheaper to operate (power, personnel, etc.) vs. a comparable ...
- 31.5k
11
votes
Accepted
Do layer 3 protocols use layer 2 protocols?
Layer 3 (mostly IP) generally relies on the underlying layer-2 network (mostly Ethernet or Wi-Fi) for delivery. Just like a layer-2 network uses layer-1 links to actually move the bits.
The ...
- 81.5k
10
votes
Accepted
Difference between routing, forwarding, and switching
In general, forwarding refers to a device sending a datagram to the next device in the path to the destination, switching refers to moving a datagram from one interface to another within a device, and ...
- 98.3k
10
votes
Accepted
At which layer does router operate?
Network address translation (NAT) is a feature of Router which is
required for routing traffic.
That is completely incorrect. NAT is a kludge (a clumsy, inefficient solution) designed to extend the ...
- 98.3k
10
votes
How does Deep Packet Inspection work with encrypted packets?
As you point out, traditional DPI methods have limited ability to deal with encrypted traffic completely. They can still address encrypted traffic at a surface level at the very least, but it does ...
- 27.2k
9
votes
Accepted
What is the difference between layer-2 and layer-3 broadcasts? Please explain with an example
You need to understand the difference between layer-2 and layer-3 for an answer to have any real meaning for you, and I suspect you don't.
A layer-2 network is a LAN, and all hosts on it are peers. A ...
- 98.3k
9
votes
Does a router send frames or packets?
it seems that routers decapsulate the frame on arrival, and
encapsulate the packet in a frame in order to send it.
Yes. A router must strip off the layer-2 frame in order to get to the layer-3 ...
- 98.3k
9
votes
Is static routing used in large networks?
I work at a large ISP and before at a different large ISP and both networks extensively use static routing. Mostly on the firewalls as they don’t want to run an IGP or BGP on the firewalls, but you ...
- 257
9
votes
Accepted
How Does A Layer 2 Switch Differentiate Between Different Networks?
The switch doesn't even "see" what is going on above MAC layer. However, hosts are usually configured to send packets to another IP subnet via a default-gateway IP address. So the hosts ...
- 1,591
8
votes
What layer of the OSI model does NAT work?
Nat is a cross-layer process. It involves at least layers 3 (IP) and 4 (TCP, UDP, etc). In some cases it can also involve layer 7 (application).
A one to one NAT needs at minimum to modify the IP ...
- 13k
8
votes
What do TCP/UDP add to "raw ip"?
IP can transmit data just fine, the problem is what happens when that data gets to the other end. The only identification information is the IP addresses of the hosts and a protocol number. Neither of ...
- 13k
8
votes
Accepted
Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page?
There is much controversy about which protocols run at which layers in the models. Understand that the models, e.g. OSI Model, are just models, and the real world is often different.
There are ...
- 98.3k
8
votes
When is 'Timestamp' and 'Timestamp Reply' are used in ICMP protocol?
The usual ping command uses ECHO REQUEST and ECHO REPLY, as you've seen. It does indeed locally keep track of sent time and matches with the incoming reply to determine the round trip time.
...
- 16.1k
8
votes
Accepted
What are neighboring ports?
Most basic example of neighbor ports would be as you mentioned: "ports on two different switches (or routers) that are connected by a cable"
You won't find a defined definition for this phrase ...
- 1,491
8
votes
Accepted
Is a datagram from an upper network layer converted 1:1 to one of the lower layer?
A single TCP segment is always converted to a single IP packet by adding IP header, which is in turn converted to a single Ethernet
frame by adding Ethernet header (and footer). In other word, a
...
- 98.3k
7
votes
Accepted
Accessing devices on different subnets using a switch
Now I can commonly deduce that both the devices are part of the 192.168.0.0/16 network. Is that a correct assumption.
No, that's incorrect. You're using netmask 255.255.255.0, so that are two ...
- 17k
7
votes
Need of routers and IP addresses
Imagine you are connected to a bridge with 3 ports. One port is connected to your host; one connects to networks to the west of you, and the last one connects to networks to the east of you.
Now ...
- 66.9k
7
votes
VXLAN vs VLAN over layer 3
As you've already stated, VXLAN is L2 tunneling over IP. It's a solution to use any L3 network for creating a L2 segment.
While this is also possible with other protcols, VXLAN doesn't require ...
- 81.5k
7
votes
Accepted
Is there a Layer 2 address advertising protocol?
LLDP is not a layer 2 equivalent of RIP.
RIP is a routing protocol, advertising routes between routers.
LLDP is a device discovery protocol, so neighboring devices can learn about each other.
...
- 66.9k
7
votes
Accepted
Leaf-Spine network without routing
do I need a router (or l3) since everything is on the same network and the network is flat
Technically, no - if all nodes reside in that flat network.
However, such a large subnet is not good ...
- 81.5k
7
votes
Accepted
Why is default gateway in routers configuration usually set as an IP address?
why not just ... a MAC address?
A router might not use a MAC address on an interface - not all L2 protocols use MACs even though many do (mainly the IEEE ones like Ethernet or 802.11). Also, routers ...
- 81.5k
7
votes
How do I know the switch is layer 2 or layer 3?
In addition to @Zac67 answer, in the Catalyst product line, layer 3 capabilities are often unlocked by licenses.
So a given switch can be layer 3 capable but, depending on the installed license, may ...
- 19.4k
Only top scored, non community-wiki answers of a minimum length are eligible