所以这里有一个奇怪的设置。在我工作的地方，我们有两个 Nexus 9k 交换机运行我们的核心网络 - 分别命名为 A 和 B，它们有 span 端口，可将流量发送到 Catalyst 2960-X，后者又将流量中继到另一个系统进行流量监控（不幸的是，该系统只有一个 NIC）
最初，我们在 VLAN 1000 的 Catalyst 交换机中使用中间 VLAN，尝试以能够被正确检测并传递给流量监控系统的方式交接流量，这样端口 46、46 和 47 都具有：
switchport mode access
switchport access vlan 1000
... 一切正常。但是，在移至新数据中心后，如果保持端口连接不变，一切就不再正常了。
我们还尝试将其作为 Catalyst 本地 SPAN 端口执行此操作，如下图所示，在取消配置交换机端口访问模式以转到直接 SPAN 行为后：
VLAN/接入端口方法和 SPAN 方法似乎都无法将流量传送到监控系统。Catalyst 上的接口统计数据show int gig 1/0/45显示show int gig 1/0/46流量增加，并且接收的数据包数量随着数据包计数器不断增加。但是，这不再通过 Cataylst 中的 SPAN 将流量中继到端口 48 - 其计数器显示零数据包活动，并且下游流量监控系统看不到通过该端口的流量。
有人知道我们如何才能让它再次工作吗？流量监控系统是一个专用设备，只有一个上行链路端口，因此我们无法将额外的 NIC 放入方程式中，通过单独的 NIC 将流量从每个交换机直接泵送到流量监视器，很遗憾……
Catalyst 跨度配置：
monitor session 1 source int gig 1/0/45 both
monitor session 1 source int gig 1/0/46 both
monitor session 1 dest int gig 1/0/48
Nexus 本地跨度配置（两者相同，请注意这不是 RSPAN 设置）：
monitor session 1
source vlan 20-21,121,150,160,270,300,400,500 both
destination interface Ethernet1/15
no shut
请注意，我们可以根据 Catalyst 端口 45 和 46 上的“接收”速率确认流量是来自 NEXUS 并到达 Catalyst 上的端口 45 和 46，它只是没有将流量从这两个端口传递到 Catalyst 上的端口 48。
另请注意，VLAN 1000 在网络上的其他地方不存在，并且此时不是正在运行；access删除了交换机端口配置，尝试使用标准 SPAN，但这两种机制都不起作用。（VLAN 1000 被用作直接的交换机内部专用 VLAN，以尝试欺骗系统将来自 Nexuses 的未标记数据包传递到监控系统所在的端口）
show monitor session 1 detail在 Catalyst 上请求的输出：
#show monitor session 1 detail
Session 1
---------
Type : Local Session
Description : -
Source Ports :
RX Only : None
TX Only : None
Both : Gi1/0/45-46
Source VLANs :
RX Only : None
TX Only : None
Both : None
Source RSPAN VLAN : None
Destination Ports : Gi1/0/48
Encapsulation : Native
Ingress : Disabled
Filter VLANs : None
Dest RSPAN VLAN : None
Catalyst 2960-X 当前运行的配置show run（部分已清理以隐藏敏感信息）：
Current configuration : 8036 bytes
!
! Last configuration change at 17:13:19 UTC Thu Apr 4 2019 by admin
! NVRAM config last updated at 16:20:59 UTC Mon Apr 1 2019 by admin
!
version 15.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
!
hostname catalyst
!
boot-start-marker
boot-end-marker
!
!
[username data snipped]
aaa new-model
!
!
aaa authentication login default local
aaa authentication enable default none
aaa authorization commands 15 default local
!
!
!
!
!
!
aaa session-id common
switch 1 provision ws-c2960x-48fps-l
!
!
!
!
!
!
!
!
!
crypto pki trustpoint TP-self-signed-2307906176
enrollment selfsigned
subject-name cn=IOS-Self-Signed-Certificate-2307906176
revocation-check none
rsakeypair TP-self-signed-2307906176
!
!
crypto pki certificate chain TP-self-signed-2307906176
certificate self-signed 01
[SNIP]
quit
spanning-tree mode pvst
spanning-tree extend system-id
!
!
!
!
vlan internal allocation policy ascending
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0
no ip address
!
interface GigabitEthernet1/0/1
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/2
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/3
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/4
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/5
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/6
description exagrid mgmt
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/7
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/8
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/9
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/10
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/11
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/12
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/13
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/14
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/15
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/16
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/17
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/18
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/19
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/20
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/21
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/22
description WAN Switch
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/23
description Core 9K A
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/24
description Core 9K B
switchport access vlan 255
switchport mode access
!
interface GigabitEthernet1/0/25
description UPLINK TO MGT NETWORK
switchport trunk allowed vlan 255
switchport mode trunk
!
interface GigabitEthernet1/0/26
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/27
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/28
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/29
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/30
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/31
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/32
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/33
description esx500 console
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/34
description esx501 Console
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/35
description esx502 Console
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/36
description esx503 Console
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/37
description esx504 Console
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/38
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/39
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/40
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/41
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/42
switchport access vlan 255
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet1/0/43
!
interface GigabitEthernet1/0/44
!
interface GigabitEthernet1/0/45
description Core A Monitor Port
!
interface GigabitEthernet1/0/46
description Core B Monitor Port
!
interface GigabitEthernet1/0/47
!
interface GigabitEthernet1/0/48
description Monitor Ports to Monitoring System
!
interface GigabitEthernet1/0/49
!
interface GigabitEthernet1/0/50
!
interface GigabitEthernet1/0/51
!
interface GigabitEthernet1/0/52
!
interface Vlan1
no ip address
!
interface Vlan255
ip address 10.1.255.21 255.255.255.0
!
interface Vlan1000
description SPAN collection
no ip address
!
ip http server
ip http secure-server
!
!
!
!
!
!
!
line con 0
line vty 0 4
timeout login response 300
transport input telnet ssh
line vty 5 15
timeout login response 300
transport input telnet ssh
!
!
monitor session 1 source interface Gi1/0/45 - 46
monitor session 1 destination interface Gi1/0/48
end
答案1
根据评论，似乎您没有在交换机上的 VLAN 数据库中创建 VLAN。
不使用全局命令为独立交换机创建 VLANvlan是常见的问题来源。使用中继的交换机通常启用了 VTP，并且 VLAN 数据库将由 VTP 填充。对于独立交换机和处于 VTP 透明模式的交换机，您需要确保创建交换机上使用的 VLAN。
这似乎解决了你的问题。