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Double DHCP Pools on Router

trapneto
Level 1
Level 1

#show startup-config on our Cisco 897VA produces this:

ip dhcp pool school-dhcp-pool
import all
network 10.10.10.0 255.255.255.0
default-router 10.10.10.1
dns-server 208.67.220.220 208.67.222.222
lease infinite
!
ip dhcp pool talkswitch
host 10.10.10.199 255.255.255.0
hardware-address 000f.4d00.a463
!

(1) Does this mean that EVERY IP is available to school-dhcp-pool, even 10.10.10.1, which is the router itself?

(2) How does the talkswitch pool interact with the school-dhcp-pool?

(3) Is there a way to list DHCP reservations, if any?

4 Replies 4

ammahend
VIP
VIP

(1) Does this mean that EVERY IP is available to school-dhcp-pool, even 10.10.10.1, which is the router itself?

yes, you should configure exclusion 

ip dhcp exclude-address <address range>

(2) How does the talkswitch pool interact with the school-dhcp-pool?
You have to configure exclusion for 10.10.10.199, that address is reserved for max address listed in config. 

(3) Is there a way to list DHCP reservations, if any?

talkswitch is an example of reservation. 

-hope this helps-

I have a server with a DHCP assignment of 10.10.10.17 with an "infinite" lease.  I've just discovered that DHCP can change an "infinite" lease automatically if the device is moved from one network location to another on the same network.  I can't log into the server, because the admin credentials have been lost, and I don't have time right now to factory reset it.  So I can't assign an IP manually.

If I use 

   ip dhcp exclude-address 10.10.10.17

will the server still have IP 10.10.10.17, or will DHCP immediately assign a different, non-reserved IP to the server?

Hello,

(1) Does this mean that EVERY IP is available to school-dhcp-pool, even 10.10.10.1, which is the router itself?

--> No. The default router address (10.10.10.1 in your case) and the manually bound address (10.10.10.199) will not be dished out by the DHCP server, they are automatically excluded, you do not need to configure 'ip dhcp excluded-address' statements for these addresses.

(2) How does the talkswitch pool interact with the school-dhcp-pool?

--> There is no 'interaction' other than that the manually bound IP addresses are excluded automatically from the dynamic pool.

(3) Is there a way to list DHCP reservations, if any?

--> show ip dhcp binding (that is the closest command I can think of)

ip dhcp pool school-dhcp-pool
import all
network 10.10.10.0 255.255.255.0
default-router 10.10.10.1
dns-server 208.67.220.220 208.67.222.222
lease infinite
!
ip dhcp pool talkswitch
host 10.10.10.199 255.255.255.0
hardware-address 000f.4d00.a463

First the talkswitch host IP is automatic exclude from the school-dhcp pool 

second router IP you can config exclude it or you can not the different that 
if you not exclude it then router may assig to client BUT here the client send ARP to check if this IP is used or not and router will reply and hence the client refuse the IP, 
so it simple ask the router to not use this IP (exclude it)

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