topic ASA dhcpd address restriction in Network Security

ASA dhcpd address restriction

p.sarabande — Tue, 12 Mar 2019 01:47:58 GMT

Hello.

I have a question on ASA dhcpd address restriction.

I've noticed that maximum available DHCP pool is restricted to 256 addresses.
http://www.cisco.com/en/US/docs/security/asa/asa84/configuration/guide/basic_dhcp.html#wp1125257

Is it merely the restriction for dhcp pool per interface or restriction per device?

For example, let's say I have 5 interface with dhcpd enabled and have set the pool address as follows:

dhcpd address 192.168.10.10-192.168.10.254 segment10
dhcpd address 192.168.11.10-192.168.11.254 segment11
dhcpd address 192.168.12.10-192.168.12.254 segment12
dhcpd address 192.168.13.10-192.168.13.254 segment13
dhcpd address 192.168.14.10-192.168.14.254 segment14

Which below is true?
1. If 100 addresses are provided from segment10 and segment11, only 56 addresses are left available for rest of the segment.
2. It's possible to provide 245 addresses per segment as configured. (device can provide 245*5 addresses to client.)

Thanks in advance!

Regards,

Saki

ASA dhcpd address restriction

Jouni Forss — Thu, 23 May 2013 10:47:05 GMT

Hi,

The maximum size of a single DHCP Pool is 256 IP addresses. To be able to use so large pool would require your ASA interface where the DHCP is enabled to be larger than /24. With /24 mask network you can assing 253 IP address pools.

To my understanding each interface can only have one DHCP Pool and each Pool can be of the maximum size

The ASA is not that flexible as a DHCP server so usually its better to use some IOS router/L3 switch or an actual DHCP server.

Hope this helps

Remember to mark the reply as the correct answer if it answered your question or ask more if needed

- Jouni

ASA dhcpd address restriction

p.sarabande — Fri, 24 May 2013 00:57:58 GMT

Thanks Jouni,

But my question is about the amount of DHCP pool that can be used for device that has multiple interfaces.

interface gig0/0.10
vlan 10

nameif segment10
ip address 192.168.10.1 255.255.255.0
security 100

interface gig0/0.11

nameif segment11

ip address 192.168.11.1 255.255.255.0

security 100

.... and so on.

Is there any clue?

Regards,
Saki

ASA dhcpd address restriction

Jouni Forss — Fri, 24 May 2013 03:19:45 GMT

Hi,

As I said, I think the ASA can have 1 maximum size DHCP Pool per interface. The amount of interface shouldnt really matter.

Quote from the Configuration Guide of ASA

You can configure only one DHCP server on each interface of the ASA. Each interface can have its

own pool of addresses to use.

So basicly each interface can have a pool.

Hope this helps

Remember to mark the reply as correct answer if it answered your question.

- Jouni