SNMP计数器问题
问：我应该将哪个MIB用于接口计数器？
A.基于SNMP的接口管理基于两个表：ifTable（仅限注册用户）及其扩展名，ifxtable（仅限注册用户）在RFC1213 / RFC2233中描述。接口可以有多个层，这取决于介质，每个子层由表中的一个单独的行表示。ifStackTable（仅限注册用户）中描述了较高层和较低层之间的关系。ifTable为入站和出站八位字节定义32位计数器（ifInOctets（仅限注册用户）/ ifOutOctets），数据包（ ifInUcastPkts（仅限注册用户）/ ifOutUcastPkts（仅限注册用户），ifInNUcastPkts（仅限注册用户）/ ifOutNUcastPkts（仅限注册用户）），错误和丢弃。ifXTable提供类似的64位计数器，也称为高容量（HC）计数器：ifHCInOctets（仅限注册用户）/ ifHCOutOctets（仅限注册用户）和ifHCInUcastPkts（已注册） 仅限客户）/ ifHCOutUcastPkts（仅限注册用户）。
问：什么时候应该使用64位计数器？
随着网络媒体速度的增加，32位计数器包装的最小时间减少。例如，一个10 Mbps的背对背全尺寸数据包流导致ifInOctets在57分钟内完成包装。在100 Mbps时，最小环绕时间为5.7分钟，在1 Gbps时，最小环绕时间为34秒。注意： SNMP计数器换行，命令行界面（CLI）计数器不换行。对于以每秒20,000,000（2000万）位或更少的速度运行的接口，必须使用32位字节和数据包计数器。对于运行速度超过每秒2000万比特且速度低于每秒650,000,000比特的接口，必须使用32位数据包计数器和64位八位字节计数器。对于以650,000,000位/秒或更快速运行的接口，必须使用64位数据包和八位字节计数器。相应地，CiscoIOS®软件不支持64位计数器，接口速度低于20 Mbps。这意味着10 Mb以太网端口不支持64位计数器，只有100 Mb快速以太网和其他高速端口支持64位计数器。
问：查询64位计数器需要哪个版本的SNMP？
A.查询64位计数器需要SNMPv2C或SNMPv3。SNMPv1不支持64位计数器。请注意，ifInOctets = .1.3.6.1.2.1.2.2.1.10是32位计数器，而64位版本是ifHCInOctets = .1.3.6.1.2.1.31.1.1.1.6。例如：Catalyst 5000使用HP OpenView snmpget，默认为SNMPv1#snmpget -c public 14.32.5.18 ifName.1 ifMIB.ifMIBObjects.ifXTable.ifXEntry.ifName.1 DISPLAY STRING-（ascii）sc0使用SNMPv1查询，HP OpenView snmpget的默认值#snmpget -c public 14.32.5.18 ifHCInOctets.1 snmpget代理报告了变量＃1的错误。 .iso.org.dod.internet.mgmt.mib-2.ifMIB.ifMIBObjects.ifXTable.ifXEntry。 ifHCInOctets.1 SNMP变量不存在或访问被拒绝。与SNMPv2C相同的查询#snmpget -v 2c -c public 14.32.5.18 ifHCInOctets.1 ifMIB.ifMIBObjects.ifXTable.ifXEntry.ifHCInOctets.1 Counter64 622366215
问：哪些Cisco设备实现64位SNMP计数器，尤其是IF-MIB？
答：这些思科设备实现了64位SNMP计数器：注意： 您必须是注册用户，并且您必须登录才能访问Cisco Bug ID链接并查看详细的错误信息。
问：ifInOctets和ifOutOctets SNMP计数器是否与show interface In / Out计数器相同？
答：是的，但仅在启动时启用SNMP时。如果启动Cisco设备，然后启用SNMP，则SNMP计数器从0开始。它们不会自动从CLI输出中获取其值。
问：ifInOctets和ifOutOctets计数器是否包括成帧开销（点对点协议，高级数据链路控制）？
答：是的。
问：在异步传输模式接口上，计数器是否包含单元头？
A.异步传输模式（ATM）计数器不包括ATM开销（信元标头和AAL5填充）。
问：为什么SNMP计数器不会返回与CLI show命令相同的数字？
“3.2.3.3。反击这个应用程序范围的类型表示一个非负整数，当它环绕并从零开始再次增加时，它会单调增加直到达到最大值。此备忘录指定计数器的最大值为2 ^ 32-1（小数为4294967295）。“没有重新加载设备的方法，无法将SNMP计数器重置为零。CLI show命令的计数器输出可以在接口上重置，因为SNMP限制不存在。MIB-2中定义的原始接口计数器是32位计数器。对于10 Mbps接口，32位计数器理论上可以在57分钟内完成。很容易避免这么长时间的不连续性。但对于100 Mbps，最小理论包装时间为5.7分钟。对于1 Gbps接口，它降至34秒。这些时间用于传输背对背的全尺寸数据包，这是理论上的理想选择。即便如此，界面速度越高，越难以避免错过反包装。作为此问题的解决方案，SNMPv2 SMI为64位计数器定义了一个新的对象类型counter64。因此，在RFC 1573中 定义的扩展接口表（ifxTable）中定义了几个新的64位计数器（后来被RFC 2233取代）
ifHCInOctets （.1.3.6.1.2.1.31.1.1.1.6） ifHCOutOctets （1.3.6.1.2.1.31.1.1.1.10） ifHCInUcastPkts （.1.3.6.1.2.1.31.1.1.1.7） ifHCOutUcastPkts （.1.3.6.1.2.1.31.1.1.1.11） ifHCInMulticastPkts （.1.3.6.1.2.1.31.1.1.1.8） ifHCOutMulticastPkts （.1.3.6.1.2.1.31.1.1.1.12） ifHCInBroadcastPkts （.1.3.6.1.2.1.31.1.1.1.9） ifHCOutBroadcastPkts （.1.3.6.1.2.1.31.1.1.1.13） 虽然64位计数器的基本支持已写入Cisco IOS软件版本11.3，该版本从Cisco IOS软件版本12.0开始，但仅限于HCInOctets（.1.3.6.1.2.1.31.1.1.1.6）和ifHCOutOctets（1.3.6.1.2.1） .31.1.1.1.10）仅针对ATM LANE LEC子接口实现。对于Catalyst工作组交换机，版本3.1中已实现64位计数器支持。注意： 必须使用SNMPv2c或SNMPv3协议才能检索任何计数器64对象。
SNMP计数器和show命令等效问题
问：Cisco路由器为以下SNMP MIB变量做了什么：ifInOctets，ifInUcastPkts，ifInNUcastPkts，ifInDiscards，ifInErrors，ifInUnknownProtos，ifOutOctets，ifOutUcastPkts，ifOutNUcastPkts，ifOutDiscards，ifOutErrors和ifOutQLen？
ifInNUcastPkts（.1.3.6.1.2.1.2.2.1.12） 这些是入站广播和多播数据包的计数。 ifInDiscards（.1.3.6.1.2.1.2.2.1.13） 这些被视为无缓冲区，如show interfaces命令中所反映的那样。 ifInErrors（.1.3.6.1.2.1.2.2.1.14） 这些是show interfaces命令中反映的所有输入错误的计数。 ifInUnknownProtos（.1.3.6.1.2.1.2.2.1.15） 这些被视为未分类的错误。 ifOutOctets（.1.3.6.1.2.1.2.2.1.16） 这些是接口输出的字节数的计数，如show interfaces命令所示。 ifOutUcastPkts（.1.3.6.1.2.1.2.2.1.17） 这些是出站广播和多播数据包的计数。 ifOutDiscards（.1.3.6.1.2.1.2.2.1.19） 这些被计为输出丢弃，如show interfaces命令所示。 ifOutErrors（.1.3.6.1.2.1.2.2.1.20） 这些被计为输出错误，如show interfaces命令中所示。 ifOutQLen（.1.3.6.1.2.1.2.2.1.21） 这是允许在输出队列上的数据包数，如show interfaces命令所示。 之前列出的不显示它们出现在show interfaces中的变量在除SNMP之外的任何地方都不可用。例子
此示例使用与Cisco IOS软件版本12.2（2）T1一起运行的3640。使用的只读（RO）团体字符串是公共的，并且使用的读写（RW）团体字符串是私有的。有关如何在设备上配置SNMP社区字符串的详细信息，请参阅如何配置SNMP社区字符串。此输出是启用模式下执行的show ip interface brief命令的典型输出：
3600#show ip interface brief
Interface IP-Address OK? Method Status Prol
BRI0/0 unassigned YES NVRAM administratively down dow
FastEthernet0/0 172.16.99.20 YES NVRAM up up
Serial0/0 unassigned YES NVRAM down dow
Serial0/0.1 unassigned YES unset down dow
BRI0/0:1 unassigned YES unset administratively down dow
BRI0/0:2 unassigned YES unset administratively down dow
Serial0/1 unassigned YES NVRAM administratively down dow
ATM1/0 unassigned YES NVRAM down dow
ATM1/0.109 10.164.0.46 YES NVRAM down dow
Virtual-Template1 99.99.99.99 YES NVRAM down dow
Loopback0 10.1.10.1 YES NVRAM up up
Loopback1 unassigned YES NVRAM up up
Loopback101 3.3.3.3 YES NVRAM administratively down dow
Loopback200 4.4.4.14 YES NVRAM administratively down dow
Loopback201 4.4.4.18 YES NVRAM administratively down dow 此输出是前一个路由器的描述（.1.3.6.1.2.1.2.2.1.2）的MIB对象，它是包含接口信息的文本字符串。这给出了获得的接口名称和描述，它使用以前的CLI命令输出。IFNAME（.1.3.6.1.2.1.31.1.1.1.1）也可以使用，但ifDescr给出的名称，其中，沿所述接口描述IFNAME只给出了接口名。
snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.2 interfaces.ifTable.ifEntry.ifDescr.1 = ATM1/0 interfaces.ifTable.ifEntry.ifDescr.2 = BRI0/0 interfaces.ifTable.ifEntry.ifDescr.3 = FastEthernet0/0 interfaces.ifTable.ifEntry.ifDescr.4 = Serial0/0 interfaces.ifTable.ifEntry.ifDescr.5 = BRI0/0:1 interfaces.ifTable.ifEntry.ifDescr.6 = BRI0/0:2 interfaces.ifTable.ifEntry.ifDescr.7 = Serial0/1 interfaces.ifTable.ifEntry.ifDescr.8 = Null0 interfaces.ifTable.ifEntry.ifDescr.10 = Foreign Exchange Office 2/0/0 interfaces.ifTable.ifEntry.ifDescr.11 = Foreign Exchange Office 2/0/1 interfaces.ifTable.ifEntry.ifDescr.12 = recEive And transMit 3/0/0 interfaces.ifTable.ifEntry.ifDescr.13 = recEive And transMit 3/0/1 interfaces.ifTable.ifEntry.ifDescr.14 = Loopback0 interfaces.ifTable.ifEntry.ifDescr.15 = Loopback1 interfaces.ifTable.ifEntry.ifDescr.16 = Loopback101 interfaces.ifTable.ifEntry.ifDescr.17 = Loopback200 interfaces.ifTable.ifEntry.ifDescr.18 = Loopback201 interfaces.ifTable.ifEntry.ifDescr.19 = Serial0/0.1 interfaces.ifTable.ifEntry.ifDescr.20 = ATM1/0.109-atm subif interfaces.ifTable.ifEntry.ifDescr.21 = ATM1/0.109-aal5 layer interfaces.ifTable.ifEntry.ifDescr.22 = Virtual-Template1 interfaces.ifTable.ifEntry.ifDescr.23 = Voice Encapsulation (POTS) Peer: 1 interfaces.ifTable.ifEntry.ifDescr.24 = Voice Over IP Peer: 2 interfaces.ifTable.ifEntry.ifDescr.25 = Voice Encapsulation (POTS) Peer: 111 interfaces.ifTable.ifEntry.ifDescr.26 = Voice Over IP Peer: 222 interfaces.ifTable.ifEntry.ifDescr.27 = Voice Over IP Peer: 1234 interfaces.ifTable.ifEntry.ifDescr.28 = Voice Over IP Peer: 300000 interfaces.ifTable.ifEntry.ifDescr.29 = Voice Over FR Peer: 3 interfaces.ifTable.ifEntry.ifDescr.30 = Voice Over IP Peer: 99 interfaces.ifTable.ifEntry.ifDescr.31 = Voice Encapsulation (POTS) Peer: 9 interfaces.ifTable.ifEntry.ifDescr.32 = BRI0/0-Physical interfaces.ifTable.ifEntry.ifDescr.33 = BRI0/0-Signaling interfaces.ifTable.ifEntry.ifDescr.34 = BRI0/0:1-Bearer Channel interfaces.ifTable.ifEntry.ifDescr.35 = BRI0/0:2-Bearer Channel
- ifInDiscards (.1.3.6.1.2.1.2.2.1.13):
该ifInDiscards是该路由器的所有接口零。如果将此与show interfaces fastEthernet 0/0命令的CLI结果进行比较，则会确认结果：snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.13 interfaces.ifTable.ifEntry.ifInDiscards.1 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.2 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.3 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.4 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.5 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.6 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.7 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.8 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.10 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.11 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.12 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.13 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.14 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.15 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.16 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.17 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.18 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.19 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.20 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.21 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.22 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.23 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.24 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.25 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.26 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.27 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.28 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.29 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.30 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.31 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.32 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.33 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.34 = Counter32: 0 interfaces.ifTable.ifEntry.ifInDiscards.35 = Counter32: 0
3600#show interfaces fastEthernet 0/0 FastEthernet0/0 is up, line protocol is up Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81) Description: testme Internet address is 172.16.99.20/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 323 drops 5 minute input rate 1000 bits/sec, 2 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 1767411 packets input, 178272010 bytes Received 1161500 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog 0 input packets with dribble condition detected 7146925 packets output, 765049281 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 461 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
ifInErrors (.1.3.6.1.2.1.2.2.1.14):
snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.14
interfaces.ifTable.ifEntry.ifInErrors.1 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.2 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.3 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.4 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.5 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.6 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.7 = Counter32: 1
interfaces.ifTable.ifEntry.ifInErrors.8 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.10 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.11 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.12 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.13 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.14 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.15 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.16 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.17 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.18 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.19 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.20 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.21 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.22 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.23 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.24 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.25 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.26 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.27 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.28 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.29 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.30 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.31 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.32 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.33 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.34 = Counter32: 0
interfaces.ifTable.ifEntry.ifInErrors.35 = Counter32: 0
此输出显示接口只有一个输入错误
interfaces.ifTable.ifEntry.ifInErrors.7 = Counter32：1。
为了确定它是哪个接口，将其与上面ifDescr的输出进行比较，这表明它来自interfaces.ifTable.ifEntry.ifDescr.7 = Serial0 / 1。现在在启用模式下执行show interfaces serial 0/1命令以验证以前的结果：
3600#show interfaces serial 0/1 Serial0/1 is administratively down, line protocol is down Hardware is DSCC4 Serial Description: atm-dxi test MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ATM-DXI, loopback not set Keepalive not set Last input never, output never, output hang never Last clearing of "show interface" counters 1w1d Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 1 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 1 abort 0 packets output, 0 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 output buffer failures, 0 output buffers swapped out 0 carrier transitions DCD=down DSR=down DTR=down RTS=down CTS=down
- ifOutOctets (.1.3.6.1.2.1.2.2.1.16):
snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.16 interfaces.ifTable.ifEntry.ifOutOctets.1 = Counter32: 98 interfaces.ifTable.ifEntry.ifOutOctets.2 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.3 = Counter32: 765470674 interfaces.ifTable.ifEntry.ifOutOctets.4 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.5 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.6 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.7 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.8 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.10 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.11 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.12 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.13 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.14 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.15 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.16 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.17 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.18 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.19 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.20 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.21 = Counter32: 98 interfaces.ifTable.ifEntry.ifOutOctets.22 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.23 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.24 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.25 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.26 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.27 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.28 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.29 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.30 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.31 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.32 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.33 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.34 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutOctets.35 = Counter32: 0
如果将先前的结果与ifDescr的输出进行比较，则表明：- interfaces.ifTable.ifEntry.ifOutOctets.1 = Counter32：98对应interfaces.ifTable.ifEntry.ifDescr.1 = ATM1 / 0
- interfaces.ifTable.ifEntry.ifOutOctets.3 = Counter32：765470674对应interfaces.ifTable.ifEntry.ifDescr.3 = FastEthernet0 / 0
- interfaces.ifTable.ifEntry.ifOutOctets.21 = Counter32：98对应interfaces.ifTable.ifEntry.ifDescr.21 = ATM1 / 0.109-aal5 layer
3600#show interfaces atM 1/0 ATM1/0 is down, line protocol is down Hardware is RS8234 ATMOC3 MTU 4470 bytes, sub MTU 4470, BW 155000 Kbit, DLY 80 usec, reliability 5/255, txload 1/255, rxload 1/255 Encapsulation ATM, loopback not set Encapsulation(s): AAL5 1024 maximum active VCs, 1 current VCCs VC idle disconnect time: 300 seconds Last input never, output 1w1d, output hang never Last clearing of "show interface" counters never Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0 Queueing strategy: None 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 2 packets output, 98 bytes, 0 underruns 0 output errors, 0 collisions, 2 interface resets 0 output buffer failures, 0 output buffers swapped out 3600#show interfaces fastEthernet 0/0 FastEthernet0/0 is up, line protocol is up Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81) Description: testme Internet address is 172.16.99.20/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 323 drops 5 minute input rate 2000 bits/sec, 3 packets/sec 5 minute output rate 1000 bits/sec, 1 packets/sec 1772214 packets input, 178767841 bytes Received 1164210 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog 0 input packets with dribble condition detected 7149179 packets output, 765450524 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 461 deferred 0 lost carrier, 0 no carrier0 output buffer failures, 0 output buffers swapped out
在输出ifOutOctets不匹配的CLI的输出显示接口，快速以太网0/0命令，却是相似的。这是因为轮询接口和执行CLI命令时可能会有延迟。
3600#show interfaces atM 1/0.109 ATM1/0.109 is down, line protocol is down Hardware is RS8234 ATMOC3 Description: pvc Internet address is 10.164.0.46/30 MTU 4470 bytes, BW 2250 Kbit, DLY 80 usec, reliability 5/255, txload 1/255, rxload 1/255 Encapsulation ATM 0 packets input, 0 bytes 2 packets output,98 bytes 0 OAM cells input, 77093 OAM cells output AAL5 CRC errors : 0 AAL5 SAR Timeouts : 0 AAL5 Oversized SDUs : 0 AAL5 length violation : 0 AAL5 CPI Error : 0
- ifOutDiscards (.1.3.6.1.2.1.2.2.1.19):
所有接口的ifOutDiscards为零。以show interfaces fastEthernet 0/0命令为例，该命令产生以下结果：snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.19 interfaces.ifTable.ifEntry.ifOutDiscards.1 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.2 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.3 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.4 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.5 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.6 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.7 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.8 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.10 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.11 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.12 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.13 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.14 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.15 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.16 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.17 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.18 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.19 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.20 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.21 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.22 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.23 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.24 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.25 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.26 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.27 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.28 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.29 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.30 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.31 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.32 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.33 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.34 = Counter32: 0 interfaces.ifTable.ifEntry.ifOutDiscards.35 = Counter32: 0
53600#show interfaces fastEthernet 0/0 FastEthernet0/0 is up, line protocol is up Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81) Description: testme Internet address is 172.16.99.20/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 323 drops 5 minute input rate 1000 bits/sec, 2 packets/sec 5 minute output rate 1000 bits/sec, 1 packets/sec 1774581 packets input, 179005552 bytes Received 1165620 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog 0 input packets with dribble condition detected 7150259 packets output, 765645035 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 461 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
ifOutErrors (.1.3.6.1.2.1.2.2.1.20):
snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.20
interfaces.ifTable.ifEntry.ifOutErrors.3 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.4 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.5 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.6 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.7 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.8 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.10 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.11 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.12 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.13 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.14 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.15 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.16 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.17 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.18 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.19 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.20 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.21 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.22 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.23 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.24 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.25 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.26 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.27 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.28 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.29 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.30 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.31 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.32 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.33 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.34 = Counter32: 0
interfaces.ifTable.ifEntry.ifOutErrors.35 = Counter32: 0
所有接口的ifOutErrors均为零。以show interfaces fastEthernet 0/0命令为例，该命令产生以下结果：
3600#show interfaces fastEthernet 0/0 FastEthernet0/0 is up, line protocol is up Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81) Description: testme Internet address is 172.16.99.20/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 323 drops 5 minute input rate 0 bits/sec, 1 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 1776187 packets input, 179154616 bytes Received 1166778 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog 0 input packets with dribble condition detected 7150781 packets output, 765744231 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 461 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
ifOutQLen (.1.3.6.1.2.1.2.2.1.21):
snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.21
interfaces.ifTable.ifEntry.ifOutQLen.1 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.2 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.3 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.4 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.5 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.6 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.7 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.8 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.10 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.11 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.12 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.13 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.14 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.15 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.16 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.17 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.18 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.19 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.20 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.21 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.22 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.23 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.24 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.25 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.26 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.27 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.28 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.29 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.30 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.31 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.32 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.33 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.34 = Gauge32: 0
interfaces.ifTable.ifEntry.ifOutQLen.35 = Gauge32: 0
所有接口的ifOutQLen都为零。以show interfaces fastEthernet 0/0命令为例：
3600#show interfaces fastEthernet 0/0 FastEthernet0/0 is up, line protocol is up Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81) Description: testme Internet address is 172.16.99.20/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) Full-duplex, 100Mb/s, 100BaseTX/FX ARP type: ARPA, ARP Timeout 04:00:00 Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 323 drops 5 minute input rate 0 bits/sec, 1 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 1776912 packets input, 179225431 bytes Received 1167240 broadcasts, 0 runts, 0 giants, 0 throttles 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored 0 watchdog 0 input packets with dribble condition detected 7151102 packets output, 765796341 bytes, 0 underruns(0/0/0) 0 output errors, 0 collisions, 1 interface resets 0 babbles, 0 late collision, 461 deferred 0 lost carrier, 0 no carrier 0 output buffer failures, 0 output buffers swapped out
问：show interfaces语句没有缓冲区和输入队列丢弃之间的关系是什么？为什么SNMP的inDiscards 没有缓冲计数而没有输入队列丢弃，而SNMP的outDiscards确实给输出队列丢弃了？
A.该locIfInputQueueDrops / ifInDiscards比locIfOutputQueueDrops / ifOutDiscards工作方式不同。ifInDiscards计算因缺少系统资源（如缓冲区）而丢弃的数据包数。这通常是locIfInputQueueDrops的一个子集。您经常会看到locIfInputQueueDrops = ifInDiscards。但是，locIfInputQueueDrops还会计算因为达到输入队列限制而丢弃的数据包数。通常，您会看到locIfInputQueueDrops> ifInDiscards。摘要locIfInputQueueDrops =队列限制丢弃+无缓冲区丢弃ifInDiscards =无缓冲区丢弃（并且是locIfInputQueueDrops的子集）locIfOutputQueueDrops和ifOutDiscards在计算相同事件时始终相等。这些事件达到输出队列限制，并且当数据包从一个接口快速切换到另一个接口时没有硬件tx缓冲区。以前的MIB对象的OID是：
来自OLD-CISCO-INTERFACES-MIB（仅限注册用户） 来自RFC1213-MIB（仅限注册用户） locIfInputQueueDrops = .1.3.6.1.4.1.9.2.2.1.1.26 ifInDiscards = .1.3.6.1.2.1.2.2.1.13 locIfOutputQueueDrops = .1.3.6.1.4.1.9.2.2.1.1.27 ifOutDiscards = .1.3.6.1.2.1.2.2.1.19 问：我可以在路由器上轮询没有缓冲区吗？
答：是的。您可以轮询ifInDiscards以便轮询没有缓冲区。问：如何在路由器上轮询队列限制丢弃？
https://www.cisco.com/c/en/us/support/docs/ip/simple-network-management-protocol-snmp/26007-faq-snmpcounter.html答：使用SNMP，show interfaces命令无法打破输入丢弃的各个元素。考虑有关输出丢弃计数器内容的新信息：输入丢弃=队列限制丢弃+限制丢弃+ SMT队列完全丢弃+ RSRB丢弃+无缓冲丢弃此外，即使清除了接口，也不会清除SNMP计数器。
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