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 ...
- 98.3k
19
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 ...
- 98.3k
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 ...
- 81.5k
15
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 ...
- 1,591
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 ...
- 98.3k
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 ...
- 2,102
14
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 ...
- 81.5k
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 ...
- 98.3k
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 ...
- 6,104
13
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, ...
- 6,104
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 ...
- 98.3k
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 ...
- 66.9k
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. ...
- 81.5k
10
votes
Accepted
Difference between routing, forwarding, and 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 ...
- 98.3k
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 ...
- 19.4k
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 ...
- 66.9k
9
votes
Accepted
How can hosts on two different VLANs communicate?
Two separate VLANs must communicate through a layer-3 device, like a router.
Devices on a VLAN communicate with each other using layer-2. Layer-3 must be used to communicate between separate layer-2 ...
- 98.3k
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 ...
- 98.3k
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, ...
- 98.3k
8
votes
Accepted
Why would a switch ever send an ARP request for a MAC address when it can just wait for the first packet to be received from a device?
You are confusing switching, where a switch creates and updates a MAC address table as frames pass through it, with the switch management.
Switching is a layer-2 function, and a dumb switch will ...
- 98.3k
8
votes
Accepted
Two switches, double connection, no LACP: how does it work?
Most likely, the rapid or the multiple spanning tree protocol RSTP/MSTP has been activated on the 1910 switch.
With the unmanaged 1410 switch forwarding STP BPDUs (most do), the 1910 notices a loop to ...
- 81.5k
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
7
votes
Accepted
Accessing devices on different subnets using a switch
Now I can commonly deduce that both the devices are part of the 192.168.0.0/16 network. Is that a correct assumption.
No, that's incorrect. You're using netmask 255.255.255.0, so that are two ...
- 17k
7
votes
Accepted
Is there a way to detect how many switches are between a host and the router?
No, there isn't. Switches are transparent devices. The frames which the host sends will be the same frames as the host (a router is just a host to a switch) on the other end of the switches receives. ...
- 98.3k
7
votes
Accepted
How IP helper address works?
Using the ip helper-address command sets up a DHCP relay. DHCP only works on the LAN to which it is connected because it uses broadcast, which cannot cross a router. To remedy that situation, DHCP ...
- 98.3k
7
votes
Can a switch that does NOT support VLAN capability be considered a managed switch if it has other features?
Yes, "manageable" obviously refers to the fact that you can manage the switch, rather than to one specific feature such as VLAN.
Among other things, some useful features such a switch could have:
...
- 19.4k
7
votes
Accepted
Does it make sense to map a VLAN to each LAN?
Using VLANs is like breaking a switch into multiple unconnected switches. On a single switch, no hosts on a VLAN will ever see any traffic for a different VLAN. Traffic must pass through a router, ...
- 98.3k
7
votes
LACPDU packets to pass through unmanaged switch
As Ron Trunk pointed out, LACP uses a special multicast OUI on its frames. Your unmanaged switch does not recognize the OUI, only that it is multicast, and it sends the multicast frames to every other ...
- 98.3k
Only top scored, non community-wiki answers of a minimum length are eligible