Losing Connection with Etherchannel

[TOM FRANCHINA]

We have a new building where we added 3 network closets with 3750x stacks.We have 2 fiber gig ports connected to 2 microwave units and etherchanneled the to ports

We have the same setup at the corporate office except the connection is 2 fiber gig ports on a 6509. The 6509 is doing the routing

Now the problem is that we lost the connection to the management interface on only one of the three closets after a few days running. But some workstations at the corp office could reach it... others could not. The workstation were on the same VLAN. We solved the problem for a few days by shutting on of the fiber ports on the etherchannel. But is started happening again... now with PCs being installed at the new location.

The PC that was not working on the 3750x side could ping across to the 6509 but no further then that. It seems like an arp issue not routing because some devices are reachable and fully operational throughout the network.

Here is the configuration:

3750x:Cisco IOS Software, Version 12.2(55)SE1

Current configuration : 118 bytes
!
interface Port-channel1
switchport trunk encapsulation dot1q
switchport mode trunk
no snmp trap link-status
end

!
interface GigabitEthernet1/1/1
description 2gig to STB-6509
switchport trunk encapsulation dot1q
switchport mode trunk
spanning-tree link-type point-to-point
channel-group 1 mode desirable
end

!
interface GigabitEthernet1/1/2
description 2gig to STB-6509
switchport trunk encapsulation dot1q
switchport mode trunk
spanning-tree link-type point-to-point
channel-group 1 mode desirable
end

6509:IOS Version 12.2(18)SXF9

interface Port-channel7
description Vestal MicroWave
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
no snmp trap link-status
end

!
interface GigabitEthernet2/19
description Vestal IDU 1 Microwave
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
no snmp trap link-status
channel-group 7 mode desirable
end

!

interface GigabitEthernet2/20
description Vestal IDU 2 Microwave
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
no ip address
no snmp trap link-status
channel-group 7 mode desirable
end

Thanks Tom

[Leo Laohoo]

I would like to see the "sh logs" and the events when the etherchannel would flap.

[TOM FRANCHINA]

Leolaohoo,

The Etherchannel does not go down or flap. Here is the real problem:

Summary:

Site 1 has the 6509 and Site 2 has the 3750X.  Both sites are connected via two separate TrangoLink Microwaves.

Device A - Located at Site 1 - 10.10.1.1

Device B - Located at Site 1 - 10.10.1.2

Device C - Located at Site 2 - 10.29.1.1

Device D - Located at Site 2 - 10.29.1.2

Device A can ping device C

Device A can't ping device D

Device B can ping device C & D

If we shut down one of the two EtherChanneled ports, then A and B can both ping C & D

If we turn both EtherChanneled ports back on again, the problem immediately comes back.

It seems like it is random which source and destinations work and which ones do not.  It kind of seems like it might be related to the source MAC or something along those lines - where certain PC's can talk to certain devices, but other devices can't.

[handoko wiyanto]

hi tom,

any updates on the debug result?

regards,

[TOM FRANCHINA]

All,

We forced the Etherchannel Protocol to LACP on all links on both sides of the microwave and now all devices are pinging. Here is the config we used. Can anyone explain why this may have fixed the problem. Would LACP be better suited to work on a microwave then PAgP???

interface GigabitEthernet2/20

description Vestal IDU 2 Microwave

switchport

switchport trunk encapsulation dot1q

switchport mode trunk

no ip address

no snmp trap link-status

channel-protocol lacp

channel-group 8 mode active

end

!

interface GigabitEthernet2/19

description Vestal IDU 1 Microwave

switchport

switchport trunk encapsulation dot1q

switchport mode trunk

no ip address

no snmp trap link-status

channel-protocol lacp

channel-group 8 mode active

end

!

interface Port-channel8

description Vestal MicroWave

switchport

switchport trunk encapsulation dot1q

switchport mode trunk

no ip address

no snmp trap link-status

end

[handoko wiyanto]

hi Tom,

good to know that the link working fine with lacp.

i dont believe that pagp dont work well on microwave.

anyway, do you want to continue the troubleshooting on pagp, or you will use lacp instead?

regards,