Hot answers tagged

17 votes
Accepted

Switchport mode access VLAN & switchport mode trunk on one interface

No this isn't doing anything. When the port is in trunk mode, then any "switchport access" statements are not used. The same is true with a port in access mode with any "switchport trunk" statements....
user avatar
  • 26.7k
15 votes
Accepted

Which VLANs are allowed on this trunk?

When you configure a trunk link with the command: (config-if)#switchport mode trunk all the vlans will be allowed in the trunk link. If you want to control which VLANs are allowed in a trunk link ...
user avatar
  • 1,064
9 votes

VLAN Tagging on Trunk Port

It will be sent out all ports on the native (untagged) VLAN. If there is no native VLAN, the packet is dropped.
user avatar
  • 62.5k
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 ...
user avatar
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 ...
user avatar
  • 70.5k
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 ...
user avatar
7 votes

VLAN links for IP Cameras

The short answer is, your proposed additional fiber in the diagram will not gain you any real advantage for VLAN 3. All traffic from Packaging or Fiberglass, destined to the server in Shipping on ...
user avatar
  • 8,258
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 ...
user avatar
  • 62.5k
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 ...
user avatar
  • 18.4k
7 votes
Accepted

The best way to understand Vlans?

Think of each VLAN as a single switch (or switch group). VLANs work by logically partitioning a single physical infrastructure. Each port is logically connected to one of the VLANs = one of the ...
user avatar
  • 70.5k
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 ...
user avatar
  • 70.5k
6 votes

Switchport mode access VLAN & switchport mode trunk on one interface

If you use the port as trunk you can safely remove the switchport access vlan 100 line. If you set the "mode trunk" in fact the port act as a trunk, the "switchport access vlan 100" still in the ...
user avatar
  • 226
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 ...
user avatar
  • 2,736
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 "...
user avatar
  • 26.7k
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 ...
user avatar
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. ...
user avatar
  • 62.5k
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, ...
user avatar
  • 18.4k
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 ...
user avatar
  • 4,481
5 votes

Native VLAN on Trunk port of Zyxel GS1910

Depending on the model - it may not support both tagged and untagged traffic on the same switchport. The GS1910 is one such model. Either tag all or tag none. Just got off the phone with Tech ...
user avatar
  • 51
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 ...
user avatar
  • 93.6k
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 ! ...
user avatar
  • 93.6k
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 ...
user avatar
  • 62.5k
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; ...
user avatar
  • 15.9k
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 ...
user avatar
  • 93.6k
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 ...
user avatar
  • 93.6k
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 ...
user avatar
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 ...
user avatar
  • 70.5k
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 ...
user avatar
  • 62.5k
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 ...
user avatar
  • 93.6k
5 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 an IP subnet. Just connect away. VLANs allow you to split (partition) a shared switched ...
user avatar
  • 70.5k

Only top scored, non community-wiki answers of a minimum length are eligible