philb19
asked on
trunking and spanning tree
Hi
when switch's are connected together - What are the advantages of trunking in terms of preventing L2 loops?.
If i uplink over access ports (without portfast on) - is this ok?
forgetting about VLAN tagging and carrying multiple vlan in this question (and presuming i have no stacking cables) -
Is there any other reason/s to trunk your uplinks between switches?
Does a trunk help in avoiding loops if so can someone explain please thanks
when switch's are connected together - What are the advantages of trunking in terms of preventing L2 loops?.
If i uplink over access ports (without portfast on) - is this ok?
forgetting about VLAN tagging and carrying multiple vlan in this question (and presuming i have no stacking cables) -
Is there any other reason/s to trunk your uplinks between switches?
Does a trunk help in avoiding loops if so can someone explain please thanks
Trunking doesn't help to prevent loops. The multilink trunk is considered one link by spanning tree. Using multiple links between switches that are not trunked will be detected as a loop.
Trunking allows you to have a bigger pipe between switches and the things you mentioned above.
Spanning tree works by sending packets out each port and listening to see if they are heard back on a different port which would imply there is a second link to the same switch in the topology.
Trunking allows you to have a bigger pipe between switches and the things you mentioned above.
Spanning tree works by sending packets out each port and listening to see if they are heard back on a different port which would imply there is a second link to the same switch in the topology.
You can have an mulilink (port channel), single vlan, uplink also and be seen as one link.
The only difference is one carries multiple vlans and the other doesn't.
There is no bandwidth advantages between an uplink and a trunk, so I don't understand the "bigger pipe" statement.
The only difference is one carries multiple vlans and the other doesn't.
There is no bandwidth advantages between an uplink and a trunk, so I don't understand the "bigger pipe" statement.
ASKER
thanks - yes I have also read of "bandwidth or bigger pipe" advantages of trunk - either I misunderstand or not true - I cant understand how? it could? - anyone please explain
If that can be explained it will be totally new to me.
Only think I can think of is that in HP lingo, they call port channels, trunks. This is not the trunking we are talking about though.
A gig port carrying a trunk that is tagging several vlans don't seem to have any bandwidth advantages than a gig port that is uplinking one vlan. If anything the uplink of the one vlan would have more bandwidth since its the only vlan using the link.
Only think I can think of is that in HP lingo, they call port channels, trunks. This is not the trunking we are talking about though.
A gig port carrying a trunk that is tagging several vlans don't seem to have any bandwidth advantages than a gig port that is uplinking one vlan. If anything the uplink of the one vlan would have more bandwidth since its the only vlan using the link.
Soulja is on track with is "HP terms" comment.
In the Cisco world a trunk is a connection between switches that carries multiple tagged VLAN's.
In the most of the rest world (not just HP) a trunk is multiple physical connections between two switches that appear as single logical connection. In Cisco terms this is a etherchannel, in more generic terms this is called link aggregation.
Now if you are using the term trunk to describe link aggregation, then yes it does prevent loops because instead of two independent connection between two switches (which is a loop) you have "one" logical connection (which is not a loop).
In the Cisco world a trunk is a connection between switches that carries multiple tagged VLAN's.
In the most of the rest world (not just HP) a trunk is multiple physical connections between two switches that appear as single logical connection. In Cisco terms this is a etherchannel, in more generic terms this is called link aggregation.
Now if you are using the term trunk to describe link aggregation, then yes it does prevent loops because instead of two independent connection between two switches (which is a loop) you have "one" logical connection (which is not a loop).
Yes, as Soujla says, trunk means link-bundling in HP-talk.
Cisco VLAN Trunk = HP Tagged Port
Cisco PortChannel = HP Trunk
HP do things the opposite way to Cisco in terms of configuring ports and VLANs.
In Cisco we do:
interface range GigabitEthernet0/1 - 4
switchport mode trunk
switchport trunk allowed vlan 10,20,30
...but in HP we do:
vlan 10
tagged 1-4
vlan 20
tagged 1-4
vlan 30
tagged 1-4
Back to the question around access ports between switches...
If you configure two switches with an access link between them, the traffic coming into the switch would be placed on whichever VLAN the port is configured to use (if it's a Cisco switch). So,
Switch1
interface GigabitEthernet0/1
switchport mode access
switchport access vlan 10
Switch2
interface GigabitEthernet0/1
switchport mode access
switchport access vlan 20
All traffic going from VLAN10 on switch1 would be placed into VLAN20 on switch2, and all traffic from switch2 on VLAN20 would go into VLAN10 on switch1.
Access ports between switches don't specifically 'have' to use the same VLAN ID.
Cisco VLAN Trunk = HP Tagged Port
Cisco PortChannel = HP Trunk
HP do things the opposite way to Cisco in terms of configuring ports and VLANs.
In Cisco we do:
interface range GigabitEthernet0/1 - 4
switchport mode trunk
switchport trunk allowed vlan 10,20,30
...but in HP we do:
vlan 10
tagged 1-4
vlan 20
tagged 1-4
vlan 30
tagged 1-4
Back to the question around access ports between switches...
If you configure two switches with an access link between them, the traffic coming into the switch would be placed on whichever VLAN the port is configured to use (if it's a Cisco switch). So,
Switch1
interface GigabitEthernet0/1
switchport mode access
switchport access vlan 10
Switch2
interface GigabitEthernet0/1
switchport mode access
switchport access vlan 20
All traffic going from VLAN10 on switch1 would be placed into VLAN20 on switch2, and all traffic from switch2 on VLAN20 would go into VLAN10 on switch1.
Access ports between switches don't specifically 'have' to use the same VLAN ID.
ASKER
hey thanks for bringing this up craigbeck - As I am a bit confused as to an article which states that 2 switches (diff vlan) connected together via access ports makes - " 1 Broadcast domain" - All i have read and understood is that a VLAN "is" a broadcast domain - please read below - and advise if they are right that the "2" seperate PCs in different vlans are in "1" broadcast domain
http://journey4ccie.com/2013/01/09/vlans-trunk-links-and-access-ports-here-is-the-trick/
http://journey4ccie.com/2013/01/09/vlans-trunk-links-and-access-ports-here-is-the-trick/
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ASKER
ok - what if in their diagram the link (both ports of switch connection were trunk ports) - im guessing the frame would then be tagged with the source vlan and "would not" be able to ping each other - as PCs on separate VLANs - same ip subnet does not matter ? - is that correct? thanks again
If the links were trunks that would create several broadcast domains - one per VLAN. Indeed, when a frame passes from one switch to another it would be tagged in the correct VLAN when it leaves the source switch to cross the trunk. When it gets to the other switch the frame will be placed on whichever VLAN was indicated in the 802.1q header.
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Only difference between the two is one tags multiple vlans and the other only carries one vlan.
If you uplink with an access port you would not enable portfast. Portfast is only for interfaces with end hosts (servers, computers, printers, etc.
So no advantages.