DHCP router refuses to give out addresses for specific VLAN.

JLAW904

I'm pulling my hair out with this one and I have no idea what's causing this. Basically I have a router set up with two switches connected via EtherChannel trunks for VLANs 64, 66, and 69. The Router is to hand out addresses for them. It works fine for VLANs 64 and 69. A client can get address on those switch access ports. But if I try to get a device on an access port for VLAN 66 to use DHCP, it won't get the address. I used the DHCP debug output and see some errors:

*Mar 1 00:21:08.455: DHCPD: Sending notification of DISCOVER:
*Mar 1 00:21:08.459: DHCPD: htype 1 chaddr c205.0124.0000
*Mar 1 00:21:08.459: DHCPD: remote id 020a00000a01420113000042
*Mar 1 00:21:08.459: DHCPD: circuit id 00000000
*Mar 1 00:21:08.459: DHCPD: DHCPDISCOVER received from client 0063.6973.636f.2d63.3230.352e.3031.3234.2e30.3030.302d.4661.302f.30 on interface Vlan66.
*Mar 1 00:21:08.459: DHCPD: Seeing if there is an internally specified pool class:
*Mar 1 00:21:08.459: DHCPD: htype 1 chaddr c205.0124.0000
*Mar 1 00:21:08.459: DHCPD: remote id 020a00000a01420113000042
*Mar 1 00:21:08.459: DHCPD: circuit id 00000000
*Mar 1 00:21:08.459: DHCPD: Allocate an address without class information (10.1.66.0)
*Mar 1 00:21:08.459: DHCPD: subnet [10.1.66.1,10.1.67.254] in address pool VLAN66 is empty.
*Mar 1 00:21:08.459: DHCPD: Sending notification of ASSIGNMENT FAILURE:
*Mar 1 00:21:08.459: DHCPD: htype 1 chaddr c205.0124.0000
*Mar 1 00:21:08.459: DHCPD: remote id 020a00000a01420113000042
*Mar 1 00:21:08.459: DHCPD: circuit id 00000000
*Mar 1 00:21:08.459: DHCPD: Sending notification of ASSIGNMENT_FAILURE:
*Mar 1 00:21:08.459: DHCPD: due to: POOL EXHAUSTED
*Mar 1 00:21:08.459: DHCPD: htype 1 chaddr c205.0124.0000
*Mar 1 00:21:08.459: DHCPD: remote id 020a00000a01420113000042
*Mar 1 00:21:08.459: DHCPD: circuit id 00000000

It's acting like all the addresses are used up, right? Why?? If I do a "sh ip dhcp binding" or "conflict", nothing comes up for that VLAN. Any ideas?

(This is in GNS3 by the way.)

And here's my DHCP pool config:
ip dhcp pool VLAN64
network 10.1.64.0 255.255.254.0
dns-server 4.2.2.2 4.2.2.3
default-router 10.1.64.1
option 150 ip 10.1.68.8
ip dhcp pool VLAN66
network 10.1.66.0 255.255.254.0
dns-server 4.2.2.2 4.2.2.3
default-router 10.1.66.1
ip dhcp pool VLAN69
network 10.1.69.0 255.255.255.0
dns-server 4.2.2.2 4.2.2.3
default-router 10.1.69.1

arrogantbastard

What did you configure for excluded addresses?

Magic Johnson

If you configure a pool, without any excluded addresses, and your router has been assigned the first available address (like in this config) does iOS assume the address pool has been exhausted or does it give the next available? I can't even remember sorry.

xnx

IOS should know the interface of the router and not allocate that address so this shouldn't be a problem here.

Magic Johnson

xnx wrote: »

IOS should know the interface of the interface of the router and not allocate that address so this shouldn't be a problem here.

Yeah I just did a bit of reading and it does automatically exclude it from the pool. Have got my head wrapped around icnd2 topics so much I'm slightly forgetting icnd1 topics!

EDIT: OP give us a show ip dhcp pool to review.

JLAW904

sh ip dhcp pool:
Pool VLAN64 :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 510
Leased addresses : 1
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased addresses
10.1.64.11 10.1.64.1 - 10.1.65.254 1

Pool VLAN66 :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 510
Leased addresses : 0
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased addresses
10.1.66.1 10.1.66.1 - 10.1.67.254 0

Pool VLAN69 :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 0
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased addresses
10.1.69.1 10.1.69.1 - 10.1.69.254 0

JLAW904

arrogantbastard wrote: »

What did you configure for excluded addresses?

Thank you. That was the problem. I looked it over several times before but didn't notice I made a typo. I had:

ip dhcp excluded-address 10.1.64.1 10.1.64.9
ip dhcp excluded-address 10.1.64.101 10.1.65.255
ip dhcp excluded-address 10.1.66.1 10.1.67.9 <<< Should be 10.1.66.1 10.1.66.9
ip dhcp excluded-address 10.1.66.101 10.1.67.255
ip dhcp excluded-address 10.1.69.1 10.1.69.9
ip dhcp excluded-address 10.1.69.101 10.1.69.255

So basically my 2 statements for vlan 66 were excluding the entire pool. I can't believe how much time I spent messing with this lab and missed that.