Questions tagged [layer3]
For questions about the OSI layer-3 (network layer).
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Can a jumbogram (giant data packet) be used at a large scale (in WAN for example)?
There are many scientific paper for Jumbo frame, even more, some real implementations and deployments. But it is not the case for Jumbogram !!
Jumbo frame (geant frame) for Layer 2; Jumbogram (geant ...
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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 ...
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Does the IP header have a "Padding" field?
I found two images of the IP header, one image shows a field called "Padding", while the other image don't show the "Padding" field:
Which one of these two images is correct?
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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)
...
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Configuring HSRP on multiple L3 devices
I am currently doing an enterprise campus network which consist of Three Tier hierarchy and a simple MPLS design.
Currently, I'm stucked at HSRP configuration on the Core Layer to the Edge Router. ...
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Routing VLANs to Firewall Ports
My network has 3 VLANs: 10, 11, 12, and their address spaces are 10.0.X.0/24 where X is the VLAN ID. Their default gateway is a virtualized pfSense (even though it's virtual, I will use terminology as ...
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Is DHCP in the application layer or the network layer?
Tanenbaum's Computer Networks says:
5.6 THE NETWORK LAYER IN THE INTERNET
...
5.6.4 Internet Control Protocols
In addition to IP, which is used for data transfer, the Internet has
several companion ...
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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 ...
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How IP packet's payload bigger than the whole former PDU (segment)? [duplicate]
As far as I know:
File is too big ---> Fourth layer (TCP or UDP) divide it to a multiple segments ---> Then each segment encapsulated separately into a packet.
What means if I have 10 segments, ...
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ICMP codes in response to ICMP traffic, not UDP/TCP
I am trying to wrap my head around a concept and I am having some trouble. If I ping 8.8.8.8, 10.8.1.1 replies to me "Destination port unreachable".
Ping uses ICMP, so it does not have a '...
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Ospf multicasting with two different group
Suppose I have one ospf network where two multicast group exists. And some routers is ospf which belongs to one group or multiple group (Like: routers E, H) and router is layer3 router (Like: ...
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Custom option in IP header
I would like to add (or piggyback on an existing not used) a custom option to the IP header. I've full control of the IP stack at both end points, but I've no control on all the hops in the route (...
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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-...
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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 ...
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Actually ICMP message makes layer3 reliable?
We know that ICMP is connectionless because it does not require hosts to handshake before establishing a connection.
But when packets gets dropped in between route then respective router informs the ...
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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 ...
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Time taken to complete a routing table update and possible interruption
I am wondering if a routing/forwarding table update at a switching node (e.x., a switch or layer-3 router) can cause momentary packet drop or increased delay for a data stream that will traverse this ...
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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....
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Which ranges of IPv6 and IPv4 do requests to the local network and the host?
I'm looking for the range of IP address that is bound to the local network or the host itself.
So far for IPv4 I found:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255....
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Does a Transparent Firewall need a Default gateway if directly connected to a layer 3 device that is actively performing routing?
Good folks of the Network Engineering stack!
I have a question that I assume most people could answer in their sleep. To better illustrate my question, I've provided a sketch of my network below.
In ...
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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 ...
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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 ...
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Does a gateway always have to be on the same subnet as the host IP address? [closed]
The obvious answer is yes, I suppose, but my VPS provider doesn't seem to agree.
I've just uploaded a Ubuntu 20.04 instance, and the provider is telling me:
IP address: 77.xxx.yyy.zzz/32
Gateway: 10....
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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 ...
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Could we use private IP address as directed broadcast address?
We know that private IP addresses ranges of class A, class B, class C are 10.0.0.0-10.0.0.255, 172.16.0.0-172.16.255.255, 192.168.0.0-192.168.255.255 respectively.
My first questions is that first and ...
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Layer 3 switch as access switch
Is it possible to have Layer 3 switches at access level (meaning the PCs are connected to it) if multiple VLANs are spread out accross multiple switches? For example, VLAN 10 is present at SW1 and SW2....
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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 ...
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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 ...
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What is the minimum MTU of IPv4 68 bytes or 576 bytes?
I read that 68 bytes is the minimum size of IPv4 datagram every device must be able to forward without further fragmentation.
576 bytes is the minimum size of IPv4 datagram every device has to be able ...
user80210
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Why the two connected routers via PPP doesn't use ARP but ethernet use 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, ...
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Why does OSPF use flooding despite using multicast?
We know that flooding is only possible in layer2 switch. But in OSPF router in layer3 uses flooding with multicasting. Suppose we have one router in OSPF uses multicast address 225.0.0.9. If router ...
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How in Distance vector routing one router communicates adjacent router through broadcast address and OSPF uses unicast with another?
In distance vector routing algorithm one router can communicates(shared the routing table) with adjacent router by broadcasting message which are in same subnet. OSPF uses flooding to unicast message ...
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Are IPv4 type of service and IPv6 traffic class equivalent to each other or is traffic class IPv6 specific? [duplicate]
IPv6 has a traffic class field. According to the specification it is an IPv6 length, out of which first 6 bits are called code point or differential services code point (DSCP) and the last 2 bits are ...
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How UDP checksum get IP address to make pseudo header in transport layer?
We know that UDP checksum's pseudo header contains the most important parts of the IP header, that is, source and destination address, protocol number and data length.
I hope that the concept of IP ...
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Why router can't be used for converting different model of network but gateway can do this?
We know that Router can't be used for converting different model (e.g OSI model to TCP/IP or TCP/IP model to OSI) of network. It isn't a multiprotocol converter. But gateway is a highly sophisticated ...
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Does a router have multiple DLLs inside?
I came across a practice question of true/false answer type . The statement is:
"A router has single network layer that will interact with 2 Data link layers" .
Ans:True
(no explanation ...
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How Pruning avoids loops in Protocol Independent Mulitcast (PIM- SM)?
I can not think of a scenario, how pruning avoid loops in PIM-SM when a router joins a SPT. I understood that it avoids duplicate messages, but how it avoids loops?
I want a scenario where the router ...
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If router is a layer 3 device how can it have an application interface (GUI)?
It is said that layer 3 devices such as routers do not have an application layer. But whenever I want to configure my home router I punch in the IP address and open up its graphical user interface. ...
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Cannot Create Subinterface on C3650 L3 Switch
We have WS-C3650-24TS Catalyst L3 switch. I am trying to create a sub-interface on the ports but cannot make it work as the following error shows. Is there something I'm missing?
Sorry, newbie here.
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ICMP packets are being dropped while pinging
I am pinging from one of the Juniper L3 interfaces to another with a rapid ping count of 10000 packets. It's a direct 100G optical connection and I am seeing 10-15 packets being dropped by the end of ...
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How to configure static routing when there are two routers between the source and destination network?
How can i perform static routing from router A to reach 192.168.1.0/30 network in the below diagram(please don't ask why do i need two routers between them).
All the example of static routing i have ...
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Proxy-ARP when the destination device is connected to the same layer-2 switch, but belongs to a different subnet
I have recently learned about Proxy-ARP and am slightly confused about what would happen in the following scenario. Let's say I have two host devices A (IP: 10.0.0.10/24) and B (IP: 10.0.1.10/24) that ...
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Routing switches at core and distribution
My employer has your standard 3 layer architecture, however they want both core and distribution routing and switching.
This is so that some networks are routed, and some use only layer 2 between ...
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Tagging a Vlan across routers
I'm usually against tagging a VLAN across a router, as to not incur issues with spanning tree.
My company is asking the following
PLC --Vlan72-- SwitchA --RouterA---CoreRouter---RouterB---...
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How does Network Layer behave when client received a unicast DHCP offer?
I went through various stack exchange post to understand the concept of DHCP offer when it comes as a unicast to client from the DHCP server.
A server can send a unicast DHCP offer since it knows the ...
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What is the impact of "no switchport" with "no ip address"?
I've a monitoring tool named Spectrum from CA Click. It automatically forms links between devices by check their configuration, and etc. Recently a change was made on my switch by a regional and the ...
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Link failure detection between 2 routers
When 2 routers are linked directly together with eBGP between them, how is a link failure detected ? With the BGP timers ? Or faster with some sort of L1 tool?
For instance, assume we have the ...
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How do I know the switch is layer 2 or layer 3?
Is it possible to find the switch is Layer3 or Layer2 in (Switch)CLI? Is there any command to check whether the switch Layer(Layer 3 or 2) in CLI?
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How does an L3 Supported Switch differentiate L2/L3 Packets?
I had a managed or layer 3 supported switch (it can process both layer 2 and layer 3 packets). Now a packet from a connected host comes to it, sending traffic. How does the switch decide to process it ...
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Switch vs. Router and sequence of OSI Model [duplicate]
As I understand it:
A switch (layer 2) seems to define a LAN and a router (layer 3) enables communication between distant LANs.
A device on a LAN will give it's MAC address to the switch upon ...
