SG500 - DHCP server does not assign predefined static IP addresses to hosts

[andbor600]

hi guys

I upgraded my SG500 switch firmware to 1.3.0.59, since there is a new functionality DHCP server v.4

well I must say I came accross the issue I cannot solve. DHCP server assign dynamic address - no hassles.

troubles start with static IP hosts.

I defined a couple of hosts with static address within the correct subnet. I tried with hardware address and client identifiers. no luck. my switch does not assign the IP address I assigned to the suitable mac address. to define it I use both CLI & Web.

no of them works. any idea ?

below the cut from my config:

ip dhcp pool host HP-Ellite
address 10.10.11.7 255.255.255.0 client-identifier 01:d8:d3:85:cf:09:72
client-name HP-Ellite
default-router 10.10.11.1
exit

ip dhcp pool host VAIO-Z
address 10.10.14.108 255.255.255.0 hardware-address 54:53:ed:1c:a1:46

default-router 10.10.14.1
exit

[kcnajaf]

Hi,

Have you checked what is the dhcp lease period configured? Try reducing the lease period to lesser value for testing and do a ipconfig/release and ipconfig/renew on the dhcp client.

Also you could try enter the client identifier in below format.

address 10.10.11.7 255.255.255.0 client-identifier 01d8.d385.cf09.72

Hope that helps.

Regards

Najaf

Please rate when applicable or helpful !!!

[andbor600]

hi Najaf

no, none of them works. I tried different values for lease time (refreshing my host with ipconfig release, ipconfig renew)

the client identifier syntax is not valid. I already had tried it. CLI does not accept client identifier seperated by "." (dot)

any other idea ?

look, this should be pretty straight forward... but is is not.

what is more there is no debug functionality have realy no idea what is wrong.

do you have a sg500 switch does it have dhcp server implemented ?

[vashkenazy]

Hi all... same problem here, with SG300-28. Did you solve?

[andbor600]

no, I did not.

as I wrote before ...

DHCP functionality is pretty easy.

I have been configuring it with other cisco devices. this one (firmware ?) does not work. I have no bloody idea ...

[vashkenazy]

Update. Still not working.

Actually in the image you can see the static assignment reservation (for client ID 01f0cba1c81b04, wich should have IP .110), and for the dynamic one, assigned wrongly by the switch (.101). It's supposed to be a firmware issue.

[vashkenazy]

It seems this firmware revision is quite buggy.

http://omgili.com/thread/.wHSUbtEfZS6sY9oec8tRj1DNafRV3e2EmgIsn2U7n.0aLwe7IPHyQOuQpaGjCA.V.Hsk_TfnUY-/

[gloidl]

A good day Gentlemen,

I will get straight to the answers of your questions

The fact is that the dynamic binding has a higher priority than static binding which we noticed already in our LAB and are currently working on this.

If the device gets an IP from DHCP next time it will ask for the same address it got previously. So even you configure the static host in the switch, the switch will still assign the former IP address to the device and will ignore your configuration. Therefore, clear, reboot, unplug things are very useful to make sure the switch will allocate the right static host address to the device.

Another thing is that the configuration of the MAC IP binding depends on the DHCP discover/request behaviour of the client being used.

Packets sent from the client, some devices send discover/request with option 61(client ID), some devices do not have this option but only have a MAC address.

When Option 61 is being used it has higher priority, than any configured static binding with a Hardware address,  Subsequently, the DHCP server will offer a new address to the client because there is no specific Client ID entry in the DHCP binding table because it only has a hardware address.

So, please check what your client actually does send!

Hope this clarifies matters.

Regards

[vashkenazy]

Hi Gunter, thanks for clarifications. Btw even if I set the client ID the switch doesn't assign correct IP (see picture above, you can see the same Client ID with an IP reserved, and with another IP assigned). The new firmware released today, 1.3.0.62, doesn't address the issue.

We're still hoping for fast bugfix.

Greetings

[Aleksandra Dargiel]

Hello Andrea,

You have to check if option 61 is in DHCP discovery packet send .

Another thing is the fact that the dynamic assignment has higher priority than the static one.

So the best workaround at this stage for you problem would be to clear MAC IP binding from the switch, reboot and unplug all DHCP clients.

When you connect client for the first time after reboot our switch would not have any old dynamic entry, only static IP binding and this should work as per binding.

Regards,

Aleksandra

[andbor600]

Aleksandra, Gunter

I am afraid I am not able to follow you,

where is this option 61 ?

I made tricks you called workarround. no success.

my example:

1. I assgined a static IP address (10.10.11.111) to a host with a specific client idenitfier

2. my host remained unplugged from my switch

3. I cleared ARP table

4. I cleared Dynamic Address table

5. I saved changes to my startup config

6. finally I rebooted my switch

7. I plugged my host to the switch

result ?

my host (running windows vista) cannot get IP address from switch DHCP server. finally the network card is assigned  with the following address: 169.254.110.130 255.255.0.0

as soon as I remove the static address assigned to my host's client identifier, my host gets a dynamic IP address from correct pool network.

any idea ?

[Tom Watts]

Andrea, you need to understand there is an ethernet client identifier. For microsoft ethernet id it is 01. Per RFC 1700 there is a list of client identifier that must be affixed before the mac address as dhcp option 61 is often inserted by the host (your computer) depending on the NIC.

Try 00 instead of 01.

If you want some help, email me at tmw0402@hotmail.com and we can do a team viewer.

-Tom
Please mark answered for helpful posts

[andbor600]

Tom, thnkas for a quick reply...

look, usually it is pretty easy to manage an issue with so precise instructions. but this particular time it is not.

as I understood the "dhcp option 61" is nothing more than "00" which go before pure hardware address.

so, coming back to my example from the first post

with this configuration, my switch assigns 169.254.110.130 255.255.0.0 address

ip dhcp pool host HP-Ellite
address 10.10.11.112 255.255.255.0 client-identifier 01:d8:d3:85:cf:09:72
client-name HP-Ellite
default-router 10.10.11.1
exit

with that configuration, my switch assigns 10.10.11.11 255.255.255.0 address

ip dhcp pool host HP-Ellite
address 10.10.11.112 255.255.255.0 client-identifier 00:d8:d3:85:cf:09:72
client-name HP-Ellite
default-router 10.10.11.1
exit

otherwords "00" does not work as explained (unless I misunderstood the meaing of dhcp option 61). my switch assigns first available dynamic IP address. atlhough the arp table is cleared, dynamic address table is cleared as well. swtich is rebooted, host is rebooted

once I change hardware address prefix to "01", my host asign itself 169.xxx.xxx.xxx adress.

[Tom Watts]

Hi Andrea, please email me a team viewer 8 code. I'll be happy to work on this with you and figure it out. All I ask is to basically let me do anything I want to your switch.

I have this working on win vista and win 7 in my lab using many different switches.

-Tom
Please mark answered for helpful posts

[Aleksandra Dargiel]

Hi Andrea,

Please note that IP address you have mentioned 169.254.110.130 255.255.0.0 is not coming from the switch but this is Microsoft APIPA mechanism indicating that there is problem with obtaining IP address from DHCP server.

For your network we need to take a look into the packet captures on particular DHCP clients.

If you would prefer you may also call Cisco Small Business Support line and open ticket with any of our engineers who would look into your network setup.

http://www.cisco.com/en/US/support/tsd_cisco_small_business_support_center_contacts.html

Regards,

Aleksandra