Link Aggregation Cannot Be Implemented Between an S5700 and a Non-Huawei Device

Publication Date:  2015-10-13 Views:  3636 Downloads:  0
Issue Description
As shown in Figure 2-1, links between the S5700 and Catalyst 3560 switches are bundled on the two switches, but the link aggregation function does not take effect.

Figure 2-1 Link aggregation between S5700 and Catalyst 3560 switches



Link aggregation configuration on the S5700:

#
interface Eth-Trunk22
port link-type trunk
port trunk allow-pass vlan 2 to 4094
mode lacp   //The link aggregation protocol is LACP.
#
interface GigabitEthernet0/0/1
eth-trunk 22
#
interface GigabitEthernet0/0/2
eth-trunk 22
#
interface GigabitEthernet0/0/3
eth-trunk 22
#
interface GigabitEthernet0/0/4
eth-trunk 22
#

Link aggregation configuration on the Catalyst 3560:

!
interface FastEthernet0/1
channel-protocol pagp   //The link aggregation protocol is PAgP.
channel-group 22 mode desirable
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/2
channel-protocol pagp
channel-group 22 mode desirable
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/3
channel-protocol pagp
channel-group 22 mode desirable
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/4
channel-protocol pagp
channel-group 22 mode desirable
switchport trunk encapsulation dot1q
switchport mode trunk
!
Handling Process
According to the configuration on the two switches, the link aggregation failure is caused by incorrect configuration on the Cisco switch, rather than the S5700.

The customer needs to contact Cisco for the solution to this problem.

After the PAgP protocol is replaced by LACP on the Catalyst 3560, link aggregation can be implemented between the two switches.

The LACP-based link aggregation configuration on the Catalyst3560 is as follows:

!
interface FastEthernet0/1
channel-protocol lacp   /The link aggregation protocol is LACP.
channel-group 22 mode active   //The working mode is active.
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/2
channel-protocol lacp    
channel-group 22 mode active    
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/3
channel-protocol lacp
channel-group 22 mode active
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface FastEthernet0/4
channel-protocol lacp
channel-group 22 mode active
switchport trunk encapsulation dot1q
switchport mode trunk
!
Root Cause
The S5700 uses the standard LACP protocol to implement link aggregation and its configuration is correct.

The Cisco Catalyst 3560 switch supports both LACP and Cisco proprietary PAgP protocol. Actually, the Catalyst 3560 uses PAgP but not LACP on the network. As a result, link aggregation cannot be implemented between the two switches.
Suggestions
When a Huawei switch needs to be connected to a non-Huawei device through bundled links, check whether the peer device uses the standard link aggregation protocol.

END