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本文档介绍如何对Catalyst 3650/3850交换机上的PoE(以太网供电)Imax错误进行故障排除。Catalyst 3650/3850交换机使用PoE,以便通过连接到交换机的以太网电缆为外部设备(如无线接入点(AP)、IP电话等)供电。
当交换机上支持PoE的端口的功耗超过协商的功耗时,会出现Imax错误。当IEEE供电设备(PD)启动时,它被分类为类。根据设备所处的类别,作为电源设备(PSE)的交换机会为设备分配一定的瓦特。 稍后,使用思科发现协议(CDP)或链路层发现协议(LLDP)请求或多或少电源的设备可以重新协商。这是为了实现权力预算。
PD确保它不会消耗比分配的功率更多的功率。交换机通过设置Icutoff值来控制此操作。这是在控制器上设置为高标记的值。当设备超过Icutoff值时,交换机停止供电并记录Imax错误,该错误表示连接的设备超过协商瓦数。
Catalyst 3650/3850采用更强大的PoE控制器。如果Catalyst 3750等较旧设备在设置Icutoff值方面不支持较细粒度,则Catalyst 3650和3850会支持。这通常会导致人们认为Catalyst 3650/3850遇到旧设备所没有的问题。然而,在几乎所有情况下,这只是一种看法。较旧的设备对电源的管制粒度较小,允许PD比协商的设备消耗更多电源。Catalyst 3650/3850确实对所消耗的电源进行了更严格的管制,因此,Catalyst 3650/3850上可能会出现Imax错误,因为将同一设备连接到较旧的交换机不会显示任何问题。
确定一个PD究竟在场中吸引了多少能量并不容易。当交换机上的电源控制器检测到端口上消耗了更多电源时,它会关闭端口并通知Cisco IOS® PD已超出最大分配功率。在Cisco IOS中,您可以使用show power inline <interface> detail命令查看每个端口当前消耗的功率。
3850_4#sh power inline Te 3/0/44 detail
Interface: Te3/0/44
Inline Power Mode: auto
Operational status: on
Device Detected: yes
Device Type: Ieee PD
IEEE Class: 3
Discovery mechanism used/configured: Ieee and Cisco
Police: off
Power Allocated
Admin Value: 60.0
Power drawn from the source: 15.0
Power available to the device: 15.0
Actual consumption
Measured at the port: 6.1
Maximum Power drawn by the device since powered on: 6.2
Absent Counter: 0
Over Current Counter: 0
Short Current Counter: 0
Invalid Signature Counter: 0
Power Denied Counter: 0
Power Negotiation Used: IEEE 802.3at LLDP
LLDP Power Negotiation --Sent to PD-- --Rcvd from PD--
Power Type: Type 2 PSE Type 1 PD
Power Source: Primary PSE
Power Priority: low high
Requested Power(W): 12.7 12.7
Allocated Power(W): 12.7 12.7
Four-Pair PoE Supported: Yes
Spare Pair Power Enabled: No
Four-Pair PD Architecture: Shared
此输出中端口上显示的测量值由控制器测量。此信息每隔几秒收集一次,并提供一些有关所消耗功率的指示。使用“最大功率”显示的值似乎有助于排除Imax错误,但遗憾的是,这只是设备最大功率的历史显示。如果发生Imax错误,则当时消耗的功率不会报告回Cisco IOS,也不会显示在Cisco IOS中。
如示例所示,分配给端口的值为15W。这是在接口上编程的截止值。在Cisco Bug ID CSCuy7423之前,Icutoff值在端口上定期编程。每次收到CDP数据包时,都会重新编程该值。在Cisco Bug ID CSCuy74231(在Cisco IOS-XE 3.6.5E和3.7.5或更高版本中修复)之后,此编程已经过优化。这降低了重新编程Icutoff值时“失败”的可能性,这会导致Imax错误。
Icutoff值的编程可通过两个命令显示。通过跟踪记录,可以在跟踪记录中以历史方式收集日志,也可以启用调试以在调试消息出现时记录调试消息。获取此命令的命令如下:
show mgmt-infra trace message platform-mgr-poe
debug platform poe
仅当堆栈中的活动交换机支持PoE时,才能执行show trace命令。否则,首先连接到堆叠中的PoE成员交换机以执行此命令需要此命令:
session switch
*May 20 00:34:04.445:CDP-PA: Packet received from AP2 on interface TenGigabitEthernet3/0/44
**Entry found in cache**
*May 20 00:34:04.445: %IOSXE-7-PLATFORM: MEMBER: 3 process platform_mgr: PoE Info: Dequeued POE SPI msg ver 1 if_id 73003723793629284
num_ports 1 req_id 650 msg_type 20
*May 20 00:34:04.452: %IOSXE-7-PLATFORM: MEMBER: 3 process platform_mgr: PoE Info: E_ILP_SET_CUTOFF if_id 73003723793629284
*May 20 00:34:04.452: %IOSXE-7-PLATFORM: MEMBER: 3 process platform_mgr: PoE Info:port 44 icutoff power 15000
*May 20 00:34:04.452: %IOSXE-7-PLATFORM: MEMBER: 3 process platform_mgr: PoE Info: re_poe_set_icutoff_current port 44 power 15000
*May 20 00:34:04.452: %IOSXE-7-PLATFORM: MEMBER: 3 process platform_mgr: PoE Info: scale factor 22 for power 15000
*May 20 00:34:04.452: %IOSXE-7-PLATFORM: MEMBER: 3 process platform_mgr: PoE Info: POE_SET_CUTOFF_CURRENT_SCALE_FACTOR sent
for port 44 (e:11)
如前所述,诊断Imax错误是一个复杂的过程。出现Imax错误时记录的信息不多。控制器关闭端口,PD通常会丢失所有日志,因为它在消耗比分配的更多电力时正在执行什么操作。现场端口抽取功率的测量不容易,但静态分配功率可以确定。通过静态分配比动态请求的功率多,可以确定PD将消耗多少更多功率,以触发超过Icutoff阈值。可使用命令power inline static max <value>在交换机端口上配置静态最大功耗。
3850_4#sh run int te 3/0/44
interface TenGigabitEthernet3/0/44
power inline static max 20000
end
3850_4#sh power inline te 3/0/44 detail
Interface: Te3/0/44
Inline Power Mode: static
Operational status: on
Device Detected: yes
Device Type: Ieee PD
IEEE Class: 3
Discovery mechanism used/configured: Ieee and Cisco
Police: off
Power Allocated Admin Value: 20.0
Power drawn from the source: 20.0
Power available to the device: 20.0
各种IEEE类都定义了电源使用级别。在PD和PSE之间使用CDP或LLDP进行进一步的功率协商。当你看到Imax错误时,电源协商起着重要作用。PD请求分配多少电源,但也应确保其不超过请求的值。
类PSE PD
0类/默认15.4W 12.95W
1类4.0W 3.84W
2类7.0W 6.49W
3类15.4W 12.95W
4类30.0W 25.50W
根据此表,根据检测到的类,交换机(PSE)允许抽取一定的最大功率。请注意,该标准还定义了PD应该能够消耗的功率。标准为PSE和PD之间的布线使用的电力预算分配。这也突显出,在调查Imax错误时,了解使用哪种类型的电缆以及确定哪些情况下电缆可能比其他情况下电缆更严重非常重要。
除分类外,还使用CDP或LLDP协议完成电源协商。这样,交换机分配的功率可大于或小于类设置的最大功率。
如下例所示,系统会显示PD(本例中为接入点)。在进行电源协商之前,它已分配为类设置的默认15.4W。
3850_4#sh cdp neigh te 3/0/44 detail
-------------------------
Device ID: AP2
Entry address(es):
IPv6 address: FE80::CEEF:48FF:FEC2:1B9B (link-local)
Platform: cisco AIR-CAP3501I-E-K9, Capabilities: Router Trans-Bridge Source-Route-Bridge IGMP
Interface: TenGigabitEthernet3/0/44, Port ID (outgoing port): GigabitEthernet0
Holdtime : 163 sec
Version :
Cisco IOS Software, C3500 Software (AP3G1-K9W8-M), Version 15.3(3)JNB3, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Tue 05-Jan-16 00:44 by prod_rel_team
advertisement version: 2
Duplex: full
Total cdp entries displayed : 1
3850_4#sh power inline te 3/0/44
Interface Admin Oper Power Device Class Max
(Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Te3/0/44 auto on 15.4 AIR-CAP3501I-E-K9 3 60.0
现在,一旦进行电源协商,交换机分配的功率就会减少。请注意,在show cdp neig <if> detail命令的输出中,是请求的各种功率级别。虽然某些设备可能只有一个要求,但有些设备会请求多个功率电平。例如,如果无线接入点不能获得完全供电,则可以打开或关闭无线电。在本例中,PD请求15000或14500 mW。
3850_4#sh cdp neigh te 3/0/44 detail
-------------------------
Device ID: AP2
Entry address(es):
IP address: 10.1.200.2
IPv6 address: FE80::CEEF:48FF:FEC2:1B9B (link-local)
Platform: cisco AIR-CAP3501I-E-K9, Capabilities: Trans-Bridge Source-Route-Bridge IGMP
Interface: TenGigabitEthernet3/0/44, Port ID (outgoing port): GigabitEthernet0
Holdtime : 172 sec
Version :
Cisco IOS Software, C3500 Software (AP3G1-K9W8-M), Version 15.3(3)JNB3, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Tue 05-Jan-16 00:44 by prod_rel_team
advertisement version: 2
Duplex: full
Power drawn: 15.000 Watts
Power request id: 15079, Power management id: 2
Power request levels are: 15000 14500 0 0 0
Management address(es):
IP address: 10.1.200.2
3850_4#sh power inline te 3/0/44 detail
Interface: Te3/0/44
Inline Power Mode: auto
Operational status: on
Device Detected: yes
Device Type: cisco AIR-CAP3501I-
IEEE Class: 3
Discovery mechanism used/configured: Ieee and Cisco
Police: off
Power Allocated
Admin Value: 60.0
Power drawn from the source: 15.0
Power available to the device: 15.0
Actual consumption
Measured at the port: 6.1
Maximum Power drawn by the device since powered on: 6.2
Absent Counter: 0
Over Current Counter: 0
Short Current Counter: 0
Invalid Signature Counter: 0
Power Denied Counter: 0
Power Negotiation Used: CDP
LLDP Power Negotiation --Sent to PD-- --Rcvd from PD--
Power Type: - -
Power Source: - -
Power Priority: - -
Requested Power(W): - -
Allocated Power(W): - -
Four-Pair PoE Supported: Yes
Spare Pair Power Enabled: No
Four-Pair PD Architecture: Shared
使用LLDP而不是CDP的结果相同。当PD通电时,设备会按类接收全部15.4W。
3850_4#sh lldp neighbors te 3/0/44 detail
------------------------------------------------
Local Intf: Te3/0/44
Chassis id: 2c3f.387e.91d0
Port id: Gi0
Port Description: GigabitEthernet0
System Name: AP2.cisco.com
System Description:
Cisco IOS Software, C3500 Software (AP3G1-K9W8-M), Version 15.3(3)JNB3, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Tue 05-Jan-16 00:44 by prod_rel_team
Time remaining: 64 seconds
System Capabilities: B
Enabled Capabilities: B
Management Addresses:
IP: 10.1.200.2
Auto Negotiation - supported, enabled
Physical media capabilities:
1000baseT(FD)
1000baseT(HD)
100base-TX(FD)
100base-TX(HD)
10base-T(FD)
10base-T(HD)
Media Attachment Unit type: 30
Vlan ID: - not advertised
Total entries displayed: 1
3850_4#sh power inline te 3/0/44 detail
Interface: Te3/0/44
Inline Power Mode: auto
Operational status: on
Device Detected: yes
Device Type: Ieee PD
IEEE Class: 3
Discovery mechanism used/configured: Ieee and Cisco
Police: off
Power Allocated
Admin Value: 60.0
Power drawn from the source: 15.4
Power available to the device: 15.4
Actual consumption
Measured at the port: 5.2
Maximum Power drawn by the device since powered on: 5.3
Absent Counter: 0
Over Current Counter: 0
Short Current Counter: 0
Invalid Signature Counter: 0
Power Denied Counter: 0
Power Negotiation Used: None
LLDP Power Negotiation --Sent to PD-- --Rcvd from PD--
Power Type: - -
Power Source: - -
Power Priority: - -
Requested Power(W): - -
Allocated Power(W): - -
Four-Pair PoE Supported: Yes
Spare Pair Power Enabled: No
Four-Pair PD Architecture: N/A
一旦启动,分配就会降低。
3850_4#sh lldp neighbors te 3/0/44 detail
------------------------------------------------
Local Intf: Te3/0/44
Chassis id: 2c3f.387e.91d0
Port id: Gi0
Port Description: GigabitEthernet0
System Name: AP2.cisco.com
System Description:
Cisco IOS Software, C3500 Software (AP3G1-K9W8-M), Version 15.3(3)JNB3, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Tue 05-Jan-16 00:44 by prod_rel_team
Time remaining: 108 seconds
System Capabilities: B
Enabled Capabilities: B
Management Addresses:
IP: 10.1.200.2
Auto Negotiation - supported, enabled
Physical media capabilities:
1000baseT(FD)
1000baseT(HD)
100base-TX(FD)
100base-TX(HD)
10base-T(FD)
10base-T(HD)
Media Attachment Unit type: 30
Vlan ID: - not advertised
PoE+ Power-via-MDI TLV:
Power Pair: Signal
Power Class: Class 3
Power Device Type: Type 1 PD
Power Source: PSE
Power Priority: high
Power Requested: 12700 mW
Power Allocated: 12700 mW
Total entries displayed: 1
3850_4#sh power inline te 3/0/44 detail
Interface: Te3/0/44
Inline Power Mode: auto
Operational status: on
Device Detected: yes
Device Type: Ieee PD
IEEE Class: 3
Discovery mechanism used/configured: Ieee and Cisco
Police: off
Power Allocated
Admin Value: 60.0
Power drawn from the source: 15.0
Power available to the device: 15.0
Actual consumption
Measured at the port: 6.1
Maximum Power drawn by the device since powered on: 6.2
Absent Counter: 0
Over Current Counter: 0
Short Current Counter: 0
Invalid Signature Counter: 0
Power Denied Counter: 0
Power Negotiation Used: IEEE 802.3at LLDP
LLDP Power Negotiation --Sent to PD-- --Rcvd from PD--
Power Type: Type 2 PSE Type 1 PD
Power Source: Primary PSE
Power Priority: low high
Requested Power(W): 12.7 12.7
Allocated Power(W): 12.7 12.7
Four-Pair PoE Supported: Yes
Spare Pair Power Enabled: No
Four-Pair PD Architecture: Share
show power inline <interface> detail命令的输出显示了与CDP显示的协商相比有关的更多信息。CDP和LLDP在电源协商方面还有另一个主要区别。CDP协商端口(15W)上提供的功率量。 但是,使用LLDP时,您会看到PD不协商端口应提供的电源。它要求PD希望拥有的电量。在本例中为12.7W。交换机(PSE)必须补偿布线损失,并为端口分配15W。由于电源协商确实发生,因此确定故障时请求的电源也是关键。了解设备的运行时间以及错误发生时可能发生的事件可以提供有关根本原因的详细信息。例如,IP电话在睡眠后完全打开屏幕,可能会暂时吸引更多电力。
对于Imax错误,很难确定确切原因。在几乎所有情况下,这都是PD耗电量增加的问题,需要与PD供应商合作以调查其耗电量超过其与交换机协商的功率的原因。
此外,还必须研究布线的类型和长度,因为这确实会改变电气特性并影响端口消耗的功率量。此外,还必须调查电源协商并确认设备请求的电源也是分配的电源量。对于LLDP,需要额外预算来布线PD和PSE。在某些情况下,使用静态分配的功率,可以解决Imax错误和/或确定设备在端口上超压的功率量。只有通过功率测量和测试装置,才能确认PD超量其分配的功率量。
在Cisco IOS-XE版本3.6.5和3.7.5及更高版本中,对Imax错误进行了一些改进: