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SG300-28P Running - DHCP Problems

I have a SG300-28P running which is configured in L3 mode.  This unit is running its DHCP service for my LAN hosts.

I've only set up a part of my /24 LAN subnet as the DHCP scope and have statically configured a number of LAN hosts to use specific IP addresses in this subnet, based on MAC address.  For these reserved addresses I have used addresses outside the range used for the DHCP scope.

Here's an example:

ip dhcp server
ip dhcp pool host some-host-1
address hardware-address b8:c7:5d:c7:f9:5e
ip dhcp pool host some-host-2
address hardware-address 20:c9:d0:9a:a2:fb
ip dhcp pool network LAN
address low high
domain-name home.local

However, what I'm seeing is the static hosts are being allocated addresses from the thru 253 block (with the MAC Address/Client Identifier being shown with the correct MAC address but with a "01:" prefix).

Also I'm seeing a few (declined) entries which look similar to this " Client Identifier c0.a8.6f.e2 2014-Mar-18 12:01:24 Dynamic Declined", i.e. with a MAC address with just a XX.XX.XX.XX hex format.

Any thoughts.


Everyone's tags (1)

Hi Ian, I believe you may not

Hi Ian, I believe you may not be using client identifer correctly. Use the client-identifer command and affix the 01 or the 00 in the command string.


client-identifer 01:20:c9:d0:9a:a2:fb

See if this will work.

-Tom Please mark answered for helpful posts
New Member

Hi Tom,I changed my statics

Hi Tom,

I changed my statics from "hardware address <mac address>" to "client identifier 01:<mac address>" and that seems to work.  What I don't understand is what was wrong with my MAC address configuration.

Also I'm still seeing some strange declined entries with short MAC addresses (i.e. XX.XX.XX.XX).

Thanks again. 

New Member

I've done some more testing

I've done some more testing.

So using "address <ip-address> <subnet> hardware-address <mac address>" doesn't work.

Using "address <ip-address> <subnet> client-identifier 01<mac address>" does match the IP to the MAC but then the default gateway & dns settings are not inherited from the DHCP scope.

so I have to have configuration like this for every static host:

ip dhcp pool host <name>
address <ip-address> <mask> client-identifier 01<mac-address>
default-router <ip-address>
dns-server <ip-address>




New Member

Hi Ian, I did test this issue

Hi Ian,


I did test this issue with my own switch. I got same issue as well.  Please contact Cisco support center. 1-866-606-1866




New Member

I am having almost the same

I am having almost the same problem on Cisco SG300-28.

-Single default VLAN1 in L3 with 192.168.100.x/24 network, Switch IP
-Router/ISP modem's running NAT with LAN IP
-DHCP configured and assigning IP addresses to client machines from start of pool
-But static reservations for client machines is NOT working with MAC/hardware addresses, haven't tried with Client IDs yet.

Q1-Is only option to configure static reservations is through client IDs?
Q2-If so what will be the client IDs for MacBookPro, iphones and android devices? (I understand that windows devices have client IDs as 00 & 01:MACaddress
Q3-Do I have to make each static entry with Default-Router & DNS for all devices when using Client IDs? (I already have pool configured to assign default gateway and dns , which works well with dynamic DHCP clients)

P.S. I am doing all configuration through GUI, am I missing out on any important feature via GUI?


New Member

Same issue here - when trying

ok - found a solution to a very similar, but not quite the same issue. So if someone has issues with assignind static ips via DHCP take a look at this post:

Long way short: Don't enter a "Client Name". That makes the difference!

Works like charm then... THANK YOU for this.

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