Catalyst 9000交換器中的未知通訊協定捨棄疑難排解
簡介
本文說明Catalyst 9000系列交換器中出現未知通訊協定捨棄的常見原因。
必要條件
需求
思科建議您瞭解以下主題：
- 動態Trunk通訊協定(DTP)
- 連結層探索通訊協定(LLDP)
- Cisco Discovery Protocol(CDP)
- 封裝802.1Q
採用元件
本文中的資訊係根據以下軟體和硬體版本：
- Catalyst 9000 系列交換器
- Cisco IOS® XE
本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路運作中，請確保您瞭解任何指令可能造成的影響。
背景資訊
無法識別訊框的ethertype時，會發生未知的通訊協定捨棄，這表示封裝的通訊協定不受支援或在交換器介面上未設定。此外，幀的目標MAC地址必須是組播控制平面地址，此命令中列出了該地址。
Switch#show mac address-table | include CPU All 0100.0ccc.cccc STATIC CPU All 0100.0ccc.cccd STATIC CPU All 0180.c200.0000 STATIC CPU All 0180.c200.0001 STATIC CPU All 0180.c200.0002 STATIC CPU All 0180.c200.0003 STATIC CPU All 0180.c200.0004 STATIC CPU All 0180.c200.0005 STATIC CPU All 0180.c200.0006 STATIC CPU All 0180.c200.0007 STATIC CPU All 0180.c200.0008 STATIC CPU All 0180.c200.0009 STATIC CPU All 0180.c200.000a STATIC CPU All 0180.c200.000b STATIC CPU All 0180.c200.000c STATIC CPU All 0180.c200.000d STATIC CPU All 0180.c200.000e STATIC CPU All 0180.c200.000f STATIC CPU All 0180.c200.0010 STATIC CPU All 0180.c200.0021 STATIC CPU All ffff.ffff.ffff STATIC CPU
注意：廣播目標MAC地址時，未知協定丟棄不會遞增。
疑難排解
步驟1.確保未知的協定丟棄數量增加。
Switch#show interface ten1/0/5 | include protocol
TenGigabitEthernet1/0/5 is up, line protocol is up (connected)
85 unknown protocol drops
Switch#show interface ten1/0/5 | include protocol
TenGigabitEthernet1/0/5 is up, line protocol is up (connected)
90 unknown protocol drops步驟2.在受影響的介面中配置資料包捕獲，並從01開始匹配目標MAC地址。
Switch#monitor capture port5 interface ten1/0/5 in Switch#monitor capture port5 match mac any 0100.0000.0000 00ff.ffff.ffff Switch#monitor capture port5 buffer size 100
步驟3.啟動資料包捕獲並檢查unknown-protocol-drops計數器。
Switch#monitor capture port5 start
Started capture point : port5
Switch#show interface ten1/0/5 | include protocol
TenGigabitEthernet1/0/5 is up, line protocol is up (connected)
541 unknown protocol drops
步驟4.在幾次未知的協定丟棄後停止資料包捕獲。
Switch#show interface ten1/0/5 | include protocol
TenGigabitEthernet1/0/5 is up, line protocol is up (connected)
544 unknown protocol drops
Switch#monitor capture port5 stop
Capture statistics collected at software:
Capture duration - 68 seconds
Packets received - 38
Packets dropped - 0
Packets oversized - 0
Bytes dropped in asic - 0
Capture buffer will exists till exported or cleared
Stopped capture point : port5步驟5.匯出資料包捕獲內容。
Switch#monitor capture port5 export location flash:drops.pcap Export Started Successfully Switch# Export completed for capture point port5
步驟6.將資料包捕獲傳輸到您的電腦。
Switch#copy flash: ftp: vrf Mgmt-vrf Source filename [drops.pcap]? Address or name of remote host []? 10.10.10.254 Destination filename [drops.pcap]? Writing drops.pcap ! 4024 bytes copied in 0.026 secs (154769 bytes/sec)
步驟7.在Wireshark中開啟資料包捕獲並使用此過濾器(eth.dst包含0100.0ccc.cc || eth.dst包含0180.c200.00),以關注CPU組播地址。
步驟8.轉到統計資訊，然後按一下協定層次。
步驟9.展開通訊協定樹並驗證是否已為這些通訊協定設定交換器介面。任何標籤為Data的內容都會導致未知的協定丟棄，因為ethertype未知。
步驟10.按一下右鍵Data，導航到Apply as Filter，然後按一下Selected以過濾未知協定幀。
步驟11.返回Wireshark的主視窗，確定未知協定的源MAC地址和EtherType。
在本例中，源MAC地址CAFE.CAFE.CAFE導致未知協定丟棄，因為ethertype 0x4343不受支援。
常見問題
本節中的示例基於此網路拓撲圖。
動態Trunk通訊協定(DTP)
如果在禁用DTP的埠上接收到DTP消息，則可能導致未知協定丟棄。您可以在介面配置模式下使用no switchport nonegotiate命令啟用DTP。
C9500-1#show running-config interface Twe1/0/1
interface TwentyFiveGigE1/0/1
description C9300
switchport mode trunk
end
C9300#show running-config interface Gi1/0/1
interface GigabitEthernet1/0/1
description C9500-1
switchport mode trunk
switchport nonegotiate
end
C9300#show interface gi1/0/1 | include unknown
350 unknown protocol drops 連結層探索通訊協定(LLDP)
如果在禁用LLDP的埠上接收到LLDP消息，則也會導致未知協定丟棄。您可以在全域性配置模式下使用lldp run命令啟用LLDP。
C9500-1#show lldp
Global LLDP Information:
Status: ACTIVE
LLDP advertisements are sent every 30 seconds
LLDP hold time advertised is 120 seconds
LLDP interface reinitialisation delay is 2 seconds
C9300#show lldp
% LLDP is not enabled
C9300#show interface gi1/0/1 | include unknown
423 unknown protocol drops Cisco Discovery Protocol(CDP)
同樣，如果在禁用CDP的埠上接收CDP消息，則未知協定丟棄可能會增加。您可以在全域性配置模式下使用cdp run命令來啟用CDP。
C9500-1#show cdp
Global CDP information:
Sending CDP packets every 60 seconds
Sending a holdtime value of 180 seconds
Sending CDPv2 advertisements is enabled
C9300#show cdp
% CDP is not enabled
C9300#show interface gi1/0/1 | include unknown
434 unknown protocol drops 802.1Q報頭中的全零VLAN識別符號
Catalyst 9000系列交換器也在存取連線埠上接收到VLAN ID為0的802.1Q訊框時，將其捨棄。但是，這些資料包不會使未知協定丟棄計數器遞增。在本例中，我們研究為什麼Catalyst 9500交換器無法取得主機192.168.4.22的ARP專案。
C9500-1#ping 192.168.4.22 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.4.22, timeout is 2 seconds: ..... Success rate is 0 percent (0/5) C9500-1#show ip arp vlan 4 Protocol Address Age (min) Hardware Addr Type Interface Internet 192.168.4.1 - ecc0.18a4.b1bf ARPA Vlan4 C9500-1# C9500-1#show running-config interface Twe1/0/5 interface TwentyFiveGigE1/0/5 switchport access vlan 4 switchport mode access load-interval 30 end
步驟1.在連線到終端裝置的介面中開始資料包捕獲。
C9500-1#show monitor capture TAC parameter monitor capture TAC interface TwentyFiveGigE1/0/5 both monitor capture TAC match any monitor capture TAC buffer size 100 circular monitor capture TAC limit pps 1000 C9500-1#monitor capture TAC start Started capture point : TAC
步驟2.嘗試ping終端裝置以生成一些ARP流量。
C9500-1#ping 192.168.4.22 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.4.22, timeout is 2 seconds: ..... Success rate is 0 percent (0/5)
步驟3.停止資料包捕獲。
C9500-1#monitor capture TAC stop
Capture statistics collected at software:
Capture duration - 35 seconds
Packets received - 28
Packets dropped - 0
Packets oversized - 0
Bytes dropped in asic - 0
Capture buffer will exists till exported or cleared
Stopped capture point : TAC
步驟4.注意終端裝置正在傳送ARP應答，在本例中為幀17。
C9500-1#show monitor capture TAC buff brief | include ARP 15 19.402191 ec:c0:18:a4:b1:bf b^F^R ff:ff:ff:ff:ff:ff ARP 60 Who has 192.168.4.22? Tell 192.168.4.1 17 21.347022 fe:af:ea:fe:af:ea b^F^R ec:c0:18:a4:b1:bf ARP 60 192.168.4.22 is at fe:af:ea:fe:af:ea
步驟5.注意ARP應答是使用VLAN ID 0封裝在802.1Q報頭中的。
C9500-1#show monitor capture TAC buff detailed | begin Frame 17
Frame 17: 60 bytes on wire (480 bits), 60 bytes captured (480 bits) on interface 0
<output omitted>
Ethernet II, Src: fe:af:ea:fe:af:ea (fe:af:ea:fe:af:ea), Dst: ec:c0:18:a4:b1:bf (ec:c0:18:a4:b1:bf)
Destination: ec:c0:18:a4:b1:bf (ec:c0:18:a4:b1:bf)
Address: ec:c0:18:a4:b1:bf (ec:c0:18:a4:b1:bf)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Source: fe:af:ea:fe:af:ea (fe:af:ea:fe:af:ea)
Address: fe:af:ea:fe:af:ea (fe:af:ea:fe:af:ea)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
Type: 802.1Q Virtual LAN (0x8100)
802.1Q Virtual LAN, PRI: 0, DEI: 0, ID: 0
000. .... .... .... = Priority: Best Effort (default) (0)
...0 .... .... .... = DEI: Ineligible
.... 0000 0000 0000 = ID: 0
Type: ARP (0x0806)
Padding: 0000000000000000000000000000
Address Resolution Protocol (reply)
Hardware type: Ethernet (1)
Protocol type: IPv4 (0x0800)
Hardware size: 6
Protocol size: 4
Opcode: reply (2)
Sender MAC address: fe:af:ea:fe:af:ea (fe:af:ea:fe:af:ea)
Sender IP address: 192.168.4.22
Target MAC address: ec:c0:18:a4:b1:bf (ec:c0:18:a4:b1:bf)
Target IP address: 192.168.4.1步驟6.匯出資料包捕獲內容。
C9500-1#monitor capture TAC export location flash:ARP.pcap Export Started Successfully
步驟7.使用Packet Tracer工具確定交換機對Packet 17執行的操作。
C9500-1#show platform hardware fed active forward interface Twe1/0/5 pcap flash:ARP.pcap number 17 data Show forward is running in the background. After completion, syslog will be generated. C9500-1# *Sep 29 17:45:29.091: %SHFWD-6-PACKET_TRACE_DONE: R0/0: fed: Packet Trace Complete: Execute (show platform hardware fed switch <> forward last summary|detail) *Sep 29 17:45:29.091: %SHFWD-6-PACKET_TRACE_FLOW_ID: R0/0: fed: Packet Trace Flow id is 6881284
步驟8.顯示Packet Tracer結果。
C9500-1#show platform hardware fed active forward last summary
Input Packet Details:
###[ Ethernet ]###
dst = ec:c0:18:a4:b1:bf
src=fe:af:ea:fe:af:ea
type = 0x8100
###[ 802.1Q ]###
prio = 0
id = 0
vlan = 0
type = 0x806
###[ ARP ]###
hwtype = 0x1
ptype = 0x800
hwlen = 6
plen = 4
op = is-at
hwsrc=fe:af:ea:fe:af:ea
psrc=192.168.4.22
hwdst = ec:c0:18:a4:b1:bf
pdst = 192.168.4.1
###[ Padding ]###
load = '00 00 00 00 00 00 00 00 00 00 00 00 00 00'
<output omitted>
Packet DROPPED
Catch-all for phf.finalFdPresent==1.
附註：資料包被丟棄，因為它包括VLAN ID 0。
有兩種方法可以防止此類丟棄。
選項 1:使用命令switchport voice vlan dot1p。這樣，通過vlan 0接收的幀將分配給接入vlan。
interface TwentyFiveGigE1/0/5 switchport access vlan 4 switchport mode access switchport voice vlan dot1p load-interval 30
選項 2:將介面配置為中繼埠。這樣，通過vlan 0接收的幀將分配給本徵vlan。
interface TwentyFiveGigE1/0/5 switchport trunk native vlan 4 switchport mode trunk load-interval 30 end
附註：這在Profinet裝置上很常見。
相關缺陷
- 如需詳細資訊，請參閱Cisco錯誤ID CSCwe8812。
相關資訊
修訂記錄
| 修訂 | 發佈日期 | 意見 |
|---|---|---|
1.0 |
24-Aug-2025
|
初始版本 |
意見