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New Member

Issue with multiple 3750G-24T

I have about 10 different 3750G stack where I cannot make a larger than 3 GB ether channel trunk uplink to my 6 stack 3750g distribution stack.

It keep saying suspended due to being 100M and not compatible with others being 1000M.

Is there a limitation on etherchannels on these switches as its happening on multiple switches? I have them stacked in 2 using ports g1/0/23 - 24 and g2/0/23 - 24, cannot get 3rd port upand running.

6 REPLIES
New Member

Re: Issue with multiple 3750G-24T

Hi, cisco still has restriction when it come to configuring etherchannel, there are restrictions on the number of ports allowed in a bundle, requirement of adjacent ports and more. Have a look at a great document on etherchanne requirements and setup below. I hope this is helpful

Catalyst 3750 Series Switches

Refer to the support page for the Catalyst 3750 Series Switches for more information on these switches.

Catalyst 3750 series switches support both Layer 2 and Layer 3 EtherChannel, with up to eight compatibly configured Ethernet interfaces. All interfaces in each EtherChannel must be the same speed. All interfaces in each EtherChannel must have a configuration as either Layer 2 or Layer 3 interfaces.

The EtherChannel can be formed with interfaces on any switch and across switches within a single switch stack. Refer to Cross-Stack EtherChannel on a Catalyst 3750 Switch Configuration Example for more information on Cross-Stack EtherChannel.

The Catalyst 3750 series switches support a maximum of 12 EtherChannels with configuration on a stack.

In order to balance the traffic load across the links in a channel, EtherChannel load balancing can use any of these addresses:

MAC addresses or IP addresses

source or destination addresses

both source and destination addresses

The default configuration is the forward of source MAC addresses. Refer to Configuring EtherChannel for more information on load balancing on the 3750.

Catalyst 3750 series switches support EtherChannels in Cisco IOS Software Release 12.1(11)AX or later.

http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a0080094646.shtml#topic6a

New Member

Re: Issue with multiple 3750G-24T

I dont understand. It says the 3750G supports 48 etherchannels per stack, not 12?

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_data_sheet0900aecd80371991.html

Here it says:

Up to 48 EtherChannel groups are supported per stack.

New Member

Re: Issue with multiple 3750G-24T

Hi what do you see when you enter?

switch# show etherchannel xxx summary

New Member

Re: Issue with multiple 3750G-24T

Hi, if you are configuring the link manually all parimeters have to be set the same on both links. Since I think you have all cisco switches check your PAgP and see if the port will form there own etherchannel link.

(config)# int g3/0/23

(config-if)#channel-group 1 mode desirable

(config-if)#no switchport

(config-if)#int g3/0/24

(config-if)#no switchport

(config-if)#channel-group 1 mode desirable

(config-if)#int port-channel 1

(config-if)#switchport mode trunk

Purple

Re: Issue with multiple 3750G-24T

Sounds like you have 1 or more ports that are not exactly the same as the others. All ports must be configured exactly the same for all parameters such as speed and duplex . For cross stack you must either force the channel on or you can use LACP , PAGP is not an option on cross stack.

New Member

Re: Issue with multiple 3750G-24T

yes it seems like some bug or hardware limitation. All ports have same settings except for channel-group ## mode on.

If I move the 4th connection to another set of ports(asic), I dont have a problem.

very weird.

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