Trouble Shooting AIX Networking


TroubleShooting AIX


System Reporting wrong oslevel:




1. Check the number of network interfaces and their status:
# lsdev -CH | grep en
ent0 available 10-68 3Com 3C905-TX-IBM fast Etherlink XL NIC
ent1 defined 10-80 IBM PCI Ethernet Adapter (22100020)
inet0 available Internet Network Extension
en0 available Standard Ethernet Network Interface
en1 defined Standard Ethernet Network Interface


In this example, there are two network interfaces, ent0 and ent1. ent0 is a fast, 100MB card while ent1 is a 10MB card. ent0's status is "available" meaning that is presently active; on the other hand, ent1's status is "defined" which means that it could be activated but is not at this time.


2. Use the netstat command:
# netstat -in
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
lo0 16896 link#1          587    0     695    0     0
lo0 16896 127   587    0    695     0     0
lo0 16896 ::1             587     0    695    0     0
en0 1500 link#6 2.60.8c.f2.1d.f6 6455 0 1112 0     0
en0 1500 216.131.202. 6455 0 1112 0 0


Check that the first three lines are lo0, also, confirm that en0 is the active interface, record the IP number.


3. Investigate the attributes of the active interface:
   # lsattr -El en0  
     mtu          1500           Max IP Packet Size for this device        TRUE
     remmtu        576           Max IP Packet Size for remote networks    TRUE
     netaddr  Internet address                        TRUE
     state        up            Current Interface Status                   TRUE
     netmask Subnet mask                                TRUE
     security     none          Security level                             TRUE
     authority                  Authorized Users                           TRUE
     broadcast                  Broadcast Address                          TRUE
     netaddr6                   N/A                                        TRUE
     alias6                     N/A                                        TRUE
     prefixlen                  N/A                                        TRUE
     alias4                     N/A                                        TRUE

4.Determine the routing information:
#netstat -rn
     Routing tables
     Destination       Gateway  Flags    Refs  Use    If    PTMU     Exp Groups
     Route tree for Protocol Family 2 (internet) :
     default              UG       1    397    en0 -        -
     127/8                U       4    265    lo0     -        -
     216.131.202/24  U       3  35419   en0      -        -

Check that the router's IP number is the correct one and that the U and G flags are set.

5. Use the arp command to check on address resolution:
# arp -an
     ? ( at 8:0:20:92:a1:c6 (ethernet)
     ? ( at 0:10:83:27:ba:7f (ethernet)

6. Check transmit and receive stats:
   # enstat -d ent0 | more
     Device Type: 3Com 3C905-TX-IBM Fats Etherlink XL
     NIC Harware address: 02:60:8c:f2:1d:f6
     Elapsed Time: 0 days 2 hours 5 minutes 48 seconds

     Transmit Statistics:                        Recieve Statistics:
     --------------------                        -------------------
     Packets: 38269                              Packets: 25841
     Bytes: 45846710                             Bytes: 5512839
     Interrupts: 38269                           Interrupts: 25651
     Transmit Errors: 0                          Receive Errors: 0
     Packets Dropped: 0                          Packets Dropped: 0

   If there are no packets sent or received, there is probably a cable problem.

7. Look at the duplex and speed setting on the card:
   # smit chgenet [choose en0]
     Ethernet Adapter                                 ent0
     Media Type                                       100BaseTX
     TX to RX Queue Partition Ratio                   3:5
     Driver TX Waiting Queue Size                     32
     Driver RX waiting Queue Size                     32
     Full Duplex?                                     yes
     Use alternate address?                           no
     Alternate Ethernet Address                       0x
     TX Start Threshold - Fragmented                  512
     Apply change to DATABASE only                    no

If the card is not set as above, it is recommended that it should. To change the above settings:
    a. Telnet to server's console
    b. Detach the card:
# ifconfig en0 detach
    c. Reconfigure it:
# smit chgenet
    d. Bring it up:
# chdev -l en0 -a state=up
    e. Reset tcpip:
# smit tcpip

8. Try to listen to the port:
# tcpdump -i en0 -I
     18:34:20.333473494   >


If you don't see any output, then probably the cable that connects to the catalyst or the catalyst port itself could be defective.


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