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ASA and DHCP server

Hi Everyone,

ASA is configured as DHCP to allow IP to users.

When i  sh dhcpd binding it shows all the IP assigned by the ASA.

Once i reboot the ASA and do

sh dhcpd binding

it does not show any IP assigned previously even though i can ping those IP.

IS this default behaviour?

Regards

Mahesh

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

ASA and DHCP server

Mahesh

Yes this is default behavior. Perhaps it might help to think about it in this way:

- The ASA creates entries in the binding table as it assigns an IP address to a host.

- The binding table is maintained in memory of the ASA.

- Once a host has been assigned an IP address it keeps that address for the duration of the lease.

- When the ASA boots the contents of memory, including the binding table, are erased and start over.

So after the ASA boots the binding table starts empty and the hosts on the network have their IP address. So you can ping the hosts even there is not an entry in the binding table. Note that what allows you to ping the host is whether there is an entry in the ARP table and not whether there is a binding entry for the host.

HTH

Rick

2 REPLIES
Hall of Fame Super Silver

ASA and DHCP server

Mahesh

Yes this is default behavior. Perhaps it might help to think about it in this way:

- The ASA creates entries in the binding table as it assigns an IP address to a host.

- The binding table is maintained in memory of the ASA.

- Once a host has been assigned an IP address it keeps that address for the duration of the lease.

- When the ASA boots the contents of memory, including the binding table, are erased and start over.

So after the ASA boots the binding table starts empty and the hosts on the network have their IP address. So you can ping the hosts even there is not an entry in the binding table. Note that what allows you to ping the host is whether there is an entry in the ARP table and not whether there is a binding entry for the host.

HTH

Rick

New Member

Re: ASA and DHCP server

Many thanks Rick for explaining so well.

I can see the entries in the ARP table.

I though earlier that ASA DHCP might works differently then Routers and switches.

Best Regards

Mahesh

Message was edited by: mahesh parmar

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