Introduction

A Host record allows a single primary Name (fully-qualified domain name) to be associated with any of the following, managed collectively in Grid Manager as a single database object:

• one or more IPv4 addresses, which manifest as matching pairs of A and PTR records
• one or more IPv6 addresses, which manifest as matching pairs of AAAA and PTR records
• one or more Host Aliases, which manifest as CNAME records pointing to the primary name
• optional DHCP fixed address configuration for each IP address

Note that publishing multiple A records for the same name (by adding more than one IPv4 address to a Host) or multiple AAAA records for the same name (by adding more than one IPv6 address to a Host) is legal and results in “round-robin DNS” behavior.

Host records provide several advantages compared to managing an equivalent collection of Stand-alone DNS Records, the most important of which is that if you change one part of a Host record, the other parts will automatically update to stay in sync.

The trade-off is that you must be VERY careful when deleting a Host record!

myprefix-192-168-1-10.sandbox.illinois.edu. IN A 192.168.1.10
myprefix-192-168-1-11.sandbox.illinois.edu. IN A 192.168.1.11
...
10.1.168.192.in-addr.arpa. IN PTR myprefix-192-168-1-10.sandbox.illinois.edu.
11.1.168.192.in-addr.arpa. IN PTR myprefix-192-168-1-11.sandbox.illinois.edu.
...

Introduction

A DHCP Fixed Address makes a particular IP address available for use exclusively by a single designated client.  For as long as the Fixed Address is configured, the designated client will always receive this IP address when connected to the appropriate network, and this IP address will never be allocated to any other client.  For DHCPv4, the designated client is identified by MAC address; for DHCPv6, it is identified by DUID (DHCP Unique Identifier – see also Limitations of DHCPv6 fixed address allocation).

From the client’s point of view, obtaining a lease from a Fixed Address is exactly the same as obtaining a lease from a DHCP Range.

On the server side, however, there is an important difference: fixed addresses are timeless, which is to say that the server’s behavior does not take into account whether the IP address in question was previously leased (either to the same client or to a different client).  This has two practical consequences for the careful network administrator wishing to avoid an operational conflict:

• Avoid configuring a Fixed Address for an IP which currently has an Active lease belonging to a different client (unless you are certain that the old client is no longer on the network).
• Avoid configuring a Fixed Address for an IP which very recently had a Fixed Address belonging to a different client (unless you are certain that the old client is no longer on the network).

Stand-alone Fixed Addresses vs DHCP-enabled Host records

The stand-alone DHCP Fixed Address objects described on the remainder of this page are DHCP-only objects with no DNS component.

You may alternatively wish to consider enabling DHCP for an IP address within a Host record, which is functionally equivalent to creating a stand-alone Fixed Address but makes it easy to keep the DNS and DHCP configuration for a client in sync (in case you later decide to migrate the client to a different IP address or retire it altogether).

Reservations

You may notice that it’s also possible in IPAM to create a “Reservation” object.  This is not the same thing as a Fixed Address, and will not accomplish what you probably intend; a “Reservation” in IPAM is a placeholder which does not permit any DHCP client to use the IP.

Users familiar with Microsoft DHCP should note that a Microsoft DHCP “Reservation” is analogous to a Fixed Address in IPAM, not a “Reservation”.

Creating a DHCP Fixed Address

To create a new stand-alone DHCP Fixed Address:

1. Using either DHCP View or IPAM View, Open the Network in which you want to add a fixed address (see Getting Started with IPAM).
2. Optionally (if using IPAM View), select the checkbox next to the desired IP address.
3. Click the dropdown arrow next to the Add (+) icon above the table in the main workspace, then choose “Fixed Address”.
4. Click “Next” at the bottom of the dialog window.
5. Enter the desired IP address.

   If you have opened a Network in IPAM View and selected an IP address in the main workspace, it will automatically be pre-populated for you.

6. For IPv4 addresses: ensure that “MAC Address” is selected, and enter the MAC address of the client that will use this IP.
7. For IPv6 addresses: ensure that “DUID” is selected, and enter the DHCP Unique Identifier of the client that will use this IP (see also Limitations of DHCPv6 fixed address allocation) .  Do not use “MAC Address” for IPv6 Fixed Addresses as this option is not yet supported by most building routers on our campus.
8. Optionally, you may use the Name field to specify an internal display name for this Fixed Address object.

   The Name field does not create a DNS hostname! If you want to manage DNS and DHCP for this client together, consider adding DHCP to a Host record instead of creating a stand-alone Fixed Address.

9. Click “Save & Close”.

Please note that your network must have autoconfiguration service appropriately enabled (see Requesting DHCP for Networks) in order for creating a DHCP Fixed Address to have any effect.

Editing a Fixed Address

To edit an existing stand-alone DHCP Fixed Address:

1. Navigate to the Fixed Address you want to edit (e.g. by opening its Network in DHCP View, or opening the individual IP address in IPAM View to display Related Objects – see Getting Started with IPAM).
2. Select the checkbox for the Fixed Address object, and click the Edit (notepad) icon above the table.
3. Make sure to enable Advanced Mode for the dialog.
4. Make any desired changes.
5. Click “Save & Close”.

Note that you can configure custom DHCP options that will apply only to this individual fixed address (but are otherwise similar to Setting DHCP Options for a Range).

Deleting a Fixed Address

To deleted an existing stand-alone DHCP Fixed Address:

1. Navigate to the Fixed Address you want to edit (e.g. by opening its Network in DHCP View, or opening the individual IP address in IPAM View to display Related Objects – see Getting Started with IPAM).
2. Select the checkbox for the Fixed Address object (making sure no other checkboxes are selected), and click the Delete (trash can) icon above the table.
3. If you’re sure, click “Yes” when the confirmation dialog appears.

This page contains information about navigating the Grid Manager web interface once you have logged in.

Logging In

See How do I log in?

Getting Help

If you have a question not covered by this service documentation, you can try one of the following resources or contact hostmgr for assistance.

Help Panel

All screens and dialog windows in Grid Manager contain context-sensitive help, which appears in the Help panel on the far right-hand side of the window.

1. If the Help panel is not visible, click the grey “?” icon on the far right to expand it.
   
2. Some Help panels contain vertically expanding subpanels.  Expand the subpanel labeled “Help” to see context-sensitive help for the screen you are on.
3. When you don’t need the Help panel, you can collapse it again to save space.

Vendor Documentation

Extensive vendor documentation for Grid Manager is published in HTML and PDF formats.

Please note that not all functionality described in the vendor documentation is available to you in the University of Illinois IPAM service.

Browser Information

The vendor documentation includes requirements for your workstation (including minimum display resolution) and known limitations for certain browsers.

A few general tips:

• Please be patient with the web interface; occasionally it will take a few seconds to finish refreshing after you have clicked on something. Clicking repeatedly will not help, and in fact will probably make you wait longer for the interface to catch up.
• Don’t use your browser’s Back button within Grid Manager.
• Don’t use Grid Manager in multiple tabs or windows of the same browser, as they may interfere with each other.
  (However, we have had success using Grid Manager concurrently in two separate browsers, e.g. in one instance of Chrome and one instance of Firefox.)

The list of OS and browser versions tested and validated by the vendor is now maintained in the release notes (which are not publicly viewable), but generally includes recent releases of Firefox, Chrome, Safari, and Edge.  Let us know if you consistently experience problems with the latest version of any of these browsers, and also whether the problem is solved by using a different browser.  Note that Mozilla offers a Firefox Extended Support Release (ESR) which may be helpful in some circumstances.

Basic Navigation: a Guided Tour

Upon first login, Grid Manager will display the (fairly sparse) Tasks Dashboard, which doesn’t do much but serves as a landing page.

To illustrate some basic principles of Grid Manager navigation, we’ll begin by browsing Networks in DHCP View.  This is not what you’ll usually do in practice, but it’s the simplest place to start.

Browsing Networks in DHCP View

To display Networks in DHCP View:

1. Choose “Data Management” from the top row of tabs.
2. Choose “DHCP” from the second row.
3. Choose “Networks” from the third row.
4. Choose “Networks” from the fourth row.

This will display a table containing all Networks that you have permissions on.

Using the Table Controls

Just above the table in the main workspace is a row of icon buttons.  Mouse over each icon in turn to see their names:
Open, Add, Edit, Delete, Export, and Print.

• To Edit a Network from the table, select the checkbox to its left, and then click the Edit (notepad) icon above the table.

  screenshot

  

  This opens the Edit Network dialog box. You don’t have permissions to change anything in the Edit Network dialog box, but you can use it to examine the DHCP configuration properties of your Network.  To close the dialog box and return to the table, click Cancel (in the lower left).

• To Open a Network from the table, just click directly on its address/CIDR (e.g. “192.168.0.0/26”) in the Network column.  Alternatively, you could select its checkbox and then click the Open (right arrow) icon above the table.  Opening a Network takes you to a new screen which we will discuss in the next section.

The hamburger menu icon in each table row displays a shortcut menu which provides yet another way to Open or Edit the Network in that row.

If your table contains too many rows to display all at once, you can

• use the page navigation buttons (below the table, on the left) to page through them.
  

• start typing the first several characters of a network address e.g. “192” into the “Go to” box (above the table, on the right) to quickly select a matching row. 

  “Go to” only matches one field (whichever one Grid Manager considers to be the primary identifier), so you can’t use it to find e.g. Network Name even if you have added a Network Name column to the table.

• click “Show Filter” and Apply desired filter criteria to display fewer results.  (Note that you can Filter based on Network Name.)

  screenshot

  

Opening a Network (DHCP View)

When you Open a Network as described above, the main workspace displays a new table containing all DHCP-related objects (Fixed Addresses, Ranges, and DHCP-enabled Hosts) that have been configured within that Network.

From here you could go on to perform a variety of DHCP configuration tasks.

For now, just familiarize yourself with the following new interface elements near the top of the main workspace:

• The breadcrumb link “Networks Home” (just below the four rows of navigation tabs) may be used to return to the list of all Networks.
• Next, Grid Manager displays the currently opened object (“192.168.0.0/26”) and its type (“IPv4 Network”).

• Click the nearby blue pencil Edit icon to Edit the currently opened object.

  Note the difference between this blue pencil Edit icon which edits the currently opened object, and the notepad Edit icon further down which edits the object whose checkbox is selected from the table.
• Click the Bookmark (red swallowtail flag) icon to bookmark the currently opened object so you can quickly navigate back to it later (see Advanced Tips and Tricks).
• Click “Go to IPAM View” to Open the current Network in IPAM View (discussed further down) instead of DHCP View.  This is a convenient way to quickly switch between these two views of the same Network.

Opening a Zone

When you open a DNS Zone object as described above, the main workspace displays a table containing either the Records or the Subzones within that Zone (depending on which tab you select from the fourth row underneath the Zone name).

Note the following controls near the top of the main workspace:

• Multiple breadcrumb links allow quick navigation to any ancestor of the current zone, including the DNS View (“default”).  “DNS Home” may be used to return to the list of Views.

• Click “Toggle flat view” on the Records tab to change the way Host records are displayed in this table.  After you click it, the link text changes to “Toggle hierarchical view”.

  We recommend using Flat view for the Records tab, to ensure that you will always see all manifestations of Host records.

• Optionally (and independently), click “Toggle flat view” on the Subzones tab to display all descendants of the current zone instead of only its immediate children (note that this may cause the interface to respond more slowly).  Navigate back up to “edu” for a clear illustration of the difference.

Browsing Networks in IPAM View

IPAM View is another way of looking at Networks.  Whereas DHCP View is narrowly focused on DHCP functionality, IPAM View combines configuration data from both DNS and DHCP into a holistic picture of how every IP address in a network is being used (or not – it also displays unused IPv4 addresses).  IPAM View also shows Network Containers which organize Networks into a hierarchical tree structure.

To browse Networks and Network Containers in IPAM View (again, this is intentionally not the quickest method):

1. Choose “Data Management” from the top row of tabs.

2. Choose “IPAM” from the second row.

3. The main workspace will display any top-level Network Containers (shown with a folder icon) which contain at least one Network that you have permissions on.  Note that you don’t have permissions on the Network Container itself, so you can’t see any other details about it.

   screenshot

   

   This is a separate table from the one we saw earlier in DHCP View, so you’ll want to add the Network Name column again here.

4. Open a Network Container by clicking its address/CIDR.  At this point a third row of tabs appears with “Net Map” selected by default, and the workspace displays a graphical visualization of the contents of this Network Container (which may include other Network Containers and/or leaf Networks), subject to your permissions.

5. Choose “List” from the third row of tabs to display the contents of this Network Container in a table instead.

   screenshot

   

   Note that Network Containers have a folder icon, while leaf Networks have an icon with no folder.  There is also a “Toggle flat view” link which behaves similarly to the one described above for DNS Subzones.

6. Open a leaf Network by clicking its address/CIDR.

Opening a Network (IPAM View)

When you open a leaf Network in IPAM View, you can choose “IP Map” from the third row of tabs to display a graphical representation of how each address in the network is used, or choose “List” to display the addresses in a table (generally more useful).

From here,

• Click “Go to DHCP View” to open the current Network in DHCP View (instead of IPAM View).  This is a convenient way to quickly switch between these two views of the same Network.

  In general IPAM View is more powerful, but some DHCP configuration tasks can only be performed (and others are easier) in DHCP View.

• If you select an IP address which is used by only one object, you can click the Edit (notepad) icon above the table to Edit that object.

• Open an IP address (by clicking on it in the table) to display all of its Related Objects in a new table where you can Edit or Delete them individually.  Use the breadcrumb links to return.

  screenshot

  

• Be very careful with the Reclaim button (see Reclaiming Objects Associated with IPv4 and IPv6 Addresses in the vendor documentation).  When in doubt, it’s safer to examine the Related Objects individually and make a decision about whether to edit or delete each one.
• Please do not use the Ping button (see known issues involving Discovered Data).

Global Search

The step-by-step browsing methods above are very helpful for learning how Grid Manager works, but they aren’t usually the quickest way to reach your goal.  Grid Manager provides several practical navigation shortcuts, the most important of which is Global Search.  (Some others will be discussed later in Advanced Tips and Tricks.)

Click the Search (magnifying glass) button in the upper right-hand corner of the interface window to open the Search dialog box.

Use Basic Search to quickly locate objects matching a specific IP address, MAC address, or DNS Name:

1. Select the “Basic” tab.

2. Click the left-most drop-down (“Choose Filter”) and select DNS Name, IP Address, or MAC Address.
3. Optionally select a different operator from the middle drop-down.

4. Type the desired search value in the text box on the right.
   Please note:

   • MAC Address values should be punctuated with colons, e.g. “aa:aa:aa:00:00:10“

   • When searching by DNS Name, try to use at least a partially-qualified name.  For example, searching for “www.techservices” is much more efficient than searching for “www“.

5. Click “Search”.
   (see screenshot under examples below)
   

or use Advanced Search for other types of searches:

1. Select the “Advanced” tab.

2. In the first filter criterion (Type equals All), click the right-most drop-down (All) to select what type of objects you want the search to return, such as “All Networks” or “All Zones”.

   If you do not filter by Type, then by default Grid Manager will search ALL objects in its database. While you might need to do this on rare occasions (if you aren’t able to find what you want using a more specific search), it takes a lot longer, and is also more likely to return a large number of uninteresting results.

3. Type your desired search value into the main (unlabeled) text box above the filter criteria.  You can enter a regular expression in this field; see Supported Expressions for Search Parameters in the vendor documentation for details.

4. Check “Include Extensible Attributes Values” in case the value you are searching for appears in an extensible attribute (such as Network Name).  If you leave this unchecked, only built-in object fields will be searched.

5. Optionally click “+” to add more filter criteria.
6. Click “Search”.
   (see screenshot under examples below)

Once your search results are displayed, you may:

Bookmarks

Grid Manager allows you to bookmark an object (zone, network, etc) and easily navigate back to it later. This is a good way to quickly access your most commonly used objects.

Adding bookmarks:

1. Open the object you wish to bookmark, so its name or identifier is displayed near the top of the main window (see Getting Started with IPAM).
2. Click the Bookmark (red swallowtail flag) icon to add a new bookmark for this object.

   screenshot

   

Using bookmarks:

1. Locate the Finder panel on the far left-hand side of the window; if it is currently collapsed, click the gray folder icon to expand it.
   
2. Expand the “Bookmarks” subpanel.

   screenshot

   

3. Click on the name of a bookmark to immediately navigate to the object.

You can also hover over a bookmark and click the Edit (blue pencil) icon to change its name, or the Delete (trash can) icon to delete it.

Smart Folders

The following smart folders can provide you with quick, convenient access to your own domains and networks (the ones for which you are listed in Contacts Database), but they require a one-time set up for each user account.

Setting up the My Domains smart folder

1. Navigate to Smart Folders > Global Smart Folders using the rows of tabs at the top of the screen.
2. Select the global smart folder named “My Domains”.
3. Click “Save Copy As” to create your own personal copy of this smart folder named “My Domains Copy” under Smart Folders > My Smart Folders.

   screenshot

   

4. Click the Edit (blue pencil) icon to edit “My Domains Copy”.
5. In the last filter criterion (CDB Permission equals NETID), replace “NETID” by your netid.
6. Click the “Save” button (not “Save Copy As”) to save your changes.

   screenshot

   

Setting up the My Networks smart folder

1. Navigate to Smart Folders > Global Smart Folders using the rows of tabs at the top of the screen.
2. Select the global smart folder named “My Networks”.
3. Click “Save Copy As” to create your own personal copy of this smart folder named “My Networks Copy” under Smart Folders > My Smart Folders.
4. Click the Edit (blue pencil) icon to edit “My Networks Copy”.
5. In the last filter criterion (CDB Permission equals NETID), replace “NETID” by your netid.
6. Click the “Save” button (not “Save Copy As”) to save your changes.

Using Smart Folders

1. Locate the Finder panel on the far left-hand side of the window; if it is currently collapsed, click the gray folder icon to expand it.
   
2. Expand the “Smart Folders” subpanel.
3. Click the (+) icon to the left of a smart folder (e.g. My Domains or My Networks) to expand its contents within the Finder panel.
4. For smart folders with grouped results (e.g. My Networks), click the (+) icon to the left of a result group (e.g. network name) to show the individual objects (e.g. network CIDRs).

   screenshot

   

5. Click on a domain name or a network CIDR to navigate directly to the corresponding Zone or Network object.

Using the Toolbar panel

The Toolbar panel on the right-hand side of the main window (just to the left of the Help panel) provides many convenient shortcuts for the experienced IPAM user.

For example, you can use the Toolbar’s Add menu to create DNS Records, DHCP Ranges, and even MAC Address Filter Items (MAC addresses within a MAC Address Filter) without having to first navigate to and open a particular Zone, Network, or MAC Filter object. If you know exactly what you want to add and where you want to put it, this can save a lot of clicks.

The Toolbar panel is available in most screens of the Grid Manager interface, but displays different choices depending on navigational context (e.g. which tabs are selected at the top of the window).  If it is currently collapsed, click the gray toolbox icon to expand it.

User Profile

To open the User Profile dialog box, click the drop-down control labeled with your username in the upper right-hand corner of the interface, and select “Profile”.

• You can customize Table Size to increase the number of rows you see at a time in Grid Manager tables (up to 256).

  Be aware that increasing the table size may result in slower UI performance; you may wish to experiment with different values to find a good balance. The default is 20.

• You can enter an Email Address which Grid Manager will use e.g. to send you an email when one of your Scheduled Tasks completes.
• You can choose a Time Zone (e.g. “America/Chicago”) for displaying various time values in Grid Manager, including your own Last Login time at the upper-right corner of this User Profile dialog (reopen the dialog to see the effect of this setting).  The default is “Auto-detect time zone”, but in our experience that setting often ends up falling back to UTC.

Customizing Table Columns

Most tables in Grid Manager can be easily customized to display additional columns. For example, to add the Network Name column to the table that appears when browsing a list of Networks in DHCP View:

1. Mouse over any currently displayed column header (e.g. “Network”), and click the downward arrow button that appears on its right side.
2. Choose Columns > Edit Columns from the context menu.

   screenshot

   

3. Select the “Visible” checkbox for all desired columns (e.g. Network Name).
4. Click the “Apply” button.

Additional columns you may find useful:

• Network Name (when displaying a list of Networks in DHCP View or IPAM View)
• MAC Address (when displaying the contents of a Network or Range)
• Property Tag (when displaying the contents of a Network or MAC Address Filter)
• TTL (when displaying Records in a Zone)

Scheduled Tasks

If you don’t want your changes to take effect immediately, you can schedule them to occur later at a time of your choosing.  Important things to keep in mind:

• While a scheduled task is pending, no further changes can be made to the target object (by you or anyone else) until the task either completes or is cancelled.
• You can manage your own scheduled tasks, but you cannot manage scheduled tasks owned by another user.
• Always double check the Time Zone when choosing a time.
• When the IPAM appliance grid is upgraded to a new software release from the vendor, any Scheduled Tasks that have not completed before the upgrade begins will be automatically removed.  The service team will do our best to inform you when this occurs, but please avoid scheduling tasks many months or years in the future.

When adding a new object:

1. Use “Next” to keep advancing through the dialog screens until you reach a choice between “Now” and “Later” (or click “Schedule for Later” to skip ahead to this screen).
2. Choose “Later”, double-check the Time Zone, and enter the desired date and time.
3. When you click “Save & Close”, your change will be scheduled for the selected time.

When editing an existing object:

1. Click the blue calendar icon  at the top right-hand corner of the dialog window to show scheduling options.
2. Choose “Later”, double-check the Time Zone, and enter the desired date and time.
3. Optionally, you may collapse the scheduling options again (the calendar icon will turn green as a visual reminder).
4. When you click “Save & Close”, your change will be saved and scheduled for the time you selected.

When deleting an existing object:

1. Select the object in any table view (making sure no additional checkboxes are selected).
2. Click the drop-down arrow next to the Delete (trash can) icon above the table, and choose “Schedule Delete” from the context menu.
3. In the dialog box, choose “Delete Later”, double-check the Time Zone, enter the desired date and time, and click “Schedule Deletion”.

To manage your own scheduled tasks:

1. Navigate to Administration > Workflow > Task Manager using the rows of tabs at the top of the screen.
2. Your current scheduled tasks will be displayed with an Execution Status of “Pending”.
3. From here you can:
   • Mouse over the various fields for a pending task to show details of the change.
   • Optionally click “Toggle multi-line view” (above the table) to see more without using mouseover.  After you click it, the link text changes to “Toggle single-line view”.
   • Select a pending task and “Execute Now”.
   • Select a pending task and Reschedule it for a different time.
   • Select a pending task and Delete it.

Extensible Attributes

Grid Manager supports the definition of custom fields called Extensible Attributes to store additional data which is not natively part of an object type. Technology Services has created a few Extensible Attributes that you may find useful:

• Property Tag: Can be used to store a University property tag value for inventoried items
• Comment+: The built-in comment field for Grid Manager objects is limited to 256 characters. If you want to store additional comments, you can use this attribute to do so.

You can set these attributes on the Extensible Attributes subscreen, while creating a new object or editing an existing one:

1. Click the Add (+) icon above the Extensible Attributes table to place a new row in the table.
2. Click the Attribute Name field in that row to choose the desired attribute.
3. Click the Value field in that row and type the desired value.
4. Some extensible attributes (e.g. “Comment+”) can have multiple values for the same object; use the “+” icon to the left of the attribute name to add another value.

   screenshot

   

If you have a request for a new Extensible Attribute that is not already defined, please contact hostmgr.  Keep in mind that Extensible Attribute definitions are global, so they should be potentially relevant (or at the very least, not confusing) to the entire IT Pro community.

Recycle Bin

If you delete an item by accident, you may be able to restore it using the Recycle Bin.

To view items in your Recycle Bin:

1. Locate the Finder panel on the far left-hand side of the window; if it is currently collapsed, click the gray folder icon to expand it.
   
2. Expand the “Recycle Bin” subpanel.

   screenshot

   

3. To restore a deleted item, hover over the item in your list and click the “Restore” (circular arrow) icon.

   Grid Manager does not display a confirmation dialog before restoring an object from the Recycle Bin!

   It also does not show you the newly restored object; if you want to examine it, you must navigate to it on your own.

   You can also click “Show All” to display a table showing slightly more information about each deleted item (including the Parent/Container where it will be found if you choose to restore it).

CSV Import and Export

Most tables in Grid Manager have an Export (up arrow) button which you can use to download the contents of the table in CSV format.  This can be very helpful if you want to sort or filter your data in a way that the Grid Manager interface doesn’t support.

You can also import records into Grid Manager from a .csv file.

See CSV Imports and Exports for details.

Requesting Autoconfiguration Service

To enable autoconfiguration for your existing network, email net-trouble@illinois.edu with the following information:

• The name and IP CIDR of the network
• Which type of autoconfiguration you would like to enable (see below for details)
• If the network already has a DHCP server, let us know and provide details so that we can assist you in migrating your existing DHCP configuration into IPAM.
• Optionally, any other special configuration changes you require at this time (e.g. DHCP options set at the network level)

For new networks, work with your network designer to request autoconfiguration service as part of the network creation process.

Autoconfiguration Design Guide

There is no one-size-fits-all optimal approach to autoconfiguration; which type you choose, and which DHCP objects you configure in IPAM, will vary depending on how you want to use and administer your network.

The first step is to determine which of the following client behaviors you want to support:

• dynamic address allocation: each client automatically obtains an available IP address which is arbitrary and unpredictable. It doesn’t matter which client gets which IP, or if a particular client gets a different IP next time it comes back. This behavior is the easiest to configure, and requires very little administrative maintenance once set up.
• fixed address allocation: each client automatically obtains an IP address which has been administratively reserved for that client’s exclusive use.  This behavior requires more configuration work in IPAM (new clients must be added and old ones removed), but allows individual client IPs to be stable and predictable.
• manual client configuration: each client device is manually configured with the necessary network parameters, and does not use autoconfiguration at all. This is usually only necessary for devices which do not support autoconfiguration.

It is possible to mix and match, using different behaviors for different clients on the same network, but care must be taken to avoid conflicts!

Next, select the autoconfiguration type that best supports your desired behavior(s) – these are covered in detail in the following sections – and request that type of autoconfiguration service on your network.

Finally, if you’ve chosen DHCPv4 and/or IPv6 Stateful autoconfiguration, configure the desired DHCP objects in IPAM (see Using IPAM for detailed instructions):

• DHCP Ranges (Dynamic Pools) for dynamic address allocation
• DHCP-enabled Host Records and/or DHCP Fixed Addresses for fixed address allocation

  Notes for Microsoft DHCP users

  A Microsoft DHCP “Reservation” corresponds to a “Fixed Address” in IPAM. Avoid the temptation to create a “Reservation” in IPAM; that term refers to a different concept entirely and will not accomplish what you intend.

  Also, there is no need to place Fixed Addresses inside a DHCP Range (a “scope” in Microsoft terms); in fact, it’s best practice to avoid doing this. If you don’t want to use dynamic address allocation behavior on your network, you should not create a DHCP Range at all.

IPv4 Autoconfiguration Types

For IPv4, autoconfiguration is synonymous with DHCPv4, so the standard choices are simple; DHCPv4 is either enabled or disabled for any given network.

Notes:

• Several best practice recommendations are discussed in DHCP Ranges (Dynamic Pools).
• One strategy for preserving flexibility on a mixed-behavior net is to create a DHCP Range near the end of the net (i.e. highest-numbered IPs), and allocate Fixed Addresses, DHCP-enabled Hosts, and static IPs for manual configuration (if any) starting from the beginning of the net (lowest-numbered IPs).

IPv6 Autoconfiguration Types

For IPv6, there are multiple standard implementation choices for autoconfiguration, each supporting different behavior(s):

Notes:

• Where feasible, choose Stateless over Stateful autoconfiguration for your IPv6 networks.
  • Stateless is simpler than Stateful, and significantly easier on the DHCP servers.
  • If your network includes clients without DHCPv6 support, they will still be able to obtain an IPv6 address using Stateless autoconfiguration. Such clients will not learn the IPv6 DNS resolver address or other option values, but in many cases clients can function successfully without this information (e.g. by using IPv4 for DNS resolution, if available).
  • It is easy to migrate between Stateless and Stateful in the future if your requirements change.
• Most modern clients do support DHCPv6, as shown in https://en.wikipedia.org/wiki/Comparison_of_IPv6_support_in_operating_systems.

Limitations of DHCPv6 fixed address allocation

The DHCPv4 protocol specification (RFC 2131) includes a “client hardware address” (chaddr) field which in practice contains the MAC address of the requesting client’s network interface.  This makes it easy for a DHCPv4 server to identify clients by MAC, and to assign fixed address allocations based on the client’s MAC.

The DHCPv6 protocol specification (RFC 3315) does not include a client hardware address field; instead, it defines the DHCP Unique Identifier (DUID) which is intended as an opaque, globally unique, and stable identifier for the whole client device (not just for one of its network interfaces).  Because the MAC address is not included in DHCPv6 messages, there was originally no way for a DHCPv6 server to assign fixed address allocations based on the client’s MAC address; instead, you must configure them based on the client’s DUID.

The challenge is that it can be difficult or impossible to learn the client’s DUID ahead of time.  While the MAC address is a property of the physical hardware, the DUID (for most general-purpose computers, at least) is a software property generated and stored on disk by the operating system.  Depending on your operating system, the DUID may not even exist until it is needed for the first time – and it will almost certainly change if you reinstall the operating system, dual-boot to a second operating system, etc.

More recently, RFC 6939 provides a mechanism for the router (acting as relay agent) to provide the client’s MAC address so that DHCPv6 servers can use it to assign fixed address allocations.  However, as of this writing (April 2025) this option is not yet supported by most building routers on our campus.

Recommendations:

• Where possible, sidestep this issue entirely by using dynamic address allocation instead of fixed.
• If you do require fixed address allocation, make sure you understand the challenges discussed in this section and that you have a strategy for ascertaining client DUIDs.

Other Information

DHCP Standards details important guidelines and recommendations for using the DHCP service, as well as the default configuration parameters that will automatically apply to all networks unless you choose to override them.

Email Alerts explains the automated email notifications that may be sent to network administrators by the DHCP service.

Welcome! This space (go.illinois.edu/ipam) contains detailed technical documentation for IT Professionals regarding the IP Address Management (IPAM) service.

Information for everyday computer users is available at Networking, DNS Basics.

Use the sidebar on the right to navigate.

Quick links:

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Getting Started with IPAM

What’s New

See IPAM News Blog for the latest news regarding the IPAM service.  Use the “subscribe” link at the bottom if you would like to receive notifications of new posts.

Contact Us

General questions or support requests regarding the IPAM service should be directed to Illinois IPAM Hostmgr at hostmgr@illinois.edu (pronounced “host manager”).

Documentation Overview

DNS Standards provides general information and guidelines about the use of DNS on campus.

Requesting DNS Domains explains how to obtain a new domain.

DHCP Standards provides general information and guidelines about the use of DHCP on campus.

Requesting DHCP for Networks explains how to enable autoconfiguration for your network, and provides a conceptual overview of the different behaviors.

Using IPAM explains how to manage DNS and DHCP configuration for your existing networks and authoritative zones using IPAM Grid Manager.

Other Tools contains related information which may be helpful to IPAM users.

Known Issues describes known problems or limitations of IPAM which may be relevant to IT Professional customers.

Introduction

A traditional CNAME record (see also Stand-alone CNAME Records) defines a static, explicit alias in the DNS, with the oft-lamented technical limitation that a CNAME record cannot be placed at the apex of a zone (e.g. example.com).

Virtual Alias records are a non-standard but increasingly common DNS feature specifically designed to work around that limitation while still accomplishing a similar goal.

When we configure a virtual A Alias record in IPAM, our authoritative nameservers periodically query other nameservers to find the current A record(s) of the desired target name (e.g. abc123.cloudfront.net), and synthesize corresponding A record(s) for the alias name (e.g. example.com).  The result is a dynamic, transparent alias:

1. IPAM authoritative nameserver receives a query matching the virtual alias:  example.com. IN A?

2. IPAM authoritative nameserver sends a query for the target name: abc123.cloudfront.net. IN A?

3. IPAM authoritative nameserver receives this response for the target name:

   abc123.cloudfront.net. 60 IN A 198.51.100.17
   abc123.cloudfront.net. 60 IN A 198.51.100.18

4. IPAM authoritative nameserver returns this synthesized response for the virtual alias name:

   example.com. 60 IN A 198.51.100.17
   example.com. 60 IN A 198.51.100.18

The intermediate response is cached according to its TTL (time-to-live) value, so any further identical queries received by the same IPAM authoritative nameserver within the next 60s will skip steps 2 and 3, and return the same synthesized records with a lower remaining TTL.  Each individual IPAM authoritative nameserver maintains its own independent cache.

When the external nameserver’s response for the target name changes, IPAM’s response for the virtual alias name will also change (once the old response expires from cache).

If no A records are found for the target name, then IPAM will return zero A records for the virtual alias name.

This virtual A Alias record is only used to answer A record queries, but we could additionally and independently configure a virtual AAAA Alias record to answer AAAA record queries.

Key differences vs CNAME records

• A CNAME record affects query behavior for all record types, but each virtual Alias record applies to only one record type (e.g. only A records, or only AAAA records).  This enables virtual Alias records to coexist with records of other types, which is why they can be placed at a zone apex while a CNAME record cannot.

• Virtual Alias records are transparent (invisible) to clients, ultimately yielding the same query response as an equivalent set of static records:

  example.com.  IN A  198.51.100.17
  example.com.  IN A  198.51.100.18

  whereas CNAME records are explicitly returned and must be interpreted by the client:

  www.example.com.        IN CNAME  abc123.cloudfront.net.
  abc123.cloudfront.net.  IN A      198.51.100.17
  abc123.cloudfront.net.  IN A      198.51.100.18

  In this case only the CNAME record comes from our IPAM authoritative nameserver; the client’s recursive resolver combines that with A records from some other authoritative nameserver to form the sample response shown.

Limitations

Virtual Alias records cannot coexist in IPAM with other records of the same type (i.e. you cannot define both a virtual A Alias and a stand-alone A record for the same name).  There is no “fallback” functionality.

Virtual Alias records can be difficult to troubleshoot, since the external behavior of their target names might change unpredictably. 

Virtual Alias records cannot be used in DNSSEC signed zones.

At this time, we are offering virtual Alias records only for the zone apex of a second-level non-.edu domain (e.g. example.com), not for .edu subdomains.

(Note however that third-level .edu subdomains can be registered as a third-level CNAME record in the illinois.edu zone instead.)

Configuring virtual Alias records

Unfortunately we are not able to offer self-service configuration of virtual Alias records within IPAM at this time.  Changes should be made by request to hostmgr; be sure to include

• fully qualified domain name (FQDN) for the virtual alias
• which record type(s) should be aliased
• the target FQDN

Virtual Alias records vs DNS Traffic Control

Virtual Alias records and DNS Traffic Control both involve synthesized responses, but they are aimed at different use cases.

Consider using DNS Traffic Control if your service has a stable set of eligible target IP addresses, but some of them might be unhealthy from time to time.

Consider using a Virtual Alias record if your service has a stable target DNS name, but the set of IP addresses that name might resolve to is unpredictable (and it’s not possible to use a CNAME record).