Telnet Login Prompt Delays

[Mike Snyder]

I have been having an issue with users trying to telnet into our HP-UX machine. It has to do with users initiating a connection to the box and having them wait for up to 2 minutes for a login prompt.

From what I understand of telnet, after the request is initiated the HP box arp's for the mac. If the IP address of the machine that is trying to telnet into the HP box is in the host table the login prompt comes back immediately.

Well, we have decided to move from a static ip to a dhcp environment. We are also switching to a new ip address structure. Because of this, any PC's on a separate network have a login prompt delay. Is there a way to get around the arp to reduce the delay for the login prompt?

[Rita C Workman]

I'm having a similar problem and found this today....hope it helps both of us.

Telnets from the PCs take about 100 seconds to get a login prompt
because the K-box attempts to resolve the name of the incoming PC.
The K-box doesn't resolve it because it is not in the hosts file.
The K-box then it passes it to the DNS server, which it doesn't have
it registered either. The DNS server finally sends the usuccessful
result back to the K-box which then will give the PC a login prompt.

The way to fix this problem is to make entries in the named.boot file
on the DNS server for each leased IP that the dhcp box serves out.

Note: Restart named.

It doesn't matter what name he gives for the alias of the IP, it
can be pc1 through pc100, if there were that many boxes. Next time
the pc telnets, the DNS box will have a successful lookup and the
login prompt will appear much faster.

[Mike Snyder]

This is great, but I would like to be able to add whole networks at a time. I have about 700 hosts that will be accessing the HP machine, on 7 different networks. Can this still be done?

[Rita C Workman]

Here's the url for the info I found...there is no mention of a 'limit of entries'. So I say give it a go.....

http://us-support2.external.hp.com/cki/bin/doc.pl/sid=72807a9e08ee085bd6/screen=ckiDisplayDocument?docId=200000027709160

I'm starting on mine tomorrow....let me know how it goes..


Regards,

[Tim Malnati]

Another thing to keep in mind. When you login to a machine, quota checking is performed on all mounted file systems, including NFS mounts. It is particularly noticible if you have NFS mounts that have a somewhat high latency delay (from a wan or similar).

[James R. Ferguson]

Mike:

My experience suggests that the delay you are seeing is due to "reverse-name-lookup". Making sure that your device's name is represented in the DNS tables of the DNS server will eliminate the (timeout) delay. [I know that this is not what you wanted to here!].

Reverse lookup is the process by which a server receiving a request for service from a remote machine ascertains whether the identity claimed by the machine is in fact its true one. The process goes like this:

1. The request arrives in a packet with an IP address indicating the point of origin.
2. The server queries name service on the net to find out what host name is associated with that IP address.
3. The server then queries name service to find out what IP address is associated with that host-name.
4. If this last request fails to find an IP address, or finds one that doesn't match the original, the request for service is rejected.

For an good description of reverse name lookup, see:

http://www.helpdesk.umd.edu/comm/ethernet/revlook.shtml

...JRF...

[Keith Floyd]

Hi

Has a similar problem.

modified /etc/nsswitch.conf and left hosts: as files - I did not need reverse DNS lookup

worked a treat.

Keith

[Berlene Herren]

Mike, is ypbind running, and you are not using NIS? I have seen this cause this exact problem.

Berlene