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network

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December 15, 2011 11:30 am

Executing the command /usr/sbin/automount hangs

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by    in AIX

Question

Why does /usr/sbin/automount hang?

Answer

1) Verify that /etc/netsvc.conf contains the following line:

hosts=local,bind4

Verify that /etc/hosts contains the following:

127.0.0.1 loopback localhost

Verify that the ip address and the hostname of the machine is defined in /etc/hosts

Verify that loopback and the hostname of the machine can be resolved.

# host loopback

# host 127.0.0.1

# host machine’s_hostname

# host machine’s_ip_address

 

2) Verify that the loopback interface lo0 exist and doesn’t have an * next to the interface name.

There should be 3 lines of output for lo0. There shouldn’t be an * next to lo0.

# netstat -in
lo0 16896 link#1 27658535 0 27663128 0 0
lo0 16896 127 127.0.0.1 27658535 0 27663128 0 0
lo0 16896 ::1 27658535 0 27663128 0 0

If there is an * next to lo0 this indicates that lo0 is in a down state.

Check the state of lo0 in the ODM. The state should be up.

# lsattr -El lo0

<….>
state up Current Interface Status

<….>

If the state is up in the ODM use the following command to make lo0 available
# mkdev -l lo0
Available

If the state is down or detach in the ODM use the following commands to bring lo0 up
# chdev -l lo0 -a state=up -P
# mkdev -l lo0

 

NOTE: If lo0 is missing from the netstat -in output run cfgmgr to bring back lo0.

Check the ODM and the netstat -in output using the above commands and take the appropriate actions.

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November 18, 2010 4:37 pm

How to disable IPV6 on AIX 5.3 and 6.1

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1. Delete the localhost IPv6 from lo0

root [AIX Servers] /: lsattr -El lo0
mtu           16896     Maximum IP Packet Size for This Device     True
netaddr       127.0.0.1 Internet Address                           True
netaddr6      ::1       IPv6 Internet Address                      True
netmask                 Subnet Mask                                True
prefixlen               IPv6 Alias including Prefix Length         True
rfc1323                 Enable/Disable TCP RFC 1323 Window Scaling True
state         up        Current Interface Status                   True
tcp_mssdflt             Set TCP Maximum Segment Size               True
tcp_nodelay             Enable/Disable TCP_NODELAY Option          True
tcp_recvspace           Set Socket Buffer Space for Receiving      True
tcp_sendspace           Set Socket Buffer Space for Sending        True
root [AIX Servers] /: chdev -l lo0 -a netaddr6=''
lo0 changed
root [AIX Servers] /: lsattr -El lo0
mtu           16896     Maximum IP Packet Size for This Device     True
netaddr       127.0.0.1 Internet Address                           True
netaddr6                IPv6 Internet Address                      True
netmask                 Subnet Mask                                True
prefixlen               IPv6 Alias including Prefix Length         True
rfc1323                 Enable/Disable TCP RFC 1323 Window Scaling True
state         up        Current Interface Status                   True
tcp_mssdflt             Set TCP Maximum Segment Size               True
tcp_nodelay             Enable/Disable TCP_NODELAY Option          True
tcp_recvspace           Set Socket Buffer Space for Receiving      True
tcp_sendspace           Set Socket Buffer Space for Sending        True
root [AIX Servers] /:
root [AIX Servers] /: ifconfig -a
en0: flags=5e080863,c0<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),PSEG,LARGESEND,CHAIN>
 inet 59.30.4.9 netmask 0xffffff00 broadcast 59.30.4.255
 tcp_sendspace 131072 tcp_recvspace 65536 rfc1323 0
lo0: flags=e08084b<UP,BROADCAST,LOOPBACK,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT>
 inet 127.0.0.1 netmask 0xff000000 broadcast 127.255.255.255
 inet6 ::1/0
 tcp_sendspace 131072 tcp_recvspace 131072 rfc1323 1
root [AIX Servers] /: ifconfig lo0 inet6 ::1/0 delete
root [AIX Servers] /: ifconfig -a
en0: flags=5e080863,c0<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT,CHECKSUM_OFFLOAD(ACTIVE),PSEG,LARGESEND,CHAIN>
 inet 59.30.4.9 netmask 0xffffff00 broadcast 59.30.4.255
 tcp_sendspace 131072 tcp_recvspace 65536 rfc1323 0
lo0: flags=e08084b<UP,BROADCAST,LOOPBACK,RUNNING,SIMPLEX,MULTICAST,GROUPRT,64BIT>
 inet 127.0.0.1 netmask 0xff000000 broadcast 127.255.255.255
 tcp_sendspace 131072 tcp_recvspace 131072 rfc1323 1
root [AIX Servers] /:

2. Remove IPv6 from net services file /etc/netsvc.conf.

Edit /etc/netsvc.conf
The default, on AIX, is thus:
hosts=local,bind
Replace this with:
hosts = local4,bind4
to deactivate searching for IPv6 addresses.
No newline at end of file
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September 17, 2010 11:32 pm

Verify and test that a UDP port is open

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by    in AIX

Technote (FAQ)


This document applies only to the following language version(s):

US English

Question

How to verify that a UDP port is open and how to test that the port is working for a third party application.

Answer

Command to verify that a port is open to receive incoming connections.

#netstat -an |grep <port number>

Example: tftp uses port 69 to transfer data

#netstat -an |grep .69

Proto Recv-Q Send-Q Local Address Foreign Address (state)
udp 0 0 *.69 *.*


To capture the udp packets to prove that a specific port is being used you can either run the tcpdump command or the iptrace command.

#tcpdump "port #" (where # is the number of the port you are testing)

or
#startsrc -s iptrace -a "-a -p # /tmp/udp.port" (where # is the number of the port you are testing)
#stopsrc -s iptrace (stop iptrace command)
#ipreport -rnsC /tmp/udp.port /tmp/udp.port.out (format the iptrace binary to a text readable format)

Example: Start the packet capture.

#tcpdump 'port 69'

Then use tftp to transfer a file. This is an example of transferring the /etc/motd file from a system called dipperbso to a system called burritobso.

#tftp -p /etc/motd burritobso /tmp/motd 

Example of the output:

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on en0, link-type 1, capture size 96 bytes
08:50:24.627840 IP dipperbso.52046 > burritobso.tftp: 21 WRQ "/tmp/motd" netascii

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