34
votes
Accepted
Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?
CAM (Content Addressable Memory) is memory that can be addressed by content, rather than a numeric memory address. You can look up the interface by presenting the memory with the MAC address. This is ...
- 94.6k
21
votes
Accepted
ASICs vs x86 general-purpose routing/switching
Is it correct in assuming that ASICs for router or switch interfaces will outperform the use of an x86 CPU for all packet processing which will greatly suffer from CPU interrupts?
It's hard to say ...
- 29.6k
18
votes
Accepted
Can a switch that does NOT support VLAN capability be considered a managed switch if it has other features?
Yes. A managed switch is a switch you can configure in some way or other. Whether it supports VLANs or not is not the question. Even a switch (or a hub for that matter) that only provides status ...
- 72.8k
15
votes
Accepted
Why can't devices in different subnets talk with each other?
Devices in different subnets can communicate. That is the purpose of a router. Routers route packets between different networks.
Even if devices in different networks are on the same layer-2 ...
- 94.6k
14
votes
Accepted
Does a switch understand packets? If yes, what is the frame terminology for?
You need to understand the concept of layers.
An application will send data to the Transport Layer. The Transport Layer protocol will encapsulate the data inside headers for the Transport Layer ...
- 94.6k
14
votes
Why is the CAM table in a switch called CAM table and not MAC table even though it holds MAC addresses?
CAM - Content Addressable Memory, referring to the memory used for the MAC address table.
It works kind of reverse from RAM, you address it by giving it content and it returns you the address where ...
- 1,498
14
votes
Accepted
Is there a performance difference between a managed an unmanaged network switch?
Good question. The short answer: No, there's no inherent difference in the speed or latency available to hosts talking to one another on a managed vs. unmanaged switch. In reality though, you'll ...
- 2,092
13
votes
Accepted
Does the source MAC address of a frame change when it passes through several switches?
No. If all the switches are layer-2 switches, the frames are switched without any changes.
Only with routers, including layer-3 switches where the packets need to cross to other VLANs, will the ...
- 94.6k
13
votes
Accepted
RIB vs FIB differences?
The forwarding information base (FIB) is the actual information that a routing/switching device uses to choose the interface that a given packet will use for egress. For example, the FIB might be ...
- 6,046
13
votes
Accepted
Difference between Giant Frame and Jumbo Frame
Generally, a giant frame is a frame that is too large for the receiving interface. As a malformed frame it is dropped.
A jumbo frame is a frame that is larger than the standard allows (1518 bytes for ...
- 72.8k
12
votes
Accepted
Should I disable STP on my access ports?
You really, really do not want to disable STP where you connect switches to other switches. That is the entire purpose of STP. If you disable STP, and there is a problem, it will really be too late ...
- 94.6k
12
votes
Accepted
Does a switch always get a MAC address from a PC?
A switch learns the source MAC from the sender. If the destination is not in the CAM table, the switch floods the frame out all ports. So if the receiver never responds, the switch will never learn ...
- 63.5k
12
votes
Accepted
Is there any reason to use a hub over a switch?
For the most part, no. Hubs are also known as repeaters - meaning that they basically echo whatever is coming in to a given port out all other ports in the domain. The idea is (or, more properly, ...
- 6,046
12
votes
Accepted
Does an unmanaged switch deal with IP addresses at all
An unmanaged switch doesn't use/care for/understand IP addresses at all.
A managed L2 switch uses IP addresses for management only. Some L2 switches also support limited L3/IP functionality like ACLs. ...
- 72.8k
10
votes
Packet forwarding in TCP vs UDP
Transport of both UDP and TCP packets from one router to the next is done at the IP layer and solely based on the information at this layer. This means, that there is no distinction between UDP and ...
- 2,083
10
votes
Accepted
Difference between routing, forwarding, switching
In general, forwarding refers to a device sending a datagram to the next device in the path to the destination, switching refers to moving a datagram from one interface to another within a device, and ...
- 94.6k
10
votes
Accepted
What's use of Port Isolation vs traditional VLANs?
Port isolation -also called private VLAN (thanks @Stuggi)- is a very useful feature for switches that connect end users.
In a typical network you will have many end-users computers grouped together ...
- 18.5k
10
votes
Accepted
MAC Address learning process
It depends on the manufacturer. For Cisco switches:
Switch port configured as access and frames received tagged on
different VLAN
Frame is dropped
Switch port configured as trunk and frames ...
- 63.5k
9
votes
Why each and every single port on Layer 2 switches need to have it's own MAC address?
One key use for per port MAC addresses on switches is for Spanning-tree BPDU's. These are Layer-2 multicasts with source MAC address of the egress switch port.
I would have to brush up on other ...
- 1,276
8
votes
Juniper Switching - Cheap Lab
* UPDATED Dec 2017 *
Juniper renamed this product to the vSRX (virtual SRX). You can still download a trial copy - https://www.juniper.net/uk/en/products-services/security/srx-series/vsrx/
You can ...
- 860
8
votes
Juniper Switching - Cheap Lab
The SSG-20 only runs ScreenOS, not JunOS. Juniper switches run JunOS, so this won't help you test your scripts and test configs. Personally, I'd look for a cheap 2nd hand low end model Juniper, but it ...
- 15.8k
8
votes
Accepted
Packet forwarding in TCP vs UDP
Actually there is some truth in what the other person was saying, though it is largely false.
Is it true (that packets in a TCP connection follow an established path)?
Yes, in general, all packets ...
- 277
8
votes
Accepted
Router benefits in 2018 compared to a L3 Switch
It usually comes down to options and resources, where routers have more of each. Routers often have the ability to have different types of interfaces that are not available on switches. They also ...
- 94.6k
8
votes
Posible to connect VLAN switch through dumb switch?
An unmanaged switch will only have one VLAN. Some unmanaged switches will drop tagged frames as damaged, others will strip the tag, and some will simply pass the frames unchanged. Unless you try it, ...
- 94.6k
7
votes
Why each and every single port on Layer 2 switches need to have it's own MAC address?
Okay, here is a more direct answer.
In the past implicit tagging required each port to have a MAC address. With 802.1Q, that is no longer necessary.
Transparent bridging does not alter the frame. ...
- 443
7
votes
Why use 'switching' term for packet switching
A very good question coming at it from a networking viewpoint. Your question is based on the networking models that were developed long after packet switching was proposed as a concept. However ...
- 26.8k
7
votes
Ping between different subnet across a link
No. It won't work
Let's look at PC1:
Its IP address is 10.10.10.1, its netmask is /24 or 255.255.255.0
This means that as far as it is concerned, IP addresses in the rage of 10.10.10.0 - 10.10.10....
- 456
7
votes
Will STP lose data whilst switching from a failed link?
If i remember, default spanning tree (802.1d) takes about 50 secs to reconverge. That is the duration for which you will be losing frames.
A link is detected down by the loss of 10 hello pkts. These ...
- 585
Only top scored, non community-wiki answers of a minimum length are eligible