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3529 - Troubleshoot DHCP option filter in NIOS

Scenario

A custom client has been deployed on the network 172.31.101.0/24 that requires vendor specific option (option 42), details listed in the table below. The network team has already setup the custom DHCP option space named IBDHCP, configured it with the 2 custom codes (10 and 15), and set up a filter to look for the special client IBEDU.sauron-2022_10_21.

Option Space

Option Number

Option Name

Option Type

Option Value

IBDHCP

10

Location

text

Santa Clara

IBDHCP

15

Server-IP

ip-address

198.10.9.13

However, client is not receiving these options. Please troubleshoot. You may use these 3 commands to help you on the testing-linux: 

  • To enable DHCP on the testing-linux, type: sudo set-network-dhcp

  • To disable DHCP on the testing-linux, type: sudo set-network-disable

  • To clear DHCP lease on the testing-linux, type: sudo clear-dhcp-leases

  • To show the current eth2 DHCP lease information, type: sudo show-dhcp-lease

When successfully configured, the command sudo show-dhcp-lease will print out the encapsulated options as follows:

CODE
 --- Encapsulated DHCP Options (vendor_encapsulated_options)
Decoding part 1: a:b:53:61:6e:74:61:20:43:6c:61:72:61
 Option ID: 10
 Option length: 11
 Option value: "Santa Clara"
Decoding part 2: f:4:c6:a:9:d
 Option ID: 15
 Option length: 4
 Option value: "198.10.9.13"

Estimate Completion Time

  • 25 to 30 minutes

Credentials

Description

Username

Password

URL or IP

Grid Manager UI

admin

infoblox

https://10.100.0.100/

Requirements

  • Administrative access to the Grid

Course References 

  • 3012: DHCP Troubleshooting Methodology

  • 3018: Configuring NIOS DHCP Option Spaces and Filters

Lab Initiation

Access jump-desktop

Once the lab is deployed, you can access the virtual machines required to complete this lab activity. To initiate the lab, click on the jump-desktop tile and login to the Linux UI:

Username: training

Password: infoblox

Initiate lab

To initiate the lab, double-click the Launch Lab icon on the Desktop.

Launch Lab

Launch Lab

Choose the lab number from the list and click OK.

After clicking OK, you will see a pop-up message with a brief description of the lab task. If the description looks correct, click Yes to continue lab initiation.

Lab initiation will take a couple of minutes to finish.

Once complete, you will see another pop-up message with the login credentials and the URL for the Grid Manager’s User Interface. Note that the credentials may differ from those from prior labs.

Screenshot 2024-05-06 at 3.16.57 PM.png

Tasks

To complete this lab, you need to perform the following tasks.

  1. Investigate and troubleshoot Custom Vendor Option delivery

Task 1: Troubleshoot DHCP Custom Vendor Option delivery

Check Option Space and Option Filter configuration to investigate why the Client is not getting the correct value in DHCP Option 43



Solutions

Task 1 Solution: Troubleshoot DHCP Custom Vendor Option delivery

sudo set-network-dhcp command will get the client a DHCP lease, but not the correct vendor-specific options:

CODE
$ sudo show-dhcp-lease

--- Raw DHCP Lease Information

lease {
  interface "ens160";
  fixed-address 172.31.101.252;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 43200;
  option dhcp-message-type 5;
  option dhcp-server-identifier 10.100.0.105;
  renew 1 2023/06/19 15:08:50;
  rebind 1 2023/06/19 20:53:49;
  expire 1 2023/06/19 22:23:49;
}

At this point, you should review the member configuration before running a traffic capture. The member configuration file (Data Management  DHCP  Member, select member, click Toolbar  View DHCP Configuration  IPv4) will show that the option space is properly setup, but in the network 172.31.101.0/24, these option values are not specified (blank).

If you navigate to the network 172.31.101.0/24, you will see that the fields under Custom DHCP Options are empty:

To properly finish the configuration, edit the network 172.31.101.0/24, click IPv4 DHCP options, under Custom DHCP Options, enter the correct values as shown below:

Screenshot_2024-07-05_15-12-07.png

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