Examples–Checking the Network Status (System Administration Guide: Network Services)

System Administration Guide: Network Services

Examples–Checking the Network Status

The following example shows output from the netstat -i command, which displays the state of the interfaces that are used for TCP/IP traffic.

$ netstat -i
Name  Mtu  Net/Dest    Address      Ipkts  Ierrs Opkts  Oerrs Collis Queue
lo0   8232 software    localhost     1280   0     1280     0       0    0
eri0   1500 loopback    venus      1628480   0   347070    16   39354    0

This display shows the number of packets that a machine has transmitted and has received on each interface. A machine with active network traffic should show both Ipkts and Opkts continually increasing.

Calculate the network collisions rate by dividing the number of collision counts (Collis) by the number of out packets (Opkts). In the previous example, the collision rate is 11 percent. A network-wide collision rate that is greater than 5 to 10 percent can indicate a problem.

Calculate the error rate for the input packets by dividing the number of input errors by the total number of input packets (Ierrs/Ipkts). The error rate for the output packets is the number of output errors divided by the total number of output packets (Oerrs/Opkts). If the input error rate is high, at over 0.25 percent, the host might be dropping packets.

The following example shows output from the netstat -s command, which displays the per-protocol statistics for the UDP, TCP, ICMP, and IGMP protocols.

UDP
    udpInDatagrams      =196543    udpInErrors         =     0
    udpOutDatagrams     =187820
 
TCP
    tcpRtoAlgorithm     =     4    tcpRtoMin           =   200
    tcpRtoMax           = 60000    tcpMaxConn          =    -1
    tcpActiveOpens      = 26952    tcpPassiveOpens     =   420
    tcpAttemptFails     =  1133    tcpEstabResets      =     9
    tcpCurrEstab        =    31    tcpOutSegs          =3957636
    tcpOutDataSegs      =2731494   tcpOutDataBytes     =1865269594
    tcpRetransSegs      = 36186    tcpRetransBytes     =3762520
    tcpOutAck           =1225849   tcpOutAckDelayed    =165044
    tcpOutUrg           =     7    tcpOutWinUpdate     =   315
    tcpOutWinProbe      =     0    tcpOutControl       = 56588
    tcpOutRsts          =   803    tcpOutFastRetrans   =   741
    tcpInSegs           =4587678
    tcpInAckSegs        =2087448   tcpInAckBytes       =1865292802
    tcpInDupAck         =109461    tcpInAckUnsent      =     0
    tcpInInorderSegs    =3877639   tcpInInorderBytes   =-598404107
    tcpInUnorderSegs    = 14756    tcpInUnorderBytes   =17985602
    tcpInDupSegs        =    34    tcpInDupBytes       = 32759
    tcpInPartDupSegs    =   212    tcpInPartDupBytes   =134800
    tcpInPastWinSegs    =     0    tcpInPastWinBytes   =     0
    tcpInWinProbe       =   456    tcpInWinUpdate      =     0
    tcpInClosed         =    99    tcpRttNoUpdate      =  6862
    tcpRttUpdate        =435097    tcpTimRetrans       = 15065
    tcpTimRetransDrop   =    67    tcpTimKeepalive     =   763
    tcpTimKeepaliveProbe=     1    tcpTimKeepaliveDrop =     0

IP
    ipForwarding        =     2    ipDefaultTTL        =   255
    ipInReceives        =11757234  ipInHdrErrors       =     0
    ipInAddrErrors      =     0    ipInCksumErrs       =     0
    ipForwDatagrams     =     0    ipForwProhibits     =     0
    ipInUnknownProtos   =     0    ipInDiscards        =     0
    ipInDelivers        =4784901   ipOutRequests       =4195180
    ipOutDiscards       =     0    ipOutNoRoutes       =     0
    ipReasmTimeout      =    60    ipReasmReqds        =  8723
    ipReasmOKs          =  7565    ipReasmFails        =  1158
    ipReasmDuplicates   =     7    ipReasmPartDups     =     0
    ipFragOKs           = 19938    ipFragFails         =     0
    ipFragCreates       =116953    ipRoutingDiscards   =     0
    tcpInErrs           =     0    udpNoPorts          =6426577
    udpInCksumErrs      =     0    udpInOverflows      =   473
    rawipInOverflows    =     0

ICMP
    icmpInMsgs          =490338    icmpInErrors        =     0
    icmpInCksumErrs     =     0    icmpInUnknowns      =     0
    icmpInDestUnreachs  =   618    icmpInTimeExcds     =   314
    icmpInParmProbs     =     0    icmpInSrcQuenchs    =     0
    icmpInRedirects     =   313    icmpInBadRedirects  =     5
    icmpInEchos         =   477    icmpInEchoReps      =    20
    icmpInTimestamps    =     0    icmpInTimestampReps =     0
    icmpInAddrMasks     =     0    icmpInAddrMaskReps  =     0
    icmpInFragNeeded    =     0    icmpOutMsgs         =   827
    icmpOutDrops        =   103    icmpOutErrors       =     0
    icmpOutDestUnreachs =    94    icmpOutTimeExcds    =   256
    icmpOutParmProbs    =     0    icmpOutSrcQuenchs   =     0
    icmpOutRedirects    =     0    icmpOutEchos        =     0
    icmpOutEchoReps     =   477    icmpOutTimestamps   =     0
    icmpOutTimestampReps=     0    icmpOutAddrMasks    =     0
    icmpOutAddrMaskReps =     0    icmpOutFragNeeded   =     0
    icmpInOverflows     =     0

IGMP:
        0 messages received
        0 messages received with too few bytes
        0 messages received with bad checksum
        0 membership queries received
        0 membership queries received with invalid field(s)
        0 membership reports received
        0 membership reports received with invalid field(s)
        0 membership reports received for groups to which we belong
        0 membership reports sent

The following example shows output from the netstat -r command, which displays the IP routing table.

Routing Table:
  Destination        Gateway           Flags  Ref   Use    Interface
------------------ -------------------- ----- ----- ------ ---------
localhost            localhost             UH       0   2817  lo0
earth-bb             pluto                 U        3  14293  eri0
224.0.0.0            pluto                 U        3      0  eri0
default              mars-gate             UG       0  14142

The fields in the netstat -r report are described in Table 30–2.

Table 30–2 Output From the netstat -r Command


Field Name		Description
`Flags`	`U` `G` `H` `D`	The route is up. The route is through a gateway. The route is to a host. The route was dynamically created by using a redirect.
`Ref`		Shows the current number of routes that share the same link layer.
`Use`		Indicates the number of packets that were sent out.
`Interface`		Lists the network interface that is used for the route.