Cisco设备ATM接口和SNMP问题

deeperpurple

一年多以前用SNMP获取ATM接口流量遇到流量统计问题，刚好在netexpert上看到happywolf发问，留此存照以备后用。原连接地址
http://www.netexpert.cn/thread-12008-1-1.html
1、Cisco 路由器上show atm子接口无法看到流量统计，用snmp可以获取
ATM5/1/0.111 is up, line protocol is up
  Hardware is cyBus ENHANCED ATM PA, address is 0005.0001.d8a8 (bia 0005.0001.d8a8)
  Description: ATM To ***
  Internet address is **.0.241.41/30
  MTU 1500 bytes, BW 2048 Kbit, DLY 80 usec, rely 255/255, load 5/255
  Encapsulation ATM
  759213379 packets input, 123356344845 bytes
  346337009 packets output,112582465918 bytes
  3714297 OAM cells input, 3715541 OAM cells output
  AAL5 CRC errors : 6036
  AAL5 SAR Timeouts : 0
  AAL5 Oversized SDUs : 0
有什么方法可以通过show命令看到该接口的流量么？
比如  5 minute input rate 4551000 bits/sec, 1917 packets/sec
  5 minute output rate 3151000 bits/sec, 1094 packets/sec
解答：
ATM接口上Interface及VC接口上统计排错
文中明确说明：
Note: Calculated bit rates are available only on a main interface.
2、为什么用SNMP可以获取到子接口流量
解答：
Implementing Network Management on ATM Interfaces
Interface Statistics
ATM comprises a three-layer stack: an ATM adaptation layer (AAL), an
ATM layer, and a physical layer, such as Sonet or T1. Each layer counts
packets and octets in a slightly different way. Correspondingly, an ATM
interface appears multiple times in the ifTable, with these entries:
      1 Physical layer, such as Sonet
      2 ATM cell layer
      3 AAL5 layer
      4 Any sub-interfaces (depending on the Cisco IOS Software level)
下面这是那里面的例子，获取接口标识；
# snmpwalk -c public 192.168.1.1 ifType
IF-MIB::ifType.1 = INTEGER: sonet(39)
IF-MIB::ifType.2 = INTEGER: ethernetCsmacd(6)
IF-MIB::ifType.3 = INTEGER: atm(37)
IF-MIB::ifType.4 = INTEGER: atmSubInterface(134)
IF-MIB::ifType.5 = INTEGER: aal5(49)
IF-MIB::ifType.6 = INTEGER: aal5(49)
IF-MIB::ifType.7 = INTEGER: other(1)
IF-MIB::ifType.8 = INTEGER: atmSubInterface(134)
IF-MIB::ifType.9 = INTEGER: aal5(49)
IF-MIB::ifType.10 = INTEGER: atmSubInterface(134)
IF-MIB::ifType.11 = INTEGER: aal5(49)
MRTG画图的基本实质是用获取一些SNMP变量的值，所以这个文章里还这样说，针对ATM接口，一些SNMP变量是无法支持或者部分支持，如下：
These variables are not maintained for the atmSubInterface layer due to
the lack of cell-layer counters in the drivers of current interfaces:
      ifInOctets, ifOutOctets, ifHCInOctets, ifHCOutOctets
The counters may be implemented if the drivers of new ATM Port Adapters (PAs) provide cell-layer counters.
These variables are not maintained for the atmSubInterface layer because they are not maintained at the ATM layer:
      ifInUcastPkts, ifInNUcastPkts,ifOutUcastPkts, ifOutNUcastPkts
      ifInBroadcastPkts, ifOutBroadcastPkts
      ifInMulticastPkts, ifOutMulticastPkts
      ifInDiscards
      ifHCInUcastPkts, ifHCInMulticastPkts, ifHCInBroadcastPkts,
      ifHCOutUcastPkts, ifHCOutMulticastPkts, ifHCOutBroadcastPkts
These variables are not updated at the atmSubInterface layer because it
is not possible to gather these statistics on a per-VC basis:
      ifInErrors,ifOutErrors
      ifInUnknownProtos
      ifOutDiscards
      ifOutQLen
These variables are hardwired to FALSE for ATM subinterfaces:
      ifPromiscuousMode
      ifConnectorPresent
另外，如何使用SNMP计算带宽利用率，有三个基本参数IfInOctets,IfOutOctets,IfSpeed，参考连接
How to Calculate Bandwidth Utilization with SNMP
所以对于ATM Subinterface，有OID能够标识这些子接口，自然能够通过SNMP Read的方式获取其Value，进而在MRTG里画出图来。
               
               
               

本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/26393/showart_201094.html