adimit
asked on
Cisco 3750 spanning tree portfast
Let’s say I am configuring my fast Ethernet ports on a 3750
Some ports have the following configuration (Lets call this config1):
interface FastEthernet1/1
switchport access vlan 100
spanning-tree portfast
Other ports have the following configuration (Lets call this config2)
interface FastEthernet1/6
switchport access vlan 100
The following are my spanning tree commands:
spanning-tree mode rapid-pvst
spanning-tree etherchannel guard misconfig
spanning-tree extend system-id
spanning-tree uplinkfast
spanning-tree backbonefast
Questions:
1. Does this mean that I can only plug Ethernet connections into config1?
2. What happens if I plug an Ethernet cable into a port with config2?
3. Can I just disable a port completely
4. What if I wanted to connect a switch into a fast Ethernet port instead of a fiber port? Would I have to make that port a trunk port? If so will all inter VLAN routing work.
The reason for the question is that I have read articles that have told me not to plug cables into particular ports that do not have spanning tree portfast for fear of flooding, broadcast storms etc..
Some ports have the following configuration (Lets call this config1):
interface FastEthernet1/1
switchport access vlan 100
spanning-tree portfast
Other ports have the following configuration (Lets call this config2)
interface FastEthernet1/6
switchport access vlan 100
The following are my spanning tree commands:
spanning-tree mode rapid-pvst
spanning-tree etherchannel guard misconfig
spanning-tree extend system-id
spanning-tree uplinkfast
spanning-tree backbonefast
Questions:
1. Does this mean that I can only plug Ethernet connections into config1?
2. What happens if I plug an Ethernet cable into a port with config2?
3. Can I just disable a port completely
4. What if I wanted to connect a switch into a fast Ethernet port instead of a fiber port? Would I have to make that port a trunk port? If so will all inter VLAN routing work.
The reason for the question is that I have read articles that have told me not to plug cables into particular ports that do not have spanning tree portfast for fear of flooding, broadcast storms etc..
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
ASKER
Hello
I beleive the following summarizes what I was told. Let me know if I am wrong:
1) If the port is not connected to any device –OR– its purpose in unknown –OR– the port is connected to another switch then “spanning-tree portfast” should NOT be set.
2) If the port is connected to a server or a non-switch device, then it is safe to enable “spanning-tree portfast”
I beleive the following summarizes what I was told. Let me know if I am wrong:
1) If the port is not connected to any device –OR– its purpose in unknown –OR– the port is connected to another switch then “spanning-tree portfast” should NOT be set.
2) If the port is connected to a server or a non-switch device, then it is safe to enable “spanning-tree portfast”
That's correct. Although if the port is not connected to any device then it really doesn't matter how the port is set. If I know that the purpose of the switch is primarily to support hosts/servers then I might turn it on on all user ports, connected or not.
There is a feature called "bpdu guard" which will shut down the port if it sees BPDUs entering a port that had portfast enabled. I think whether it's enabled by default depends on the model or version of software, but you can turn it on if it isn't already. That way you can turn on portfast everywhere (except uplinks) and if someone plugs in a little switch under their desk, the port will shut down until you turn off portfast.
There is a feature called "bpdu guard" which will shut down the port if it sees BPDUs entering a port that had portfast enabled. I think whether it's enabled by default depends on the model or version of software, but you can turn it on if it isn't already. That way you can turn on portfast everywhere (except uplinks) and if someone plugs in a little switch under their desk, the port will shut down until you turn off portfast.
ASKER