Cisco ASA 5520 and DHCP relay

Glenn Satchell Glenn.Satchell at
Fri Mar 14 12:06:26 UTC 2008

>Date: Fri, 14 Mar 2008 13:48:27 +0200
>From: Eimantas Zdanevičius <eimantas at>
>To: dhcp-users at
>Subject: Re: Cisco ASA 5520 and DHCP relay
>> On the client what is in /etc/resolv.conf? Is it getting created
>> by the dhcp client? What dhcp client are you using? dhclient, or
>> something else?
>I'm using dhclient. /etc/resolv.conf created by dhclient and contains 
>only nameserver lines:
>these dns servers works correctly for other clients
>> What setings do you have in dhcpd.conf for domain name servers?
>Linux DHCP server configuration:
>default-lease-time  1800;    # 1/2 hour
>max-lease-time      3600;    # 1 hour
>min-lease-time       900;    # 1/4 hour
>one-lease-per-client true;
>option arp-cache-timeout 3600;
>option netbios-node-type 1;
>ddns-update-style none;
>ddns-updates off;
>subnet netmask {
>       option routers        ;
>       option subnet-mask    ;
>       option domain-name-servers,;
>       host asus { fixed-address; hardware ethernet
>00:18:f3:3e:bc:3e; }
>> If neither of these is helpful, then using tcpdump or wireshark
>> to look at the packets on the network may give some clues.
>For now i can't test with tcpdumpor wireshark , i wil do this later.
add a line to dhcpd.conf on the server

    option domain-name "";

to set the default domain, not sure if that will help, but it should
ensure the domainname entry goes in /etc/resolv.conf.

What is in /etc/resolv.conf on the clients that do work?


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