“no ip dhcp excluded-address” not removing entry

[juddcharles]

hello, 

I am a small home office user. Recently moved config from an old Cisco 1900 to a newer Cisco 1100 series.

I am unable to remove a excluded DHCP scope statement.  From the cli "no ip dhcp excluded-address x.x.x.x x.x.x.x" does not remove the entry.  As a result, I only have 25 DHCP addresses to play with, and the next DHCP clients are not being issued DHCP addresses.  Pool is exhausted.

Ios config clearly has a DHCP exclusion scope... I have no idea how it got there but I can't remove it.

How can I remove the excluded-address statement please?

!
ip host CISCO-CAPWAP-CONTROLLER.local 10.0.2.5
ip host cisco-lwapp-controller.local 10.0.2.5
ip name-server 8.8.8.8 8.8.4.4
no ip domain lookup
ip domain name .local
ip dhcp excluded-address 10.0.1.26 10.0.1.255
!

I've tried deleting the DHCP pool, then removing the excluded-address entry, and then re-adding the DHCP pool.  Issuing the command under config t does not remove the entry.  A reboot does not remove the entry.  it's like it's locked or read only or something.

no ip dhcp excluded-address 10.0.1.26 10.0.1.255

DHCP Debug log shows

DHCPD: subnet [10.0.1.1,10.0.1.254] in address pool LAN-pool1 is empty.
DHCPD: due to: POOL EXHAUSTED

Router address is 10.0.1.254

DHCP Pool assigned as 

ip dhcp pool LAN-pool1
import all
network 10.0.1.0 255.255.255.0
default-router 10.0.1.254
dns-server 10.0.1.254
domain-name .local
option 43 ascii "10.0.2.5"
lease 1

DHCP utilisation shows

Pool LAN-pool1 :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 65534
Leased addresses : 0
Excluded addresses : 245
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased/Excluded/Total
10.0.0.1 10.0.0.1 - 10.0.255.254 0 / 245 / 65534

Clients connect via a catalyst switch via VLAN10 with DHCP helper address pointing to router.

interface Vlan10
ip address 10.0.1.97 255.255.255.0
ip helper-address 10.0.1.254
no ip redirects
no ip unreachables
no ip proxy-arp
ip pim sparse-dense-mode
ip igmp join-group 239.20.226.197
ip igmp version 3
ip cgmp

 installed ios version 

System image file is "flash:c1100-universalk9.17.08.01a.SPA.bin"
Cisco IOS XE Software, Version 17.08.01a 

[Georg Pauwen]

Hello,

try and disable the DHCP service first before removing the reservation:

1100(config)#no service dhcp

[juddcharles]

Thanks Georg,

I tried disabling/removing the DHCP service and then removing the excluded address-statement, and it is still not removed.   It is like it's administratively locked or read only.  I get no message on console or log when trying to remove it.

The process I used described below;

Remove DHCP service
C1121X-8PLTEP(config)#no service dhcp

Remove DHCP pool

C1121X-8PLTEP(config)#no ip dhcp pool LAN-pool1

Save config

C1121X-8PLTEP#write mem

Remove exclude-address scope

C1121X-8PLTEP(config)#no ip dhcp excluded-address 10.0.1.26 10.0.1.255

Save config

C1121X-8PLTEP#write mem

show run and the exclude scope is still there

show run
C1121X-8PLTEP#ip dhcp excluded-address 10.0.1.26 10.0.1.255  <<< entry still there

Save and reload the router

C1121X-8PLTEP#copy run start
C1121X-8PLTEP#reload

after reload, the entry is still there

show run
C1121X-8PLTEP#ip dhcp excluded-address 10.0.1.26 10.0.1.255   << entry still there after reload

Try removing the exclude scope again

C1121X-8PLTEP(config)#no ip dhcp excluded-address 10.0.1.26 10.0.1.255

Save config

C1121X-8PLTEP#write mem

show run to see if the exclude scope is still there... and it's still there

show run
C1121X-8PLTEP#ip dhcp excluded-address 10.0.1.26 10.0.1.255

very frustrating.

I also tried viewing, then clearing DHCP conflicts.  there was one record in there.

C1121X-8PLTEP#show ip dhcp conflict
IP address Detection method Detection time VRF
10.0.1.6 Ping Feb 10 2023 09:21 AM

C1121X-8PLTEP#clear ip dhcp conflict *
C1121X-8PLTEP#show ip dhcp conflict
IP address Detection method Detection time VRF

Conflict table is now empty.

[juddcharles · Accepted solution]

I found the problem.

There was this entry in the ios config 

app-hosting appid guestshell
app-vnic management guest-interface 0
guest-ipaddress 10.0.1.254 netmask 255.255.255.0
end

I dont use the "app-hosting" capability on the Cisco 1100 router...and it appears to be bad news for DHCP scopes.  Maybe carves out a chunk of address range for it's self?  I dont know.

But as soon as I removed with 

C1121X-8PLTEP(config)#no app-hosting appid guestshell

I got my DHCP pool back, and the DHCP exclusion had disappeared.