telnet connections take too long

[MANOJ JAIN_2]

Recently we have been experiencing a delay while connecting to one of our HP-UX (K Series, 11.0) servers. At times we have to wait for over a minute to get a login prompt.

Does anyone know, why this is happeneing?

[Antoanetta Naghiu]

Are you using /etc/hosts or DNS or NIS for resolving name?
Run nslookup to see. If DNS, ensure both nodes are there, check /etc/resolv.conf and check as well the routes. If using /etc/hosts edit in both nodes to be sure both machine entries (ip's and names are there).
Check /etc/nsswitch.conf.
Any better?

[RikTytgat]

Hi,

Antoanetta is right. The reason this happens is because of something called 'reverse lookup' to verify the source of the connection.

What the telnet server does is:
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.

This method is used as a measure against IP spoofing.

See http://www.helpdesk.umd.edu/comm/ethernet/revlook.shtml for a complete description of reverse lookup.

Bye,
Rik

[RikTytgat]

Hi,

Antoanetta is right. The reason this happens is because of something called 'reverse lookup' to verify the source of the connection.

What the telnet server does is:
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.

This method is used as a measure against IP spoofing.

See http://www.helpdesk.umd.edu/comm/ethernet/revlook.shtml for a complete description of reverse lookup.

Bye,
Rik

[John Palmer]

This is almost certainly caused by the server defined as the primary DNS server being unavailable.

Check /etc/resolv.conf for the IP address of the DNS server.

The 60 second delay is the timeout period for the DNS lookup.

You will also notice the delay when doing any other DNS lookups. Compare netstat -a (which attempts to resolve the connected IP addresses) and netstat -an which doesn't.

[James R. Ferguson]

Hi:

My experience too, suggests that the delay you are seeing is due to "reverse-name-lookup". Make sure that your device's name is represented in the DNS tables of the DNS server and the delay should disappear.

...JRF...

[Jeremiah Campbell]

You might also check which telnet patch is currently installed. PHNE_16546 fixed a problem with "telnet connection hanging" on 11.0.

I would suggest patching up to PHNE_19298 if you are conservative, or go with the latest (Not Yet HP Recommended) PHNE_21822 if you like to take chances. Stay away from PHNE_20936 which was recalled.

[M.J. van der Meer]

Hi,

Possible cause can also be that a router in your network is working on half duplex and your server on full, or the other way around.
Did you check that?

Regards
MJ

[Art Evans]

Insure when checking the duplex settings, on the server you use lanadmin.
Sam, sometime has problems reporting the right duplex.