All Questions
155
questions
44
votes
15
answers
84k
views
How can I diagnose a bridging (ethernet) loop?
Given that spanning tree has failed (or you don't have any spanning tree) and get an ethernet loop, what's the best way to diagnose where the problem is?
Which switch?, which cable? and so on.
- 783
34
votes
1
answer
91k
views
Using SNMP to retrieve the ARP and mac-address tables from a switch
I would like to get ARP tables from a switch to a syslog-ng server that has been set up on Ubuntu Server 12.04 LTS. I have read about SNMP and I know the server will act as a manager and the switch as ...
- 695
30
votes
4
answers
75k
views
How does a switch learn a switch table?
Say the switch table is empty. If computer A sends a frame destined to computer B, the switch will broadcast asking who has the MAC address of B. What if C suddenly sends a frame to A? What is the ...
- 835
22
votes
4
answers
19k
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 ...
- 1,541
19
votes
2
answers
28k
views
Ethernet autonegotiation differences between (10M | 100M | 1G) Ethernet
I am studying for CCNA and on Wendell Odom's book is said that(regarding autonegotiation):
When autonegotiation fails on one node, to choose (half/full-duplex) we must use the rule:
If you have a 10/...
- 821
16
votes
3
answers
5k
views
Why would a switch be connected to a router using three ethernet cables?
In our rented office, we have a router (BT smart hub) connected to a large switch (model unknown). The two are connected using three ethernet cables, thus:
-----------------------
| 1 2 3 4 ...
- 273
16
votes
4
answers
6k
views
What happens when 2 computers transmits at the same time to a 3rd one in a full duplex switch?
Consider the following scenario:
I have 2 PC's (PC1 and PC2) that wants to transmit at the same time to PC3 in a full duplex ethernet switch. Let's consider that all ports are in the same VLAN, so ...
15
votes
3
answers
29k
views
How does a switch know where to route packet, when there is another switch in front of the destination?
I am just wondering how a switch does know how to route packets to destinations "hidden" behind another switch.
In my understanding a switch has a table that maps each of its hardware ports to exactly ...
- 253
14
votes
2
answers
25k
views
Does the source MAC address of a frame change when it passes through several switches? [duplicate]
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?
- 175
13
votes
2
answers
47k
views
What purpose is the Uplink port in layman's terms and do I need it?
I have an old Linksys switch (EZXS55W) and it has worked fine for many years now, but I tried to hook something up today to the last open port and noticed the device didn't work when I did this. When ...
- 233
13
votes
2
answers
4k
views
Switchport in half duplex - Download speed suffering but upload was fine
A user had issues with download speed from the Internet. The connection to the Internet is 100 Mbit/s. The user got around 7 Mbit/s downstream and around 80 Mbit/s upstream.
I tested from my computer ...
- 7,508
12
votes
5
answers
2k
views
Do faster segments of a network mean faster flow rate or lower latency?
This is another one of those hypothetical questions. I've been trying to figure out whether or not having a faster 'segment' of a network in between host A and host B will translate into a faster flow ...
- 515
10
votes
1
answer
8k
views
If two NICs are bonded and connected to different switches how does a router decide which switch to forward the packets to?
I am trying to understand how the architecture works in case of NIC Bonding. The scenario is: There are 2 NICs on the same system. Both are bonded to support failover and load balancing. Hence the IP ...
- 201
10
votes
2
answers
2k
views
Can a switch that does not support VLAN process traffic from a Trunk that is not the native VLAN
Recently encountered a setup where the engineer had a Multilayer Cisco switch with a trunk carrying VLAN 41 to an HP switch that did not support VLANs.
What should the HP switch do with the 802.1q ...
- 499
10
votes
4
answers
193k
views
What can cause "FastEthernet is up, line protocol is down" on a Cisco Switch?
I wonder what can cause the first line output of the command show interfaces to be: FastEthernet is up, line protocol is down.
In other words,
Is the cable that is connected to the local interface, ...
- 101