Questions tagged [layer3]

For questions about the OSI layer-3 (network layer).

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5answers
380 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 ...
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3answers
3k views

Juniper EX how to clear route forwarding table?

After layer 3 routing a large IPv6 assignment on an EX Juniper switch, the route forwarding table filled up and some entries corrupted or became otherwise invalid. We want to clear the whole table. ...
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2answers
58 views

Connecting switches together

I have L2 switches which will be daisy chained together (yes I know, daisy chaining isn't great, but anyway..) The L2 switches will then link to a L3 switch. Both the L2 and L3 switches have x4 10GbE ...
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2answers
45 views

Why is in all arp table snmp oids an interface index before the ip number?

When I want to get arp information about a single ip number or subnet, I have to snmpwalk the whole arp table, as some oid architects had the "great" idea to always insert an interface index ...
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4answers
34k views

Access Multiple VLANs from One Computer

I inherited a bit of mess and am preparing to redo our IP addressing scheme and also split our network into multiple VLANs. Possibly something like: 10.1.10.0/24 VLAN 10 VOIP 10.1.20.0/24 VLAN 20 ...
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4answers
26k views

What layer of the OSI model does NAT work?

Simple question and the answer is layer 3 of course, but can we say that PAT is working on layer 4 also because it deals with port numbers which is a layer 4 function? Or is it only a layer 3 ...
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1answer
29 views

When traffic is intiàted from pc is ANDing process or ARP process start working first

When traffic is initiated from desktop which process starts first; the ARP process or ANDing process?
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1answer
143 views

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 ...
2
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1answer
169 views

Where exactly is the limited broadcast address used?

I read that limited broadcast address will be dropped by the router. So, it's not used in the layer-3 (Network layer), where IP addresses are meant to be used. So, where exactly is it used?
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3answers
97 views

Minimum MTU size on Ethernet and minimum Ethernet frame size

I am a bit confused about the understanding of the relationship between minimum MTU of MTU and minimum Ethernet frame size. We know that the maximum MTU of Ethernet is 1500 Bytes which makes the ...
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2answers
155 views

What is the advantage of Supervised Machine Learning over Deep Packet Inspection in Network Traffic Classification?

As per the definition of Deep Packet Inspection (DPI), it uses signatures for packet filtering. Supervised Machine Learning can help put a label on a packet which does not get identified by Deep ...
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3answers
1k views

Difference between router leg and static routes

I am looking a L2/L3 switch spec. which says it supports 256 Router Legs and maximum of 32 Static routes. Can somebody explain with an example, what is the difference between router leg and static ...
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2answers
44 views

Layer 2 managed switch and layer 3 switch

If you have layer 2 managed switches which have VLAN's on them, do you still need a layer 3 switch/router?
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2answers
27 views

What is the need for the NEXT HOP coloumn in the routing table when we already mention the OUTGOING INTERFACE in another coloumn?

If the OUTGOING INTERFACE is already mentioned in the routing table, it is natural that the next hop will necessarily be the router attached to the outgoing interface. Then why is there a separate ...
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0answers
25 views

network cutover for remote site from L2 to L3 over IPSec tunnel

I have been trying to cutover one of our remote sites (A) to the new ISP we have purchased. The existing setup is utilizing L2 through another remote site (B) and coming back to the main campus. The ...
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2answers
77 views

Are all packets addressed with the MAC address of the router as they leave the machine?

In the Comptia Network+ All in One, it is said that most home routers have a switch built into them. It is also said that the first thing the router does is strip off any layer two information present ...
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0answers
13 views

Basic Subletting 10.239.142.216/11 [duplicate]

First time poster (kindly don't eat me alive) i was using https://subnetipv4.com/ to acid test my subletting skill i got 9/10 correct this is the chosen one that broke my streak as you can see i ...
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2answers
55 views

Can Northbound interfaces (REST API) in a Software Defined Network (SDN) be used to manipulate QoS parameters?

I am working on a project involving Quality of Service (QoS) manipulation in Software Defined Networks (SDNs). I know that the following parameters affect the QoS in an SDN: Time information (inter-...
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1answer
54 views

Why does the Layer 3 switch drop the ping packet?

I am trying to ping from PC2 (not PC1, there's typo in the picture) to the router's int g0/0, but the packet is dropped at the L3 switch which is along the path. I have tried setting a default static ...
2
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1answer
70 views

what were the classless routing protocols used with VLSM when it was first introduced?

Since VSLM is supported only by classless routing protocols, if VSLM was introduced in 1987(RFC 1009) and all classless protocol(RIPv2 developed in 1993 , OSPF standardized in 1989 RFC 1131 ) cited ...
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2answers
82 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 ...
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4answers
17k views

Inter VLAN routing working, but VLANs can't access Internet

i have a question/problem. i have a local router with default-gateway 192.168.3.254, now on my layer 3 switch 3560 i configure 3 vlans. vlan 10 - data /ip address 192.168.10.254 255.255.255.0 vlan ...
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0answers
14 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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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 ...
2
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3answers
9k views

How to assign a static IP to a Cisco Layer 3 switch in order to connect using SSH?

The steps of this manual have been executed in order to configure SSH. Once SSH has been configured, how to access the switch from a computer using SSH? The following steps have been executed in ...
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2answers
54 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
56 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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3answers
204 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 ...
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6answers
20k 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
91 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. ...
2
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1answer
87 views

Why Classful addressing is not in use if we can subnet them?

So, Let's think that organization needs 5000 IP addresses. Giving 20 C Class IP addresses will cause of adding 20 entries for ISP router. That's problem. We could give Class B IP address, but that ...
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3answers
12k 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)?
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2answers
6k views

Pinging a different vlan without routing

I have a layer 3 switch with two vlans 10 and 20. This is the only configuration i made on the switch: Switch(config)#vlan 10 Switch(config-vlan)#name IT Switch(config-vlan)#vlan 20 Switch(config-...
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2answers
2k views

What is the proper switch configuration for the switch that is connected directly to ISP source?

The Question: What is the proper configuration for the L3 switch to be allowed to assign public IPs for the firewalls? I guess All I need is that the switch L3 act as a layer 2 switch...Right? ...
2
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1answer
54 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
748 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 ...
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1answer
36 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
101 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 ...
0
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1answer
122 views

Unable to ping between router and routed port on L3 switch. Why?

I've got an old Cisco 2811 connected to an old Cisco 4948 L3 Switch. I'm trying to teach myself a little more about L3 Switch implementation. All I'm trying to do at this point is get the router and ...
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1answer
52 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
101 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 <----...
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2answers
111 views

Unicast to Multicast possible?

could I check if it is possible to convert TCP traffic to UDP multicast and if there are any appliances / switches that can do so? E.g. Workstations A, B and C establishes a TCP connection with ...
4
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2answers
474 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 ...
2
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2answers
481 views

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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4answers
44k views

What are the reasons for seeing an incomplete ARP?

As was mentioned in this post: The reason for seeing an incomplete ARP is that "An ARP request was sent for that address, but the host with that address is not up and running on the LAN, so there is ...
0
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1answer
206 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 ...
5
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5answers
346 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 ...
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1answer
70 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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1answer
560 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 ...
4
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3answers
2k views

How does Deep Packet Inspection work with encrypted packets?

I've been reading up on Deep Packet Inspection for Software Defined Networks. However, I know that some applications use encryption to evade Deep Packet Inspection. Is there any alternative (such as ...

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