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DHCP Option 119 - any guidance on this?

DHCP Option 119 - any guidance on this?

DHCP Option 119 - any guidance on this?

2024-10-29 08:07:54 - last edited 3 weeks ago

Posts: 2

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Registered: 2024-10-29

DHCP Option 119 - any guidance on this?

2024-10-29 08:07:54 - last edited 3 weeks ago

Tags: #VLAN & Multi-Networks #DHCP Service #DNS

Model: ER605 (TL-R605)

Hardware Version: V2

Firmware Version: 2.2.6

Good morning,

i need help on the implementation of DHCP Option 119 in Omada.

I've setup a small Omada-network with 3 VLANs and Domainnames. Unfortunately the DHCP-Server is not providing a field to enter the Domain searchlist. So i have to use the custom options. I've tried several days all aproaches i could find in the internet. The result was always the same, it didn't worked. I have assigned 1 of the 3 VLAN to only one port on a switch. On this port I've connected a Windows Notebook. Whatever i enter for Option 119 for the dedicated VLAN and click on save has the result that all DHCP Server stop working. After deleting the option and save it needs a little bit and all DHCP-Server are back working.

I checked RFC3397 and aligned on this. I calculated the domainsearchlist to Hex String and Array. I've also taken care of the correct compression outlined in another RFC. I've also achieved that the domainsearchlist was shown line by line after "ifconfig /all" on my Notebook. A ping and nslookup showed that it's also not working.

I searched a lot on the internet but didn't find any guide on how to implement this on Omada. Highly appreciate any input. I'm also open for different solutions. Is there a possibility for example to define searchlist on DNS-Server (local like CoreDNS)?

thank you

Armin

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#1

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2024-10-29 08:38:08 - last edited 3 weeks ago

Posts: 5692

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Registered: 2023-06-09

Re:DHCP Option 119 - any guidance on this?-Solution

2024-10-29 08:38:08 - last edited 3 weeks ago

Hi @ContraVarus

Thanks for posting in our business forum.

You should set up the DHCP option custom and configure the hex and values to enable 119.

If this does not work, please provide your evidence by Wireshark which DHCP option is provided during the DHCP assignment (file or screenshot) along with your verification steps and diagram.

You should make sure the DHCP is released on this device.

No DNS server is built in the router yet.

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update! ☛Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.

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#2

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3 weeks ago - last edited 3 weeks ago

Posts: 2

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Registered: 2024-10-29

Re:DHCP Option 119 - any guidance on this?-Solution

3 weeks ago - last edited 3 weeks ago

Hi Clive,

really appreciate your input as this was guiding me to the correct way.

I tested around very much and monitored directly in Wireshark what is happening.

At the end i can confirm that the implementation of DHCP Option 119 in Omada is not like you mentioned or is defined in the respective RFC.

I translated several times my values by hand, by different calculators, tried every posibility with HEX-Values. At the end DHCP-Server delivered always Option119 to the clients but value for FQDN in the ACK-Packet was the same HEX-value i entered in Omada.

After this i changed in Omada the DCHP-Option 119 to String and entered only one domainname. After refreshing DHCP lease on Client DHCP-Option 119 was correclty filled as shown in Wireshark. Also on commandshell in windows Domainsearchlist was correctly used. I extended by another domain, seperated by "," as field is requesting ASCII-only and now i have a working Domainsearchlist with 3 different domainnames.

What I'm really angry about. I read before implementing this option all guides. I also read the whole RFC and tried around with these ugly HEX-codes. Also the RFC about the compressionmethod of the domainnames is just pain in the neck when you are calculating on your own by hand because i already didn't trusted all calculators in the web. As all said HEX i was never thinking about changing to STRING.

I hope i can save somebody else a little bit time or frustration with this explenation.

Thanks again Clive. Really appreciated your input.

Armin

Recommended Solution

1

1

#3

2 Reply

2024-10-29 08:38:08 - last edited 3 weeks ago

Posts: 5692

Helpful: 2734

Solutions: 1284

Stories: 0

Registered: 2023-06-09

Re:DHCP Option 119 - any guidance on this?-Solution

2024-10-29 08:38:08 - last edited 3 weeks ago

Hi @ContraVarus

Thanks for posting in our business forum.

You should set up the DHCP option custom and configure the hex and values to enable 119.

If this does not work, please provide your evidence by Wireshark which DHCP option is provided during the DHCP assignment (file or screenshot) along with your verification steps and diagram.

You should make sure the DHCP is released on this device.

No DNS server is built in the router yet.

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update! ☛Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.

Recommended Solution

1

1

#2

LV1

3 weeks ago - last edited 3 weeks ago

Posts: 2

Helpful: 1

Solutions: 1

Stories: 0

Registered: 2024-10-29

Re:DHCP Option 119 - any guidance on this?-Solution

3 weeks ago - last edited 3 weeks ago

Hi Clive,

really appreciate your input as this was guiding me to the correct way.

I tested around very much and monitored directly in Wireshark what is happening.

At the end i can confirm that the implementation of DHCP Option 119 in Omada is not like you mentioned or is defined in the respective RFC.

I translated several times my values by hand, by different calculators, tried every posibility with HEX-Values. At the end DHCP-Server delivered always Option119 to the clients but value for FQDN in the ACK-Packet was the same HEX-value i entered in Omada.

After this i changed in Omada the DCHP-Option 119 to String and entered only one domainname. After refreshing DHCP lease on Client DHCP-Option 119 was correclty filled as shown in Wireshark. Also on commandshell in windows Domainsearchlist was correctly used. I extended by another domain, seperated by "," as field is requesting ASCII-only and now i have a working Domainsearchlist with 3 different domainnames.

What I'm really angry about. I read before implementing this option all guides. I also read the whole RFC and tried around with these ugly HEX-codes. Also the RFC about the compressionmethod of the domainnames is just pain in the neck when you are calculating on your own by hand because i already didn't trusted all calculators in the web. As all said HEX i was never thinking about changing to STRING.

I hope i can save somebody else a little bit time or frustration with this explenation.

Thanks again Clive. Really appreciated your input.

Armin

Recommended Solution

1

1

#3

2024-10-29 08:07:54 - last edited 3 weeks ago

Posts: 2

Helpful: 1

Solutions: 1

Stories: 0

Registered: 2024-10-29

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VLAN & Multi-Networks DHCP Service DNS