EC-5-CANNOT_BUNDLE2: vlan mask is different

[johnnylingo]

Cisco 3750-E stack running 15.0(2)SE8, attempting to bring up port channel to 2921 router.  First link comes up and bundles, but I get this on the second one:

Jan  5 13:04:34 PST: %EC-5-CANNOT_BUNDLE2: Gi2/0/51 is not compatible with Gi1/0/51 and will be suspended (vlan mask is different)

But the ports are configured exactly the same:

interface GigabitEthernet1/0/51
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 100,200,300
 switchport mode trunk
 logging event bundle-status
 channel-group 1 mode on
!
interface GigabitEthernet2/0/51
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 100,200,300
 switchport mode trunk
 logging event bundle-status
 channel-group 1 mode on

!

interface Port-channel1
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 100,200,300
 switchport mode trunk
 logging event trunk-status
 logging event bundle-status

!

Tried bringing the second port out of the bundle, setting vlan mask, and re-adding it.  No joy. 

[Cisco Freak]

Hi,

Can you please put Gi2/0/51 to default configuration and then try adding it part of the port-channel.

CF

[InayathUlla Sharieff]

From my side the action plan would be:-

1- Default the interfaces ( G1/0/51 & G2/0/51= cmd: default int G1/0/51 & 2/0/51)

2- Delete the port-channel ( conf t@ no int po1)

3- Shut down the physical interfaces( int g1/0/51,2/0/51- shut)

4- Create the Port-channel( 

interface Port-channel1
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 100,200,300  
 switchport mode trunk
 logging event trunk-status
 logging event bundle-status

5- Apply the port-channel config to the physical interfaces.

interface GigabitEthernet1/0/51 & interface GigabitEthernet2/0/51

channel-group 1 mode on

6- Unshut the physical interfaces.

int GigabitEthernet1/0/51 & interface GigabitEthernet2/0/51

no shut

Provide us the result. Make sure you only apply port-channel config on the physical interface as this will inherit the config from the PO.

HTH

Regards

Inayath

[johnnylingo]

I did a shut/no shut on Po1, everything then started working.  Go figure.  

[jerlewein]

So here's the deal. 
It seems to matter whether your PoX interface gets created before you place physical interfaces as channel-group X mode {whatevs}.

I just experimented with this on some shrouters of varying lineage. The take-away I have is this:
If you put interfaces into channel-groups before the PoX interface for that group exists,
it throws this generic message about an invalid VLAN mask and the channel-group will fail to come up.
From the opposite side of, say, an L2 LACP trunk to another switch, that switch will tell you that the remote side's LACP is not a match.

If you go back to your out-of-order-created interfaces and remove the channel-group statement (no channel-group X mode etc) and also destroy the PoX interface (no int PoX) then - start over and FIRST create your PoX interface, THEN place the physical interfaces in it using the channel-group X mode etc statement in the interface config - it WILL work.

just because you know how the end-config is going to work, it does seem to matter about the order in which config statements are entered, as this will affect the underlying interaction between the VLAN database, LACP settings, and virtual interfaces.

Anyway I had fun.

[ediwamoto]

Please try:
1. remove the switchport trunk allowed in this physical ports:
2. Port-channel 1 add vlan1 in the allowed vlans. 

interface GigabitEthernet1/0/51
 switchport trunk encapsulation dot1q
 switchport mode trunk
 logging event bundle-status
 channel-group 1 mode on
!
interface GigabitEthernet2/0/51
 switchport trunk encapsulation dot1q
 switchport mode trunk
 logging event bundle-status
 channel-group 1 mode on

!

interface Port-channel1
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 1,100,200,300
 switchport mode trunk
 logging event trunk-status
 logging event bundle-status

3. In last try, remove the switchport trunk allowed in the port-channel:
interface Port-channel1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 logging event trunk-status
 logging event bundle-status

[ANROD]

if helps somebody, I was having the same issue as described, and I restarted the Po interface... and then all sudden started working. My EtherChannel links were between a 6800 ( in different line cards) and 3850-XS STACK(ports going to different stack members.)