Network Adapter Issue in AIX

Network Issue Troubleshooting

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 127 127.0.0.1 587 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. 216.131.202.172 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 216.131.202.172 Internet address TRUE
state up Current Interface Status TRUE
netmask 255.255.255.0 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 216.131.202.10 UG 1 397 en0 - -
127/8 127.0.0.1 U 4 265 lo0 - -
216.131.202/24 216.131.202.172 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
? (216.131.202.191) at 8:0:20:92:a1:c6 (ethernet)
? (216.131.202.171) at 0:10:83:27:ba:7f (ethernet)

6. Check transmit and receive stats:

# enstat -d ent0 | more
----------------------------------------------------------
ETHERNET STATISTICS (ent0) :
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 ple-dns-01.peoplesoft.com.domain > st-ibm07.peoplesoft.com

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