bad vlan mask...

what the hell does that mean... i'll tell you...

the hardware ports have to match the portchannel interface and vice versa, and of course you know this... but how do you detect it... a number of ways...

first off if you're going to make portchannels anyway, save the painful  configuration for the portchannel, don't waste typing on the physical interfaces, they will inherit from the portchannel...

here's an example:


DLS1(config)#int rang f0/3 - 4
DLS1(config-if-range)#sw mode trunk
DLS1(config-if-range)#sw trunk encap dot1q
DLS1(config-if-range)#channel-g 10 mode on
Creating a port-channel interface Port-channel 10

DLS1(config-if-range)#int po10
DLS1(config-if)#sw trunk native vlan 900
DLS1(config-if)#sw trunk allowed vlan 10,20,30,50,70,100

DLS1#sh run int f0/3
Building configuration...

Current configuration : 233 bytes
!
interface FastEthernet0/3
 description Channel to DLS2
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 900
 switchport trunk allowed vlan 10,20,30,50,70,100
 switchport mode trunk
 channel-group 10 mode on

this is basic stuff... and by the book...

DLS1#sh etherch summ

Number of channel-groups in use: 2
Number of aggregators:           2

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)          -        Fa0/1(P)    Fa0/2(P)   
10     Po10(SU)         -        Fa0/3(P)    Fa0/4(P)   

and likewise the portchannel will get the earlier garbage from f0/3 - 4...

DLS1#sh run int po10
Building configuration...

Current configuration : 177 bytes
!
interface Port-channel10
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 900
 switchport trunk allowed vlan 10,20,30,50,70,100
 switchport mode trunk

allowed vlan statements can get long, and it's easy to screw up a portchannel, especially if you make changes to the interfaces (f0/3 - 4 in this case)

the portchannel won't inherit from the interfaces...

DLS1(config)#int rang f0/3 - 4
DLS1(config-if-range)#sw trunk allowed vlan 10,20,30,50,100
DLS1(config-if-range)#
Jan  9 15:59:25.974: %EC-5-CANNOT_BUNDLE2: Fa0/3 is not compatible with Fa0/4 and will be suspended (vlan mask is different)
Jan  9 15:59:26.007: %EC-5-CANNOT_BUNDLE2: Fa0/3 is not compatible with Po10 and will be suspended (vlan mask is different)
Jan  9 15:59:26.007: %EC-5-CANNOT_BUNDLE2: Fa0/3 is not compatible with Po10 and will be suspended (vlan mask is different)
Jan  9 15:59:26.007: %EC-5-CANNOT_BUNDLE2: Fa0/4 is not compatible with Po10 and will be suspended (vlan mask is different)

that's the culprit... now suppose you weren't there to see the errors...

DLS1#sh etherchann summ

Number of channel-groups in use: 2
Number of aggregators:           2

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)          -        Fa0/1(P)    Fa0/2(P)   
10     Po10(SD)         -        Fa0/3(s)    Fa0/4(s)

you know you have a problem with the etherchannel, but you're not sure why... you could eye a comparison between sh run's on the interfaces and the portchannel, but that's kind of clumsy...

this will give you an instant answer...

DLS1#debug etherch all
PAgP/LACP Shim All debugging is on
DLS1#
Jan  9 16:06:58.338: FEC: pagp_switch_agc_compatable: comparing GC values of Fa0/3 Po10 flag = 1 1
Jan  9 16:06:58.338: FEC: pagp_switch_port_attrib_diff: Fa0/3 Po10 same
Jan  9 16:06:58.338: FEC: pagp_switch_agc_compatable: EC - attrib incompatable for Fa0/3; vlan mask is different
Jan  9 16:06:58.338: FEC: pagp_switch_choose_unique: Fa0/3 incompatable with agport Po10
Jan  9 16:06:58.338: FEC: pagp_switch_agc_compatable: comparing GC values of Fa0/4 Po10 flag = 1 1
Jan  9 16:06:58.338: FEC: pagp_switch_port_attrib_diff: Fa0/4 Po10 same
Jan  9 16:06:58.338: FEC: pagp_switch_agc_compatable: EC - attrib incompatable for Fa0/4; vlan mask is different
Jan  9 16:06:58.338: FEC: pagp_switch_choose_unique: Fa0/4 incompatable with agport Po10

yeah, it's telling you the damn allowed vlan's are different...

knowing that the interfaces inherit from the portchannel, just adjust the portchannel...

DLS1(config-if)#sw trunk allowed vlan 10,20,30,50,70,100
DLS1(config-if)#
Jan  9 16:13:28.014: %EC-5-CANNOT_BUNDLE2: Fa0/4 is not compatible with Po10 and will be suspended (vlan mask is different)
Jan  9 16:13:28.047: %EC-5-CANNOT_BUNDLE2: Fa0/4 is not compatible with Po10 and will be suspended (vlan mask is different)
Jan  9 16:13:28.878: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan50, changed state to up
Jan  9 16:13:28.878: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan70, changed state to up
Jan  9 16:13:29.037: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/3, changed state to up
Jan  9 16:13:29.087: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/4, changed state to up
Jan  9 16:13:30.027: %LINK-3-UPDOWN: Interface Port-channel10, changed state to up
Jan  9 16:13:31.034: %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel10, changed state to up

it's very nice how that works out...

DLS1#sh etherch summ

Number of channel-groups in use: 2
Number of aggregators:           2

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)          -        Fa0/1(P)    Fa0/2(P)   
10     Po10(SU)         -        Fa0/3(P)    Fa0/4(P)   

if you were in the data room you might have noticed the amber lights on the interfaces signifying suspended versus up (green), or down(darkness)...

oh yeah, if you're really serious about this shit, you're gonna need some switches...