Changing the netmask

[SteveB42]

OS = AIX 4.1.5
Platform = R50 (PowerPC) Server
2 10Base2 and 1 10/100BaseT NIC (recently installed)

Needed to change Netmask from 255.255.255.0 to 255.255.0.0

Via SMIT was able to change it (returned 'OK'), but when checking it again, it reverts back to 255.255.255.0

Do not have this problem on other machines with similar configurations with one exception, this is my only 4.1.5 machine (cannot upgrade because of development/software) issues.

I removed the device and reinstalled it (including driver) and it still refuses to let me change the netmask! Is there anywhere else I can change it, or another method that may work (already tried chdev -l)?

Any suggestions will be greatly appreciated!!!

Thanks,

 

[Morsing]

aahhh.... Now I understand the probelm. Why didn't you say that right away ;-)

Cheers Henrik Morsing
Certified AIX 4.3 Systems Administration
& p690 Technical Support

 

[sectorseveng]

crbid - can you confirm that this is hardcoded into AIX? My recollection (which could be faulty) was that this problem only occurs when you use the smit screens to make networking changes.

Steve - can you confirm that when you made the ODM changes it appeared to work and it was only when you tried to change the gateway via smit that it reverted to a class C subnet mask?

My recollection was that you could get this to work if you stopped using smitty tcpip and its subscreens and just did the whole tcpip setup via ifconfig as Mr Morsing suggests (and sticking the ifconfig statements into /etc/rc.net to survive reboots), or by just hacking the customised attributes in the ODM.

 

[SteveB42]

Sector,

Already attempted hardcoding the rc.net this morning and it still didn't work. What is very strange about all of this is that all of our other boxes that either run 4.3.3 or 3.2.5 do not exhibit this behavior! The other boxes also use class C ip addresses mixed with class B ... so I just don't get it. #$^@$%^@%$^!@$%!!!!

:-D

 

[SteveB42]

Is there a bug in 4.1.5 or is there a place to set the environment variable concerning what class of network your machine is on? Or could this be particular to the IBM R50 (powerPC) platform?

Thanks again!!!

:-D

 

[sectorseveng]

Steve,

My recollection was that this was specific to 4.1.5. There is no environment variable that can be set to override this behaviour. If ifconfig is not allowing you to use a higher netmask tthen the only thing I can thing of is changing the netmask in the ODM and letting cfgmgr create the interface.

Did changing the netmask in the ODM work?

Note, if you don't want to reboot you should be able to:
1) Make ODM changes.

2) Drop the running interface and the existing config for that interface:
ifconfig en1 down
ifconfig en1 detach
rmdev -l en1

3) Reacquire the interface:
cfgmgr -l en1