Questions tagged [layer3]
For questions about the OSI layer-3 (network layer).
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intervlan routing with PfSense
I Need some guidance on getting my lab networking configured. Any support is appreciated.
My Lab consists of:
2 cisco switches: 2960s(access layer 2) and 3750X(ip routing/layer 3)
Xenserver with ...
CommunityBot
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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 ...
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Interpretation of the name of an ITU-T document
I'm reading a document that cites a standard called ITU-T SG 13 Q5 WG. I believe that SG 13 stands for Study Group 13 and Q5 refers to Question 5. However, I don't know what WG stands for. And most ...
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Multiple hosts with same ip/subnet seperated by router possible?
Bit of a newb question but just curious if it can be done.
Is it possible to have multiple hosts with the same ip/subnet (eg 10.101.30.10/24) each seperated by a layer 3 switch/router, where one of ...
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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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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
...
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Is it possible to assign a default gateway per routing interface on a layer 3 switch
Here is the scenario. Currently there is a flat layer 2 network with a single /24 subnet. The intent is to segment that /24 using a layer 3 switch. On the /24 network there exists clients with ...
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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 ...
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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, ...
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The use of a link local IPv6 address
In a networking course that I'm following, there was a mention of several ways of how IPv6 link local addresses can be used, such as
Assigning the link local address of a router/L3 switch as the ...
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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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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
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Packet tracer is changing my addresses ipv4
Could someone help me with this?
I have a subnet with the ip: 172.16.193.0 in the fastethernet 0/0 of my router and when I go to put it in RIP the Packet tracer is changing it for another ip:172.16.0....
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What does 'moving packets away from the source' in RPF means?
I recently started studying multicast and I am a bit confused by how reverse path forwarding is explained.
Most of the sources describe RPF as 'moving packets away from the source' but I understand ...
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The length of Fragment header in IPv6
From RFC2460 :https://www.rfc-editor.org/rfc/rfc2460#section-4.5, the length of the fragment header seems to be fixed 8 bytes.
But when I test with Scapy with the default fragment header, from sniffer ...
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Difference between routing, forwarding, and 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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Cannot get inter-VLAN routing to work
The router at the top is from the ISP and I have no control over things like WAN, NAT, etc.
Network 192.168.1.1/24 is fine, but I cannot get inter-VLAN routing between VLANs 1 and 55.
PC 1 cannot even ...
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Why hosts have routing tables?
I don't understand why hosts in a network have a routing table. Aren't all packets sent by default to the switch, and the latter determines which port to forward the packet to based on the mac address?...
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What does the network layer do at the receiver
My book (Andrew S. Tanenbaum, “Computer Networks”, Fifth Edition.) mentions while explaining the network layer that the key issue with a network layer is
determining how packets are routed from ...
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Why do transport layer do data chunking. If there is fragmentation in Network Layer
I just curiously wanted to know about the question regarding L4, L3 Data Chunks, IP Fragmentation :
Data chunking happened at Layer 4(Transport, TCP), and
Fragmentation at Layer 3(Network, ipv4)
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Is it possible to perform a Layer 2 (MAC address) traceroute?
I understand the difference between layer2 & layer3 and MAC & IP. I understand address resolution protocol, etc. But is there any way to do a traceroute that will show Layer 2 information? For ...
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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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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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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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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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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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What is the relationship between the IP address and MAC address?
I own a MAC address and I want to know from it, the IP address.
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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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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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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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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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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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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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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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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 ...
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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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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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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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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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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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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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Intervlan routing using two Layer 3 Switches in Packet Tracer
I am having trouble when I am using two Layer 3 switches and two PCs to create a simple network for Inter Vlan routing,
First of all have a look at this network,
The configuration for PC1 is,
IP: ...
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What's the difference between port number and protocol number?
Can someone explain it clearly. I know that port numbers are used by applications to differentiate which services you have requested, and routing protocols use protocol numbers in TCP header.
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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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