Questions tagged [layer3]
For questions about the OSI layer-3 (network layer).
271
questions
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1answer
68 views
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 ...
1
vote
1answer
40 views
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 ...
1
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4answers
95 views
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. ...
0
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1answer
93 views
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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0answers
16 views
MPLS provider A L3VPN to MPLS provider B migration
i have a Datacenter infraestructure with a mpls of SP A, and i would like to migrate to another wan line of a different SP B. Mpls current circuit is providing L3 VPN service, one VPN per remote site. ...
0
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1answer
67 views
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 ...
0
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2answers
46 views
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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2answers
47 views
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 ...
0
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1answer
27 views
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 ...
0
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2answers
34 views
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---...
1
vote
1answer
83 views
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 ...
2
votes
1answer
120 views
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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2answers
95 views
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 ...
6
votes
2answers
1k views
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?
1
vote
2answers
55 views
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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0answers
19 views
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 ...
1
vote
2answers
65 views
Some extra clarification regarding VLANs and SVI
Good afternoon guys,
I've got a question regarding VLANs and SVIs.
First of all, I know some concepts about VLANs, and I've been in the IT field for a while.
But this one is a bit confusing for me.
...
2
votes
3answers
204 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 ...
2
votes
2answers
88 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?
0
votes
1answer
2k 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 ...
0
votes
2answers
164 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 ...
1
vote
3answers
719 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 ...
0
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2answers
74 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?
1
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2answers
36 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 ...
0
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0answers
27 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 ...
1
vote
2answers
241 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 ...
1
vote
0answers
14 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 ...
0
votes
1answer
103 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
votes
1answer
85 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 ...
1
vote
2answers
398 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 ...
0
votes
1answer
214 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. ...
0
votes
3answers
971 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 ...
2
votes
2answers
448 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. ...
3
votes
1answer
309 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 ...
2
votes
1answer
93 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 ...
1
vote
1answer
182 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 ...
4
votes
2answers
800 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
vote
2answers
176 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
votes
2answers
365 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 ...
0
votes
2answers
84 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-...
1
vote
1answer
217 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.
3
votes
1answer
181 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 <----...
0
votes
2answers
328 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 ...
0
votes
1answer
244 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 ...
4
votes
2answers
527 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
votes
1answer
223 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, ...
2
votes
2answers
302 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 ...
4
votes
3answers
3k 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 ...
0
votes
1answer
1k 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
votes
4answers
435 views
ACL on routers to block TCP/UDP ports
How routers understand the layer 4 port numbers to be blocked in ACL?
When an ACL to block TCP/UDP traffic with certain port numbers is applied on a router/L3 interface , how will router understand ...
