[c-nsp] Cisco ASA 5520 and DHCP relay

Alasdair Gow alasdair.gow at lumison.net
Wed Mar 12 12:13:04 EDT 2008


Have you tried taking the asa out of the equation?

Use a switch (or crossover depending on your setup) and once you know 
the linux box is doing dhcp correctly put the asa back in.

Or have you done this already?

What are the logs on the asa saying?

Whats the MTU set at, everything the same? win/asa/linux?

Can you run tcpdump on the linux client and then set to dhcp and see if 
its sending ok?

Ally


Eimantas Zdanevičius wrote:
> Hello all,
>
>
> I have linux dhcp server connected to one ASA 5520 (routing mode, single 
> context) interface, and dhcp clients connected to other ASA 5520 
> interface. I have set dhcprelay agent on asa:
>
> dhcprelay server dhcp_server servers
> dhcprelay enable test
> dhcprelay timeout 60
>
> 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;
> authoritative;
> subnet 10.5.0.0 netmask 255.255.255.0 {
>         option routers                  10.5.0.254;
>         option subnet-mask              255.255.255.0;
>         option domain-name-servers      10.0.0.1,10.0.0.2;
>         host asus { fixed-address 10.5.0.20; hardware ethernet 
> 00:18:f3:3e:bc:3e; }
> }
>
> I have laptop (named asus in dhcp config) with Windows XP and Linux 
> operating systems. When i run Windows XP my laptop gets ip address and 
> all works fine. But linux cant get ip address from dhcp server.
>
> i can't see any activity on dhcp server from linux client (message.log, 
> tcpdump), when i run windows i see DHCP messages on dhcp server.
>
>
> how can i resolve this problem?
>
> How can i debug dhcp packets on asa5520?
>
>
> Thanks,
> Eimantas
>
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Alasdair Gow
Lumison
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