Cisco Etherchannel Mode
When configuring Etherchannel, if I understand :
- if one switch has mode ON the other should be ON too to form a channel.
-if one switch has mode Desirable, the other switch should either be Auto or Desirable to form a channel
- if one switch has mode Active, the other is passive. will this form an Ether channel ?
***I have heard that it is best practice to stay away from mode ON. I am not sure why ?
Thanks
SW1(config-if-range)#chann
active Enable LACP unconditionally
auto Enable PAgP only if a PAgP device is detected
desirable Enable PAgP unconditionally
on Enable Etherchannel only
passive Enable LACP only if a LACP device is detected
- if one switch has mode ON the other should be ON too to form a channel.
-if one switch has mode Desirable, the other switch should either be Auto or Desirable to form a channel
- if one switch has mode Active, the other is passive. will this form an Ether channel ?
***I have heard that it is best practice to stay away from mode ON. I am not sure why ?
Thanks
SW1(config-if-range)#chann
active Enable LACP unconditionally
auto Enable PAgP only if a PAgP device is detected
desirable Enable PAgP unconditionally
on Enable Etherchannel only
passive Enable LACP only if a LACP device is detected
ASKER
The potential problem with on-on is that you are forcing the ports into a channel even if the ports are not correctly configuredExample ?
All the ports that make up the group are configured as a trunk but don't have the same VLANs allowed. Or one of them has a different native VLAN.
An easy way to overcome that problem would be to default the member ports before configuring etherchannel, and then apply configurations to the port channell.
eg
default int range gi1/1 - 4
etc
You can also use the default command on the port channell and then configure desired options eg trunk etc
Device configurations are based solely on preferences based on desired goal.
Flat generalizations to stay away from a configuration are usually based on the common configurations out there. 1 single configuration would not work for ALL situations.
Best thing is to know what your options are and what the advantanges and consequences are, and make an informed decision.
On-On gives you full control as it eliminates negotiation among other benefits. Connects faster, however, you must know what you're doing.
Negotiation guarantees consistency. You don't have to be a guru as it does most of the work for you.
As you can see below, the modes highlight the different proprietory or non-proprietory modes. PAGP (Cisco), LACP (Non-Proprietory)
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_13_ea1/configuration/guide/3550scg/swethchl.html#wp1028480
Table 29-1 EtherChannel Modes
Active
Places an interface into an active negotiating state, in which the interface starts negotiations with other interfaces by sending LACP packets. - Non-Proprietory
Auto
Places an interface into a passive negotiating state, in which the interface responds to PAgP packets it receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets. - Cisco
Desirable
Places an interface into an active negotiating state, in which the interface starts negotiations with other interfaces by sending PAgP packets. - Cisco
On
Forces the interface into an EtherChannel without PAgP or LACP. With the on mode, a usable EtherChannel exists only when an interface group in the on mode is connected to another interface group in the on mode. - No protocol
Passive
Places an interface into a passive negotiating state, in which the interface responds to LACP packets that it receives, but does not start LACP packet negotiation. This setting minimizes the transmission of LACP packets. - Non Proprietory.
You can also compare with Routing protocols.
Static - No negotiation
EIGRP Cisco Proprietory
OSPF Non Proprietory
eg
default int range gi1/1 - 4
etc
You can also use the default command on the port channell and then configure desired options eg trunk etc
Device configurations are based solely on preferences based on desired goal.
Flat generalizations to stay away from a configuration are usually based on the common configurations out there. 1 single configuration would not work for ALL situations.
Best thing is to know what your options are and what the advantanges and consequences are, and make an informed decision.
On-On gives you full control as it eliminates negotiation among other benefits. Connects faster, however, you must know what you're doing.
Negotiation guarantees consistency. You don't have to be a guru as it does most of the work for you.
As you can see below, the modes highlight the different proprietory or non-proprietory modes. PAGP (Cisco), LACP (Non-Proprietory)
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_13_ea1/configuration/guide/3550scg/swethchl.html#wp1028480
Table 29-1 EtherChannel Modes
Active
Places an interface into an active negotiating state, in which the interface starts negotiations with other interfaces by sending LACP packets. - Non-Proprietory
Auto
Places an interface into a passive negotiating state, in which the interface responds to PAgP packets it receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets. - Cisco
Desirable
Places an interface into an active negotiating state, in which the interface starts negotiations with other interfaces by sending PAgP packets. - Cisco
On
Forces the interface into an EtherChannel without PAgP or LACP. With the on mode, a usable EtherChannel exists only when an interface group in the on mode is connected to another interface group in the on mode. - No protocol
Passive
Places an interface into a passive negotiating state, in which the interface responds to LACP packets that it receives, but does not start LACP packet negotiation. This setting minimizes the transmission of LACP packets. - Non Proprietory.
You can also compare with Routing protocols.
Static - No negotiation
EIGRP Cisco Proprietory
OSPF Non Proprietory
ASKER
Negotiation guarantees consistency. You don't have to be a guru as it does most of the work for you.Did not know that
I'm not sure what was meant by that, but if the physical port configurations are not identical, PAgP or LACP will not correct that. It will simply errdisable the ports.
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ASKER
I conclude that LACP and PAgP are safer..?
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Thank you Guys!
Desirable-Desirable = etherchannel
Desirable-Auto = etherchannel
Auto-Auto = not etherchannel
Active-Active = etherchannel
Active-Passive = etherchannel
Passive-Passive = not etherchannel
The potential problem with on-on is that you are forcing the ports into a channel even if the ports are not correctly configured. And since spanning tree can't see the individual ports, a broadcast storm could result. With PAgP or LACP, the ports will go error disable if a problem arises.