Option 43 with Suboption 21

[Mohammad Ali]

I have a Cisco ME switch and I am trying to figure out the Option 43 with Suboption 21 configuration. I need to point the AP to two different servers so first one requires sub option 06 (HEX) and second one requires sub option 15(HEX).  I have done that but it isn't working.  So far I have tried:

06....IP15...IP

Is there any other format that is needed perhaps I am missing some thing here.  Thank you.

[balaji.bandi]

as per last time i have tested with some Meraki devices (my IP example - 202.63.96.9)

HEX for 32:30:32:2e:36:33:2e:39:36:2e:39

06:15:IPHEXHERE:2c:15:IPHEXHERE

[Mohammad Ali]

Thank you I tried that with the 2C = , but same results. Did that in Meraki as well as Cisco IOS with same results. When I look at the packet capture and expand DHCP Option 43 I do not see any sub option in there instead both IP's show up under 43 only.

[Mohammad Ali]

Here is a quick example

[rais]

Option 43 sub-options are sent as TLV:

<option-code><length><value><seperator> <option-code><length><value><seperator> etc.

So in your case it should be:

06 <length may be 0x20 for 32-bit IP><Your IP Address for 0x6> 00 15 <length for 32-bit IP><Your IP Address for 0x15> 00

https://tools.ietf.org/html/rfc2132#section-8.4

HTH.

[rais]

Option 43 sub-options are sent as TLV:

<option-code><length><value><seperator> <option-code><length><value><seperator> etc.

So in your case it should be:

06 <length may be 0x20 for 32-bit IP><Your IP Address for 0x6> 00 15 <length for 32-bit IP><Your IP Address for 0x15> 00

https://tools.ietf.org/html/rfc2132#section-8.4

HTH.

[Mohammad Ali]

Thanks so if you look at the screen shot I have already tried that. I noticed after the first IP you have "00" and then "15" instead of "2c which is a comma". Any specific reason you are adding a "0" in Hex in between two IP's?

[rais]

I believe after after TLV there is a separator which is 0x00.

[Mohammad Ali]

So I think separator between the two IP's would be a "," HEX = 2C

06 <length may be 0x20 for 32-bit IP><Your IP Address for 0x6> 2C 15 <length for 32-bit IP><Your IP Address for 0x15>

Also not sure if the 00 is needed at the end either. wouldn't that be like just inserting a "0" in between two IP's and a "0" towards the end something like:

10.10.10.10020.20.20.200

It will totally change the IP address.