DHCP option 15

[Mahesh_Gaur]

Hi, I am planning to upgrade my L3 switch and want to use DHCP option 15. Please suggest Meraki 9300-M switch support DHCP option 15 ? As its not supported on MS390. 

[alemabrahao]

In the DHCP server settings you must add a new options as Custom Text and configure it with the desired domain.

15

Domain Name

This option is used to carry the “domain” portion of a node’s Fully Qualified Domain Name. (FQDN) Example: “meraki.com” of mail.meraki.com.

[alemabrahao]

I don't know where you read this, but it is supposed to be supported on all Siwtch L3 models.

https://documentation.meraki.com/General_Administration/Cross-Platform_Content/Setting_Custom_DHCP_O...

https://documentation.meraki.com/MS/Layer_3_Switching/MS_Layer_3_Switching_and_Routing

[Mahesh_Gaur]

As per the Cisco TAC MS390 not supported DHCP Option 15.

[Ryan_Miles]

I just tried on a C9300-M. Same error as a MS390.

I don't have any background on why it's not supported. I see several old threads about various IOS versions on routers and switches not supporting either.

[Mahesh_Gaur]

Can you please confirm MS350 support DHCP option 15 ??

[Ryan_Miles]

Tested and dashboard appears to allow the config for MS (classic Meraki) switches and MX's.

[Mahesh_Gaur]

yes, I tested on MS250 and it is supported. So just want to cross validate the same for MS350 switch.

[ww]

I have had the mx allow dhcp config options but they would not work. Then support told me not al options are supported on mx.  It would be good to have a list of which work on what platform

[PhilipDAth]

On a Cisco IOS or IOS-XE device, you instead use the "domain-name company.com" command.  e,g.:

ip dhcp pool dhcppool
 network 192.168.1.0 255.255.255.0
 default-router 192.168.1.254
 domain-name company.com
 dns-server 192.168.1.254
 lease 7
 update arp

[alemabrahao]

So you must correct your documentation @Ryan_Miles 

[Mahesh_Gaur]

@alemabrahao - MS390 support DHCP server but not support DHCP option 15 same has been validated by Cisco Meraki TAC

[alemabrahao]

@Mahesh_Gaur 

@Ryan_Miles 

I believe the support is wrong, as the documentation is very clear that it supports the DHCP server as you can see.

Either the documentation is wrong or the support is wrong.

The documentation also makes it very clear that ALL L3 switches are supported.

Check out the links I sent you. Again support or documentation one of them is wrong.

[ww]

That dhcp doc have not been updated for 3 years 

[alemabrahao]

Yes, I saw, it explains a lot.

I can understand it, because a Nexus Switch, for example, only does relay, but in this case it justifies it because it is a data center switch.

But in this case, this is information that should have been corrected a long time ago, people often rely on documentation when making a purchase or commercial proposal, so this is relevant information to be added.

If not, it becomes that old expectation vs reality.

[cmr]

@alemabrahao the MS390 and C9300-M do support being a DHCP server, it is only that you cannot specify option 15 which is the domain.  That is a bit of a problem in any Windows network...  We've just bought two C9300-Ms so they might be going back!  The option definitely works on MX and MS 355X switches.

[alemabrahao]

@cmrI know it's supported, I just gave an example. Even so, I still don't see the point.

[DarrenOC]

Ouch - that’s bit of a gotcha.

Why would some of the legacy Meraki switches support such basic DHCP options yet the newer devices not?

[cmr]

I'm guessing that it might be because the IOS-XE switches have a specific named option for 15, as per this config below:

ip dhcp pool xxxx_pool
  network 10.xxx.xx.0 255.255.255.0
  default-router 10.xxx.xx.1
  dns-server 10.xxx.x.xxx 10.xxx.x.xxx 10.xxx.x.xxx 10.xxx.x.xxx
domain-name xxx.local
netbios-name-server 10.xxx.x.xxx 10.xxx.x.xxx
netbios-node-type h-node
option 119 hex xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx
option 165 ascii "xxxxxxx.xxx.local:443"
option 166 ascii "xxxxxxx.xxx.local:1883"
option 167 ascii "FALSE"
option 199 ascii "xxxx-xxxx-xxx-xx-xxxx"
lease 0 10

[cmr]

@Ryan_Miles can you please try options 44 and 46 on your C9300-M (netbios-name-server and netbios-node-type) and see if they are allowed?

[cmr]

Another option (pun intended) is to use option 119 where the domain search space is entered in hexadecimal.  This works on an MS355X stack, @Ryan_Miles are you also able to test the domain in there on a C9300-M?

[Ryan_Miles]

44 & 46 not supported (presents error) on MS390/C9300-M.

119 appears to be supported.

[cmr]

Thanks @Ryan_Miles, so it seems that you cannot use the options that are named in IOS-XE as opposed to the ones where IOS-XE needs the option number.  Can this please be logged as a high priority bug as it does somewhat damage the Meraki switch product path!?! 

We have just bought a pair of C9300-Ms to test with and were going to buy many more, but if this isn't fixed then I think we'll have to return them as faulty... 😞

[Ryan_Miles]

My recommendation is open a Support case to have this logged & confirmed.

[cmr]

@Mahesh_Gaur can you please try to add options 44 and 46 to your MS390 to confirm that they also don't work and point the support team to this discussion?  I am next in the office on Wednesday so would likely be able to log a support case only on Thursday next week.  As we need some action, that might help speed things up!  I am happy to also log one then.

[Mahesh_Gaur]

@cmr - I don't have MS390 so I am not able to test. I tested the same on MS250 and its working. but now I am planning to upgrade my MS250 with MS390/ C9300-M.

That's why looking for support on DHCP option 15 ??

[cmr]

Apologies @Mahesh_Gaur I thought you'd logged a ticket about a device you had, I'll log one next week with ours.