Delay After Connection To Linux Server

Andrew Kaplan
Super Advisor

Delay After Connection To Linux Server

Hi there,

I have a server running Red Hat Linux 7.3 with two ethernet interfaces. Each interface is connected to a separate network. The network on the first interface is an exclusive network to a small group of servers and has its own ip address and domain name. The second interface is connected to the company's network and has a company ip address and domain name. The problem that I am encountering is the following: After establishing a telnet connection to either one of the interfaces, there is about a one minute delay before a a login prompt is displayed on the screen. After it appears I am able to log into the system succesfully. The /etc/hosts file has the ip addresses and the respective domain names for each of the interfaces. The /etc/resolve.conf file has the ip address of the DNS servers the company uses and the hostname and ip address of the server in question has been added to the DNS server of the company. Is there a setting that needs to be modified to correct this problem?
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Stuart Browne
Honored Contributor

Re: Delay After Connection To Linux Server

Once on the linux box, do a simple 'nslookup' of the host IP address you're telnetting *FROM* (not too).

It really does sound like there's an issue with the reverse lookup that gets performed when you telnet to the machine.

In older versions of the tcp wrappers, this was a configuruable flag in the /etc/hsots.{allow,deny} files (PARANOID lookup, tries to match forward/reverse lookups). By default, the RH tcp wrappers do a minimum of look the address up.

It's possible that whilst there's forward DNS lookup, there's no reverse for your IP range, thus causing the delay.

If this isn't it, then you'd best start looking at firewalls, and routing tables.
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