Questions tagged [switching]

For questions related to traffic switching and troubleshooting the traffic switching process.

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15
votes
4answers
5k views

Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?

I know the CAM table in a switch holds MAC addresses and the ports that are associated with the respective MAC addresses. There are no such thing as CAM addresses from my knowledge, so why is it ...
14
votes
2answers
9k views

ASICs vs x86 general-purpose routing/switching

SysAdmins often try to convince me that x86 general-purpose OS's can perform just as well as routers with low MHz CPUs and dedicated silicon (i.e., ASICs) at 1Gbps line rates. This thinking is ...
13
votes
4answers
16k views

MTU and Fragmentation

Consider the following: NAS with 10G interface connected to 10G interface on switch. Client computers connected to switch via gigabit Ethernet. Will there be any gain in performance if MTU size is ...
11
votes
2answers
76k views

Port mirroring on an HP Switch (HP 2915-8G)

for sniffing purposes I need to mirror traffic on an HP 2915. How would I go about doing so?
11
votes
2answers
1k views

How did I break (half of) my network?

I'm looking for some post-event advice so this event doesn't happen again. We have a network core of two Cisco 4500x switches, configured for VSS redundancy. From those, we have iSCSI devices, our ...
10
votes
2answers
1k views

Can a switch that does NOT support VLAN capability be considered a managed switch if it has other features?

So the question is in the title. If a switch does not support Virtual Local Area Network capabilities can it still be considered a managed switch? What other features should it have to be considered ...
10
votes
2answers
12k views

Does the source MAC address of a frame change when it passes through several switches?

If PC1 sends an Ethernet frame to Switch1 which forwards the frame to Switch2 which in turn forwards the frame to PC2, does any decapsulation happen that changes the source MAC address?
10
votes
1answer
10k views

RIB vs FIB differences?

Can someone explain the differences between a RIB and FIB a little further? I didn't see any similar questions on the site so I thought this would be a good addition. The RIB routes and the FIB ...
9
votes
3answers
429 views

10 Gb blade question

I am debating with a colleague about a potential configuration. We are implementing a new blade solution that has a built in 10 Gb switch and two blade servers, each having 4 10 Gb NICs. However, the ...
9
votes
1answer
2k views

Problems Connecting Catalyst 2960G to Netgear Prosafe Via Fibre

I've got a catalyst 2960G, connected to a Netgear Prosafe GS718T switch (cheap manageable switch). Idea is I have a couple of users that need access to a test environment - hence the cheap switch. It'...
8
votes
3answers
2k views

Is there a performance difference between a managed an unmanaged network switch?

Is there a tangible difference in speed/latency between a managed and unmanaged network switch?
8
votes
2answers
101 views

Will STP lose data whilst switching from a failed link?

In a network with a dual-redundant link between two switches, will any data be lost during the switchover from an active link to the blocked link when the active link fails?
8
votes
4answers
8k views

How do I set up a VLAN between an ESXi VM and Physical Hardware?

First of all, I am a total noob. The extent of my VLAN experience is setting up a guest network on a wireless router. I have recently gotten a request to set up a public network requiring filtering ...
8
votes
3answers
770 views

Placement of firewall for VPN RA and L2L tunnels

For Remote Access (RA) and LAN-to-LAN (L2L) VPN, I currently operate a pair of Cisco VPN 3005 Concentrators tied to Internet edge routers on the outside and the inside tied to an internal pair of PIX ...
7
votes
3answers
4k views

Does a switch understand packets? If yes, what is the frame terminology for?

I was a little confused between packet and frame. The confusion was based on, if a switch is a layer 2 device, how does it reads a packet from a layer 3 device, and where is the 'frame' thing which is ...
6
votes
3answers
766 views

Does a switch always get a MAC address from a PC?

I was wondering if there is a possibility that a switch won't get the needed MAC address to it's CAM. For example, if the used protocol is UDP, where the sender doesn't need an answer back from the ...
6
votes
2answers
1k views

802.3x ethernet flow-control on user ports?

What is the best practice for putting 802.3x flowcontrol on a userport and does this inhibit performance if the application/system isn't designed for it? Eg) interface gig0/1 flowcontrol receive [...
6
votes
2answers
6k views

Should I disable STP on my access ports?

I'm going to replace some old "central" access switches to some Cisco Catalyst 2960X, and I'm not sure what to do on their STP configurations. For this network, we have some "central" access switches,...
6
votes
4answers
32k views

What OSI layer do Access Points operate on?

I am studying for CCNA. In my book I read that wireless access points belong to OSI layer 2. I did some research and I found that is correct. This raised lots of questions in my head so I hope I don't ...
6
votes
4answers
8k views

Switch Lookup Table

I was just reading a book called HeadFirst Networking and I'm a bit confused about something. I am attaching an image from the book. The page says that the direction of the frames as maintained in the ...
6
votes
2answers
721 views

Posible to connect VLAN switch through dumb switch?

Is it possible to connect a VLAN switch into a dumb switch ? The router will know how to reach network connected by a VLAN through the dumb switch please ? No edge effect ? By example, a schema of ...
6
votes
1answer
1k views

Successful Auto/Auto PAgP Port Channel?

Cisco documentation states the following on forming channels: SW1 SW2 ---------------------------------------- On On = Yes Auto/Desirable Desirable ...
6
votes
2answers
9k views

What do input discards on switch ports indicate and how can one track down their cause?

The conditions under which a switch will discard outbound packets on particular ports are fairly well established in many basic training materials, including those for CCNA. However, input discards ...
5
votes
4answers
3k views

Juniper Switching - Cheap Lab

A little bit new to Juniper here. I am working on scripting few of our switch ports. All switches are Juniper, Ex, FX, QFX, ...etc. I have no access to a lab to test my scripts, and was looking for ...
5
votes
3answers
9k views

Packet forwarding in TCP vs UDP

Recently I had a discussion about differences between TCP and UDP, and the other person insisted that there's a difference in packet forwarding: The packets in a TCP connection follow an established ...
5
votes
2answers
8k views

Why each and every single port on Layer 2 switches need to have it's own MAC address?

A switch doesn't alter the frame, and source/destination mac addresses remain how sending host specified them,so let me say it again Layer 2 Switching never changes the frames means no changes in MAC ...
5
votes
3answers
405 views

Why use 'switching' term for packet switching

On a packet switching network, a router is required to route packets to different networks. Why does packet switching uses the term 'switching' when a packet is a term for a layer 3 PDU and ...
5
votes
1answer
196 views

Cisco Catalyst Line Cards - memory considerations

Do the Catalyst Line Cards (4500 and 6500 series) hold memory (kept after reload), or some other information independently of the Supervisor Card? I ask regarding a chassis reset process, in order to ...
5
votes
2answers
76 views

Network Ten LTE Hubs Into One Network

I'm working through a tricky situation getting a field office set up out in a very rural area. There are ten 12' x 60' trailers being set up (2-3 metres apart from one another), each with varying ...
5
votes
1answer
631 views

Router benefits in 2018 compared to a L3 Switch

What are the benefits nowadays to use a Router instead of a L3 Switch ?
5
votes
2answers
3k views

Does a switch MAC address table sync across all switches in the same VLAN?

Ok, I have read up about this 16K limit for the MAC address table, or better known as the CAM table, on certain switches. Lets say I have 14 different edge switches with that 16K limit, and I have ...
5
votes
3answers
232 views

Learning switches and routers

I'm taking a computer networking course and i struggle to get to flow of things when it comes to learning switches and routers. Lets say we have a AS with LANs that connected with switches, and there ...
5
votes
1answer
1k views

Which switch MAC addresses are used for the Bridge ID in STP?

Lets imagine that I have big LAN environment with many switches and many VLANs, for example, VLANs 5,15 and 50. I have PVST+ activated, and all of my switches have same (STP) priority. I connect a ...
5
votes
2answers
3k views

Switch Buffer Sizing

What is the relationship between a switches buffer size and the effect it has on latency? I am aware of the bufferbloat issue and understand that buffers that are too large in networks of slower BW (i....
5
votes
3answers
1k views

Extending VLANs to other switches

I am working in an inherited environment where I have basically been thrown in feet first. I'm also brand new to VLANs, and only set it up via documentation from other techs in my company. After ...
5
votes
1answer
620 views

cisco route-map using details

I can't understand some details of route-map working. Example: on interface vlan_A I use route-map_A, on interface vlan_B - route-map_B. When host from vlan_A send packet to host from vlan_B what ...
5
votes
1answer
759 views

What happens when you stop receiving BPDUs with no L1 loss?

We have a redundant path for some of our communications through a.) a Metro-E provider and b.) two routers forming an L2TPV3 tunnel. We have Cisco 2960 switches at both ends running RSTP to prevent ...
5
votes
1answer
1k views

Is it possible for a private VLAN to have two simultaneous SVI mappings?

In our environment, we run our computers inline with Cisco IP phones to our switch. The problem is that our phones are on a separate VLAN from our normal access traffic. I would like to know if it is ...
5
votes
1answer
1k views

Do Full MVNO's need S-GW in their LTE network?

Presently I am analysing the LTE network architecture for a full MVNO network. I am just wondering whether S-GW is required as part of MVNO LTE architecture or MNO - SGW will be able to communicate ...
4
votes
3answers
371 views

Is there any reason to use a hub over a switch?

Given that hubs are essentially the same as switches, as far as I know, except they share bandwidth between all connected devices, while switches do not, resulting in faster connections. I am simply ...
4
votes
1answer
622 views

MAC Address learning process

Does a switch learns hosts mac address in these following scenarios: Switch port configured as access and frames received tagged on different VLAN Switch port configured as trunk and frames received ...
4
votes
2answers
297 views

Network Redundancy with LACP Trunking

I would like to set up a redundant link between two switches. I have four ports available to accomplish this. Scenario A: Switch 1 has ports 1+2 trunked together via LACP. They are plugged into ...
4
votes
1answer
3k views

What's use of Port Isolation vs traditional VLANs?

I've seen several switch products advertising port isolation feature as "way to limit ports communication without configuring VLANs" and it sounds quite... sketchy? If i understand it correctly port ...
4
votes
1answer
18k views

What are FPC and Linecards?

I am new to networking terms like this. Can somebody explain the difference between Linecards and FPCs? Are they the same or different? I have been hearing these in multiple contexts and sometimes ...
4
votes
1answer
76 views

Why switch has records in mac-table when i just set ip address to the hosts which connected to the switch?

I created a new switch and connected to two hosts in GNS3.Like this: Host1--->LS<---Host2, i think the mac-table in the switch should be empty before i sent data between two hosts. But when i just ...
4
votes
3answers
671 views

Theoretical: Bottleneck in a switch stacking environment

Quick question regarding stacking environments and their limitations regarding traffic bottlenecks. Assuming the following use case: We have a stack of 8 switchs, forming a Half 10Gbps stack ring. ...
4
votes
2answers
2k views

What is native vlan tagging?

I researched a lot of native VLAN tagging resources, but I still don't understand what is the difference with VLAN tagging. Can anyone explain it simply?
4
votes
1answer
75 views

Same Vlan Name / ID on different switches network subnet same or different?

I have several switches (some on same floor and another on other floors) all connected to core layer 3 switches through trunk links. One of the vlan id / name is repeated along the switches. May I ...
4
votes
1answer
205 views

Cross datacenter IP failover/migration

I am trying to wrap my head around this (very) simple issue of IP failover from one physical location to another. I have a few Virtual machines running at Site A where I need to rebuild the NAS. In ...
4
votes
1answer
368 views

QoS Policing vs Shaping, why policing

Regarding QoS, we have two modes: shaping or policing. The policing drops packets while shaping put the packets in buffer. Shaping seems to be the better solution in a general ways, so, why use ...