9
votes
Accepted
Portfast on Trunk port
Having portfast on a inter-switch link is not the best of ideas, indeed.
Switches and Bridges should take the time needed (going through listening/learning phases) to converge to a loop free L2 ...
- 8,826
8
votes
Accepted
The best way to understand Vlans?
A broadcast domain / L2 segment / VLAN has several weaknesses and is prone to a number of attack vectors, most importantly:
any host can directly talk to any other host
broadcasts from any host reach ...
- 82.7k
8
votes
Accepted
What is VLAN Hopping
VLAN hopping is when a client (unauthorized node) can add VLAN tags to its frames to enter VLANs that it's not supposed to be in or when it can generate MVRP/GVRP frames to make its port a member of ...
- 82.7k
8
votes
Accepted
spanning-tree port type edge trunk on port-channel vs physical interface
Strongly suggested: Configure both port-channel and its members identically (except of course for description and the channel-group and vpc bits).
As long as an interface is not configured to be ...
- 8,826
7
votes
Aren't Switch Access ports tagged?
I think you're confusing what goes on internally on the switch. How it keeps track of which ports are in which VLAN is up to the manufacturer.
It's important to remember that 802.1q frames are a ...
- 67.1k
7
votes
Accepted
What is difference between standard VLAN extended VLAN?
VLAN are introduced by the IEEE 802.1Q standard, which doesn't have this notion of standard or extended VLAN, nor made any difference between VLAN under or above 1005.
This is Cisco implementation ...
- 19.5k
7
votes
Do VLANs within a subnet need to have their own subnet for router on a stick?
I'm not understanding your exact problem because you don't provide enough detail but maybe this helps:
With rare exceptions, an IP subnet is mapped to a VLAN = broadcast domain = layer-2 network on a ...
- 82.7k
7
votes
Can a single subnet work across several switches?
Without VLANs, connected switches form a single broadcast domain - that is exactly what you need for a single IP subnet. Just connect away.
VLANs require managed switches and allow you to split (...
- 82.7k
7
votes
Accepted
Can a single subnet work across several switches?
Yes. You don’t even need a trunk. If all ports on both switches are access ports on Vlan 3, then the port connecting the two switches are on Vlan 3 and both switches form one broadcast domain on that ...
- 2,183
6
votes
Accepted
Building too large for ethernet runs
Fiber is not so expensive unless you are getting fleeced. Indeed, it can be cheaper than copper cabling. It's also the right solution to long runs.
Given the installation costs, it's likewise foolish ...
- 2,746
6
votes
Accepted
Port channel to two different switches
I understand that this is an incorrect configuration, but what was blocking traffic to the new switch? Is this part of the port channel or spanning tree or something else?
Nothing was actually "...
- 27.2k
6
votes
Assigning a single switchport to different VLANs
First of all an access port is by definition can only carry one Vlan.
Voice vlan is used, when if its actually a voice vlan traffic needed to be carried.
so lets say both vlans 232 and 233 are Data ...
- 61
6
votes
Do VLANs within a subnet need to have their own subnet for router on a stick?
Just to amplify on Zac’s answer: you have one subnet per vlan and vice versa. At the CCNA level, you can ignore the rare exceptions. The router on a stick has an (sub)interface in each subnet. ...
- 67.1k
6
votes
Accepted
cisco switchport trunk native vlan
The problem is not the traffic from the server to the switch, but the return traffic, from the switch to the server.
Since the VLAN is native, the switch will sent the traffic for this VLAN untagged, ...
- 19.5k
6
votes
Accepted
difference between switchport trunk encapsulation dot1q and switchport mode trunk
The switchport trunk encapsulation dot1q command tells the switch that the interface should use IEEE 802.1Q encapsulation on the frames when the interface is configured as a trunk. Basically 802.1Q ...
- 98.8k
6
votes
Accepted
Can't add VLAN in the "allowed VLAN"
You have to already have a VLAN in the allowed list (not "all") before you can use the add command to append to the existing list.
So, first, use: switchport trunk allowed vlan 52
Then you ...
- 4,690
5
votes
Accepted
How do I remove a vlan from a trunked port
In Cisco devices you can do the command with no in front of it: no switchport access vlan 12.
Putting the access VLAN on a trunk port does nothing unless the trunk goes down and the port reverts to ...
- 98.8k
5
votes
Accepted
How to encapsulate all VLAN traffic inside VXLAN
I think you are confusing a couple of concepts. Looking at the last configuration section of the document you have linked:
7.2) VXLAN without CVX
Configuration on VTEPs:
!
vlan 100
vlan 200
!
...
- 98.8k
5
votes
Best practice for connecting router to switch? (re: VLANs and multiple ports)
At the risk of expressing an opinion here, there is no such thing as "best practice." There are good practices, there are bad practices, and there are a lot in between. There is no best practice ...
- 67.1k
5
votes
VLAN Tags Being Different for a VoIP Phone vs. the Host Daisy-Chained to it?
Certainly this is the usual situation for the Cisco and Avaya phones I'm familiar with, as it's usual to keep voice and data traffic separate.
This is from a Cisco SPA504G phone web configuration; ...
- 16.2k
5
votes
VLAN Tags Being Different for a VoIP Phone vs. the Host Daisy-Chained to it?
A VoIP phone that chains to another device is a switch, and it negotiates a trunk between the phone and the switch. This happens with CDP or LLDP.
For example, a Cisco switch interface configured as ...
- 98.8k
5
votes
Native VLAN question
The native vlan just means the vlan is untagged on the trunk port. The vlan can be untagged on one trunk but tagged on another. In other words, “native” is in reference to a particular trunk port. ...
- 67.1k
5
votes
The best way to understand Vlans?
Before VLANs, we used to do it like this:
Use separate sets of switches for each area (servers, desktops, whatever)
Keep those LANs completely distinct (different IP address ranges and no wires in ...
- 16.2k
5
votes
increasing bandwidth between two Cisco switches?
The bandwidth on an interface is the bandwidth on the interface. It is possible to use multiple interfaces (up to eight) in a port channel between the switches to give you a greater aggregate ...
- 98.8k
5
votes
Accepted
How can I set the switchport's trunk protocol?
Only Cisco switch platforms that still support isl trunking need to have the trunking protocol configured.
Newer platforms have no support for isl trunking anymore, so the interface command ...
- 8,826
5
votes
Accepted
Use of VLAN allowed feature and security risk associated with not configuring it
Generally, you'll want to secure VLAN membership for all ports that you don't control on both link ends. If a trunk port - or rather the link partner - can simply join any VLAN they want then an ...
- 82.7k
5
votes
Partitioning between VLAN in a Trunk switch architecture
Most of the time, a computer is connected to an access port--not because of security, but because most computers don't need to switch VLANs. And since they don't switch, most NIC cards can't create ...
- 67.1k
5
votes
Why STP has to be disable on Trunk Ports?
You should not disable spanning tree on trunk interfaces. In fact, STP needs to be on links between the switches, which should be the trunk interfaces.
You can also leave STP enabled on the access ...
- 98.8k
5
votes
Accepted
Access and Trunk Port
What you have is correct. Changing the modes does not remove all of the configuration that the port previously had, in case you need to switch back for any reason. So, whatever it says in the ...
- 4,690
4
votes
VLAN, Trunk and OSPF
you really should start reading a bit more about what you're doing. A VLAN is a broadcast domain, so computers on separate VLANs are unable to communicate without the intervention of a routing device. ...
- 205
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