网络工程 - Etherchannel 尝试通过禁用的端口转发流量 - 吾爱随笔录

我正在对连接到由三个 3750G 交换机组成的堆栈的 WLC 的间歇性连接问题进行故障排除。开关的部件号和软件版本为：

Switch   Ports  Model              SW Version              SW Image
------   -----  -----              ----------              ----------
     1   12     WS-C3750G-12S      12.2(35)SE5             C3750-IPBASE-M
*    2   52     WS-C3750G-48TS     12.2(35)SE5             C3750-IPBASE-M
     3   52     WS-C3750G-48TS     12.2(35)SE5             C3750-IPBASE-M

WLC 启用了 LAG，因此在堆栈中配置了 Po4，包括 4 个端口以连接 WLC 的 4 个物理端口：

SW#show etherchannel 4 summary
Flags:  D - down        P - in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 4
Number of aggregators:           4

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
4      Po4(SU)          -        Gi2/0/51(P) Gi2/0/52(P) Gi3/0/51(P)
                                 Gi3/0/52(P)

SW#

物理和端口通道接口的配置是：

interface GigabitEthernet2/0/51
 switchport trunk encapsulation dot1q
 switchport mode trunk
 mls qos trust cos
 channel-group 4 mode on
end
!
interface GigabitEthernet2/0/52
 switchport trunk encapsulation dot1q
 switchport mode trunk
 mls qos trust cos
 channel-group 4 mode on
end
!
interface GigabitEthernet3/0/51
 switchport trunk encapsulation dot1q
 switchport mode trunk
 mls qos trust cos
 channel-group 4 mode on
end
!
interface GigabitEthernet3/0/52
 switchport trunk encapsulation dot1q
 switchport mode trunk
 mls qos trust cos
 channel-group 4 mode on
end
!
interface Port-channel4
 switchport trunk encapsulation dot1q
 switchport mode trunk
end

以太网通道负载平衡是基于源和目标 IP 地址完成的：

SW#show etherchannel load-balance
EtherChannel Load-Balancing Configuration:
        src-dst-ip

EtherChannel Load-Balancing Addresses Used Per-Protocol:
Non-IP: Source XOR Destination MAC address
  IPv4: Source XOR Destination IP address
  IPv6: Source XOR Destination IP address

SW#

在故障排除期间，我尝试禁用以太网通道的 4 个端口中的 2 个，发现有时交换机试图通过禁用的端口转发流量：

SW#show etherchannel 4 summary
Flags:  D - down        P - in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port

Number of channel-groups in use: 4
Number of aggregators:           4

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
4      Po4(SU)          -        Gi2/0/51(D) Gi2/0/52(D) Gi3/0/51(P) 
                                 Gi3/0/52(P)
SW#
SW#
SW#
SW#test etherchannel load-balance interface Po4 ip 10.0.1.254 10.0.1.251
Would select Gi2/0/52 of Po4  
SW#

我理解以太通道负载平衡永远不应该尝试通过关闭或禁用的端口转发流量，即使端口被配置为以太通道的一部分。

你们中有人知道这种行为的任何充分理由吗？