Handling Shared Addresses
You can designate WhatsUp Gold Discovery address exceptions () for cases where Discovery detects devices on your network that share an identical network or hardware address. After you apply these exceptions and restart the Discovery Service, all devices using designated addresses under this exception will be visible via the Discovery Map and Discovery List.
Background
By default, WhatsUp Gold Discovery uses network or hardware addressing to identify the 'uniqueness' of devices. Shared addressing can occur in special architectures, normally restricted to LANs, such as high-availability environments, network load balancing, and virtualization schemes. In these scenarios, IP addresses or MAC addresses can be unreliable predictors of device or host boundaries.
Actions
. 
Create new IP address exception. Subnet ranges supported.
- . Add/Edit an address or address range. You can specify subnets by using CIDR notation. Reserved IP addresses cannot be edited.
- . You can use this field to explain the policy or scenario behind the exception.
IP Address Examples
Use Classless Inter-domain Routing notation (CIDR) to specify all IPs for a given subnet. For example, to specify all IPs for a given switch or controller, use CIDR notation to specify the network part of the address. For example, to exclude 198.51.100.1 to 198.51.100.254 here are the syntax and string values.
Designate a subnet. Create address exceptions for a single subnet.
Use CIDR notation to designate address exception behavior for an entire subnet.
Syntax:
<IP-address>/<bits-to-consider-as-network-part>
Example:
198.51.100.0/24
--where "/24" denotes the first 3 octets are the network part of this address (198.51.100).
--and, where all hosts beneath the network part will exhibit address exception behavior in WhatsUp Gold.
The previous value is a more compact version of:
198.51.100.1-198.51.100.254
Designate a domain. Create exceptions for an entire network.
You can also use CIDR notation to add address exceptions across a typical corporate network or domain. 'Wide net' exceptions like this can be deployed when your WhatsUp Gold monitoring solution is discovered and in place, and as part of a discovery sweep that detects new devices or outliers.
Syntax:
<IP-address>/<bits-to-consider-as-network-part>
Example:
198.168.0.0/16
--where "/16" denotes the first 2 octets are the network part of this address (198.168).
--and, where all devices with IPs 'beneath' the network part will exhibit address exception behavior in WhatsUp Gold.
. Create new MAC address exception. Prefix matching supported.
- . Add/Edit an address or prefix.
- . You can use this field to explain the policy or scenario behind the exception.
MAC Address Example
Single MAC address. Simplest case.
MAC Address Example
Specify a single MAC
00-00-5E-00-53-88
Specify MAC by Vendor Prefix
- Add exception for MACs VNIC IDs generated by VMware:
00:50:56
- Include MACs reserved by ICANN, IANA for testing and documentation.
00-00-5E
- Include a set of MACs used by Dell.
EC.F4.BB
Designate by Vendor Prefix. Watch for duplicates over a range.
Specify MAC by Vendor Prefix
- Add exception for MACs VNIC IDs generated by VMware:
00:50:56
- Include MACs reserved by ICANN, IANA for testing and documentation.
00-00-5E
- Include a set of MACs used by Dell.
EC.F4.BB
. 
Modify exception. Built-in exceptions (IANA/IETF reserved/restricted addresses, for example) cannot be modified.
- . Add/Edit an address or address range. You can specify subnets by using CIDR notation. Reserved IP addresses cannot be edited.
- . You can use this field to explain the policy or scenario behind the exception.
IP Address Examples
Use Classless Inter-domain Routing notation (CIDR) to specify all IPs for a given subnet. For example, to specify all IPs for a given switch or controller, use CIDR notation to specify the network part of the address. For example, to exclude 198.51.100.1 to 198.51.100.254 here are the syntax and string values.
Designate a subnet. Create address exceptions for a single subnet.
Use CIDR notation to designate address exception behavior for an entire subnet.
Syntax:
<IP-address>/<bits-to-consider-as-network-part>
Example:
198.51.100.0/24
--where "/24" denotes the first 3 octets are the network part of this address (198.51.100).
--and, where all hosts beneath the network part will exhibit address exception behavior in WhatsUp Gold.
The previous value is a more compact version of:
198.51.100.1-198.51.100.254
Designate a domain. Create exceptions for an entire network.
You can also use CIDR notation to add address exceptions across a typical corporate network or domain. 'Wide net' exceptions like this can be deployed when your WhatsUp Gold monitoring solution is discovered and in place, and as part of a discovery sweep that detects new devices or outliers.
Syntax:
<IP-address>/<bits-to-consider-as-network-part>
Example:
198.168.0.0/16
--where "/16" denotes the first 2 octets are the network part of this address (198.168).
--and, where all devices with IPs 'beneath' the network part will exhibit address exception behavior in WhatsUp Gold.
. 
Delete exception.
Allows network or hardware addressing to be used authoritatively to identify a device.
: Before you Delete an IP address exception, copy the IP address value. You can re-use this value, including CIDR notation, if applicable, for the Discovery Scan.
Typical Workflow When Manging Devices Using Duplicate Addressing
A typical workflow for managing and monitoring devices using shared addressing scheme is:
1.
|
Identify
|
Identify addresses or segments you need to apply exceptions to. For more information, see the topic Typical Uses of Shared Addressing.
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2.
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Start Fresh
|
If you already scanned your network, it is best practice to start fresh —delete any devices from WhatsUp Gold that might have been merged due to shared addressing schemes.
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3.
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Add Exception
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Apply exceptions for these addresses either individually, as a subnet range, or vendor prefix (MAC).
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4.
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Restart and Rescan
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Restart the discovery service to make your exceptions active and re-run discovery.
After you apply your address exceptions, and after the Discovery service is restarted and re-reads its configuration, you will need to rescan the network, network segment, or address of interest to see the results of your changes.
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5.
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Add Monitoring
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After you have scanned your network, you can determine if any new devices found based on address exception rules should be added to the monitored network and count against your licensing.
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: To apply address exceptions to the WhatsUp Gold Discovery configuration, you need to restart the Discovery service.
Rescan Guidelines
Use these scan/rescan guidelines after making changes to the table of IP address exceptions:
- Scan the same IP range. If you suspect shared address use is limited to a specific subnet or range, re-Discover the range you added an address exception for. For example, this is the best approach if you are looking for duplicates between address pools allocated by one-or-more wireless controllers, ranges that you know where VMs can be typically found, or any of the other scenarios where IP duplication is likely to occur.
- Apply scan to all monitored devices. If you want to apply changes only to monitored devices, select all devices from the Network List, and choose
from the management actions menu.
Rescan guidelines for MAC address exceptions:
- Scan specific subnets or IP ranges. For example, if you added an exception for the VMware vendor MAC prefix (00:50:56), you can target a rescan on the subnet or IP address range where you know VMware VMs are running.
- Sweep the network. If you are taking a 'cast-a-wide-net' approach, and you are just looking for a misconfigured, masquerading, or other unexpected use of addressing, you can widen scan coverage.