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Questions tagged [layer3]

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

2
votes
1answer
17 views

Understandable/Implementable explanation of CSMA p - persistent

I have been trying to understand how the CSMA P-persistent method works, but haven't been able to understand how it's implemented. I have referred to a few textbooks and other sources, but all of them ...
0
votes
0answers
13 views

DHCP Layer 2 and Layer 3 [duplicate]

I am having a difficult time to visualize the conceptions of DHCP Discover message in order to receive an IP address sends out a broadcast at both layer 2 and layer 3. Can someone care to explain? ...
0
votes
1answer
47 views

Arp Cache Timeout [closed]

I'm trying to poll the arp table from a backbone switch but i want to understand which records are up. I just want to know if there is a specific time for the switch to keep a record on the arp table ...
3
votes
2answers
75 views

Is static routing used in large networks?

I'm a beginner in networking stuff and just wondered if Static Routing has any use in large networks ? How about small ones ? In which cases we prefer to use static over dynamic routing ? I searched ...
2
votes
1answer
131 views

MAC Table vs ARP

I understand that for a switch to learn a MAC address, if host A wanted to send data to Host B the switch learns host A MAC and places it in the MAC table. If it doesn't know where the MAC (for Host B)...
1
vote
1answer
110 views

Successful Intervlan Routing on a Layer 3 Switch, Unsuccessful IP Routing

Hello and thank you in advance for your help! I'm using Packet Tracer for testing purposes and I' m trying to implement a simple intervlan routing in a Layer 3 Switch (3560-24PS) and an IP Routing. ...
3
votes
3answers
124 views

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 ...
2
votes
3answers
452 views

Does a router send frames or packets?

Perhaps it's a novice question, but does a router send/receive frames? When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in ...
2
votes
2answers
112 views

Mgmt Vlan vs other SVI s

Think of a layer 3 switch. Assume that we have a management vlan and a mgmt vlan interface. And we have other svi's on the switch. The question is this. I know that mgmt vlan is for telnet/ssh, simply ...
3
votes
1answer
180 views

Cisco ARP cache rewrites?

I know that the Cisco's default ARP entry expiration is 240 minutes, however how does the ARP table mechanism work when a different MAC address is seen using the same IP? In other words, if I move ...
2
votes
1answer
48 views

Is it worth the effort to split up in layer 3 with point to point links? [closed]

I have this technical question. With my family we have a little business. I got to provide internet access to three places, separated a few hundred meters each other. I need to allow to watch the ...
1
vote
1answer
38 views

HP 2920 Routing

I am working on setting up routing on a HP 2920 to a firewall. I can not figure out what I need to do to get this set up. I know that the ip routing command turns on routing and the ip route ...
1
vote
2answers
30 views

How can subnets not fulfil symmetric property?

While studying Internet Protocol, I came upon the following example of two devices: Device A: IP address: 10.1.1.1 Subnet mask: 255.255.255.0 and Device B: IP address 10.1.1.200 Subnet mask 255....
1
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1answer
242 views

Firewall on a stick for Intranet and static routing

I have a question about possible problems that can occur with this network design. If I have an intranet with a firewall on a stick design, multiple switches with layer 2+, is this setup fine? or ...
1
vote
1answer
155 views

Help with small office setup - Cisco SG350 28 port switch

I have very limited knowledge in Cisco IOS but in a crucial state to setup up a small office network. I have bought 2 Cisco SG350 28 port Layer 3 switch, Switches should be enabled with VLAN and VTP. ...
3
votes
2answers
270 views

L2 / L3 on CISCO ASR

I am new to CISCO and have the following problem: I have 3 routers. Between these only one physical connection. The VLAN 100 is connected to R1 and R2. The VLAN 200 is connected to R1, R2 and R3. The ...
2
votes
1answer
149 views

Connect two VLANs on an NE1032 Lenovo L3 Switch

I just got a new Lenovo ThinkSwitch NE1032 with some 1G sfp. I have already created two VLANs called FE and BE that have the following IDs: 2,3. I have managed to assign an IP subnet to both of them, ...
4
votes
1answer
326 views

Cisco 3172 asks for LAN_ENTERPRISE_SERVICES_PKG license to enable OSPF and PIM when they are LAN_BASE_SERVICES_PKG license features

I have several Nexus 3100 switches in which I use OSPF and PIM. Cisco says that these features are included in the LAN_BASE_SERVICES_PKG which is included by default in the switches. Switch1# sh ...
5
votes
4answers
1k views

Do layer 3 protocols use layer 2 protocols?

I saw the STP on layer 2. The guy that made the tutorial says at the end : Even though it seems that Layer 2 access layer solutions are slowly being replaced by blazing fast Layer 3 solutions. ...
1
vote
2answers
177 views

Inter vlan routing not working

Apologies if any details not clear as I'm not a network expert. I have a Procurve 3500yl layer-3 switch. I am trying to make two VLANs and get a PC in one VLAN to connect to the other VLAN. Below is ...
2
votes
1answer
187 views

Is There an Indication in Protocol Stack showing that the End Host is Mobile?

Suppose you are using the Web from your mobile phone. Is there any indication in the internet backbone, when you look at the traffic that shows that the end host is a mobile device? I am sure there ...
1
vote
1answer
37 views

Unable to reach a device on another net while having routes

I'm not sure what I'm doing wrong and would therefore need some guidance. The goal is to be able to have a SSH connection between: PC -> C On PC I have created a route route add 192.168.50.0 mask ...
2
votes
1answer
91 views

TCP connection question

Let’s say I have 4 ethernet interfaces getting IP addresses via DHCP. I make a TCP connection to a TCP server via one of the IP addresses on a certain ethernet interface. After the connection is ...
1
vote
2answers
261 views

BGP with x2 sessions and x2 L3 VLANs - Please Explain

I am learning about Cisco BGP networking now and came across an interesting situation. In my examples, there was one which suggested that two VLANs were configured on Layer 3 in order to run two BGP ...
1
vote
3answers
114 views

Why do clients request a MAC via ARP, if the router knows the local LAN's MAC addresses already?

If I have an infrastructure type network, why does a local PC send out an ARP request for a MAC? Doesn't the router know the MAC addresses already, since it is using at least Layer 2? Does it do ...
1
vote
2answers
155 views

Routing specific TCP/UDP packets from VLAN's to proxy server

I need to set up a solution which is for routing specific TCP/UDP packets between the devices in two separate VLANs through a proxy server. For eg: all my computers are connected to one VLAN(1) and my ...
2
votes
2answers
625 views

Connecting Layer 2 switchport to layer 3 port

I have a config that I am trying to bring up, and in my mind it should work, but perhaps I am missing something. The idea is that one end of the link is a layer 3 interface on a router. The other end ...
1
vote
1answer
34 views

Separate network for test systems

I often read that you should put customer machines into a separate (testing) network like a DMZ. Is a layer 3 device (switch/router + firewall) a good option for this? Since some ports need to be ...
3
votes
5answers
441 views

Is there a Layer 2 address advertising protocol?

I needed help in understanding if LLDP/CDP is the Layer 2 equivalent to RIP or say any Layer 3 route advertising protocol. If not,is there a protocol that advertises the MAC Address Tables among ...
1
vote
1answer
364 views

Routing and Bridging on a Layer 2 or Layer 3 device

The thing that intrigues me is, say I have a router and I configure it’s interface as a Layer 2 and have 2 Vlans on the same router. So if I want to transfer the data from one Vlan(say VLAN-10) to ...
0
votes
1answer
54 views

Routers and RIP violation of isolation?

I'm studying networking from the book 'A top down approach' from Kurose and Ross. In the book it is stated that routers are generally considered Layer 3 devices (i.e. implementing the stack up to ...
2
votes
1answer
736 views

At which layer does router operate?

I have studied from various sources that router is a layer 3 device. It does routing based on Network layer (layer 3) header, but I have a doubt. Network address translation (NAT) is a feature of ...
4
votes
1answer
74 views

How does Junos distinguish that route is learned in Layer 3 or Layer 2 VPN environment?

As I understand from Understanding Junos OS Routing Tables document, then bgp.l3vpn.0/bgp.l3vpn-inet6.0 or bgp.l2vpn.0 tables contain routes learned from other PE routers in Layer 3 or Layer 2 VPN ...
2
votes
1answer
125 views

Weird networking behavior with a gateway between a switch and CMC module, on Dell VRTX equipment. Am I doing something wrong?

Diagram: Here's the simplest way I know how to explain how the internal networking of this Dell VRTX works. So, you have your 4 blades and your network switch module that have integrated remote ...
5
votes
3answers
11k 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 ...
1
vote
1answer
473 views

Bridging networks without NAT: how it's done?

I have quite limited networking experience, so probably i'm asking about very simple things. I'm reading about linux bridge interfaces, and documentation states that there is no NAT by default and ...
1
vote
2answers
109 views

1 Layer 3 Switch, 2 Vlans, 2 Subnets, and an Unmanaged Switch

Is it possible to for a device with the ip address 192.168.0.1 and Vlan 100 to communicate with an other device with the ip address 192.168.1.1 and Vlan 200 with the following architectures Senario 1:...
2
votes
3answers
2k views

When is 'Timestamp' and 'Timestamp Reply' are used in ICMP protocol?

I started the packet capture in my laptop through Wireshark application. Now through cmd, I pinged some server (say, www.google.com). And i stopped packet capture and analysed the packets being ...
2
votes
2answers
272 views

Routing steps on a serial port

"Because the exit interface is not an Ethernet network, R2 does not have to resolve the next-hop IPv4 address with a destination MAC address." - this is routing from serial port , can anyone explain ...
0
votes
1answer
441 views

how to do intervlan routing between two hosts in different subnet

how to do intervlan routing between two hosts in different subnet separated by two layer 3 switches & without using ip routing command & by using the concept of native vlan.
3
votes
3answers
290 views

Layer 3 tunnel with Dynamic IP address

I want to ask whether it is possible to configure Layer 3 Tunnel with the two end points/interfaces have dynamic IP address? If the interface IP change, the tunnel will have to be re-negotiated, is ...
5
votes
5answers
1k views

Why can't two hosts (in two different logical networks) connected to each other through cross-over cable communicate?

Let us say, i have two computers (hosts) A and B. Where A has been assigned an IP address of 192.168.1.10/24 and host B has been assigned an IP address of 192.168.2.11/24. And both of them has been ...
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1answer
425 views

How to implement Layer 3 (OSPF, IS-IS) link redundancy?

I think this kind of topic may be a course basic, but I'm still have a lot of technical doubts on how to implement redundant links on Layer 3, for example: -In order to use dual homing for a remote ...
2
votes
1answer
596 views

SD-WAN vs MPLS VPN

Citing wikipedia on MPLS VPN There are three types of MPLS VPNs deployed in networks today: 1. Point-to-point (Pseudowire) 2. Layer 2 (VPLS) 3. Layer 3 (VPRN) I am confused about the difference ...
1
vote
2answers
197 views

CGN and its advantages

I have been reading about CGN. Though similar to NAT it is used by service providers to route traffic without the need for the a public IP address. But when the packet leaves the ISP to the public ...
1
vote
1answer
147 views

Two Layer 3 Switches to one router

So I have a cisco 2811 router and 2 3560 switches Currently the router is connected to Core1 only, what i would like to do is use the other port on the router (fa0/1) to connect to Core 2. How do I ...
1
vote
1answer
41 views

Catalyst InterVLAN Routing w/ Failover ASAs

I currently have interVLAN routing configured on my Catalyst 3750. My gateway of last resort is my ASA firewall. The switch reaches the firewall through a layer 3 port. The port is configured as ...
4
votes
3answers
652 views

How does a router a layer 3 device translate port address in PAT, as it is a layer 3 device?

While I was reading about PAT i.e Port Address Translation.The router was configured to translate all the private IP addresses to one single public IP.Since router is a layer-3 device, it can do that ...
3
votes
2answers
4k views

How to trunk VLANs over Layer 3 EtherChannel?

I am trying to setup a network that includes an EtherChannel link between two Cisco Layer 3 switches (Catalyst 3750). I am using a collapsed core hierarchical network. The picture above is my ...
2
votes
1answer
268 views

INTER-VLAN Routing with different Internet Access for each vlan

I have a situation that needs some clarification. I have three sites (1,2,3). The core switch do Inter-vlan routing. Site 1 and 2 must access the internet via ISP1, while site 3 will access internet ...