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2 DS20E servers on same network.

 
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robert70
Valued Contributor

2 DS20E servers on same network.

i am running a DS20E with VMS 7.3-2 and Pathworks.We connect using telnet.
I have a configured a 2nd DS20E box with same operating system/pathworks with different node name and IP address. When this 2nd server is placed on the network it crashes some of the original servers telnet sessions and the new servers telent sessions dont appear to work? should the subnet mask and/or broadcast IP be the same in both machines?
any help please!
14 REPLIES 14
Duncan Morris
Honored Contributor

Re: 2 DS20E servers on same network.

Robert,

Welcome to the itrc OpenVMS forum.

please give us some more details to work with.

Can you show your IP configuration on both systems with $TCPIP SHOW INTER.

Can you give the versions of PATHWORKS and TCPIP (and which vendor!)?

Regards to Auld Reekie,

Duncan


Andy Bustamante
Honored Contributor

Re: 2 DS20E servers on same network.


>>> I have a configured a 2nd DS20E box with same operating system/pathworks with different node name and IP address.

Did you do a fresh operating system installation or did you use a copy of the existing system? If you're using a copy of the first DS20e, you'll also need to update the DECnet address. DECnet sets the MAC address based on the address which may cause some interesting network behavior. See the VMS FAQ at Hoffmanlabs.com. http://64.223.189.234/node/589

Of course you've also made sure to update the license database with the appropriate products for your new system if this is a copy.

Andy
If you don't have time to do it right, when will you have time to do it over? Reach me at first_name + "." + last_name at sysmanager net
Hoff
Honored Contributor

Re: 2 DS20E servers on same network.

If telnet sessions are tipping over, there's probably an address collision, or a routing error of some sort, that's been introduced here. There are some somewhat less likely triggers potentially lurking here, such as a screaming (failed) network controller, or a cable fault or such. And it's easy to miss an address collision on a secondary controller, too.

As for whether subnet mask and the broadcast address are the same, all nodes within a particular subnet typically share those values. The hosts will typically also share a default route and some other values.

If there's a VLAN and addresses are messed up, all bets are off; all sorts of weirdness can arise as the VLANs try to deal with the address collision.

That this subnet question is being asked could indicate some unfamiliarity with IP networking. For one form of that and as applied to OpenVMS, please see the introductory manual in the TCP/IP Services documentation.

If the second AlphaServer DS20e system disk was cloned from the first, then you may want to read this discussion on the various spots where the node name and node address can lurk: http://64.223.189.234/node/589
robert70
Valued Contributor

Re: 2 DS20E servers on same network.

Duncan,

Thanks, hope you can help
auld reekie is cold today!

Existing machine
IE0
129.94.185.45 255.255.255.128 LO0
127.0.0.1 255.0.0.0

New Machine
IE0
129.94.185.46 255.255.255.128 LO0
127.0.0.1 255.0.0.0


Robert

robert70
Valued Contributor

Re: 2 DS20E servers on same network.

>>Did you do a fresh operating system installation or did you use a copy of the existing system? If you're using a copy of the first DS20e, you'll also need to update the DECnet address. DECnet sets the MAC address based on the address which may cause some interesting network behavior. See the VMS FAQ at Hoffmanlabs.com. http://64.223.189.234/node/589

Hoff, yes i used a copy of the existing system. do i still need to update the decnet address even if im using pathworks? not using decnet at all?
robert70
Valued Contributor

Re: 2 DS20E servers on same network.

sorry last reply meant for andy apologies
Robert Gezelter
Honored Contributor

Re: 2 DS20E servers on same network.

Robert,

As noted, having the same DECnet addresses can play havoc, particularly since the MAC address of a DECnet node is reset to a formula that includes the DECnet node number.

If this is the case, I would suspect that the ARP tables are getting confused. Suggestion, verify the contents of the ARP tables on the last hop router.

If my suspicion is correct, the SCSID and DECnet node address need to be changed in concert (at the same time).

Please remember to change the SCSID in the files used by AUTOGEN to prevent a future recurrence.

- Bob Gezelter, http://www.rlgsc.com
robert70
Valued Contributor

Re: 2 DS20E servers on same network.

>>Suggestion, verify the contents of the ARP tables on the last hop router.

If my suspicion is correct, the SCSID and DECnet node address need to be changed in concert (at the same time).

Please remember to change the SCSID in the files used by AUTOGEN to prevent a future recurrence.

Thanks Bob
Im pretty new to all this - how do you verify contents of arp table and how do you change the decnet node address?
thanks
robert
Duncan Morris
Honored Contributor

Re: 2 DS20E servers on same network.

Robert,

you should just be able to change SCSSYSTEMID in sys$system:modparams.dat, and rerun sys$update:autogen.com to set a new value, as you said that you are not using DECnet at all. Is it even installed?

$type sys$system:modparams.dat
!
SCSNODE="DEVT02"
SCSSYSTEMID=1175
.
.

Read the notes that Andy and Hoff referenced earlier - they are quite important!

Duncan
robert70
Valued Contributor

Re: 2 DS20E servers on same network.

>>Robert,

you should just be able to change SCSSYSTEMID in sys$system:modparams.dat, and rerun sys$update:autogen.com to set a new value, as you said that you are not using DECnet at all. Is it even installed?

$type sys$system:modparams.dat
!
SCSNODE="DEVT02"
SCSSYSTEMID=1175

thanks duncan
does it matter what the scssystemid is set to? it is currently the same as the original machine eg 65534
Duncan Morris
Honored Contributor

Re: 2 DS20E servers on same network.

Robert,

the SCSSSYTEMID was constructed from a DECnet address orginally.

Address a.b gave an ID of

(1024 * a) + b

So your first node has a (theoretical) address of 63.1022 (area 63, node 1022)

If you make your other node 65533 then that would equate to 63.1021

On my sample, 1175 gives 1.151

Duncan
robert70
Valued Contributor

Re: 2 DS20E servers on same network.

thanks duncan ill try that change
rerun autogen and reboot
Robert Gezelter
Honored Contributor
Solution

Re: 2 DS20E servers on same network.

Robert,

My general recommendation is to set the SCSSYSTEMID to a value which is a reasonable DECnet address.

There are many situations in which it is particularly handy to have DECnet connectivity between OpenVMS systems in a multimachine environment. Setting the address to a reasonable value makes it that much easier to enable DECnet without requiring changes and reboots.

- Bob Gezelter, http://www.rlgsc.com
robert70
Valued Contributor

Re: 2 DS20E servers on same network.

thanks to everyone for their help on this thread
my 1st time ive used this forum and very impressed
many thanks
all seems to be working correctly now - the scssystemid was the problem
cheers
Robert