# Displaying external link state database information

Use the following procedure to view the OSPF external link state database.

## Prerequisites

- Install the Advanced License.

- Enable IP routing globally on the switch.

- Assign an IP address to the VLAN that you want to enable with OSPF.

  Routing is automatically enabled on the VLAN when you assign an IP address to it.

## Procedure steps

1. From the navigation tree, double-click IP Routing.

2. In the IP Routing tree, double-click OSPF.

3. In the work area, click the Ext. Link State Database tab.

4. In the toolbar, click Refresh to update the displayed information.

## Variable definitions

The following table describes the fields of the Ext. Link State Database tab.

Field | Description
--- | ---
Type | Specifies the type of link state advertisement. Each link state type has a separate advertisement format.
Lsid | Specifies the Link State ID, a link state type-specific field containing either a Router ID or an IP address. This field identifies the section of the routing domain that is being described by the advertisement.
RouterId | Specifies the unique identifier of the originating router in the Autonomous System.
Sequence | Detects old or duplicate link state advertisements by assigning an incremental number to duplicate advertisements. The higher the sequence number, the more recent the advertisement.
Age | Specifies the age of the link state advertisement in seconds.
Checksum | Specifies the checksum of the complete content of the advertisement, excluding the Age field. This field is excluded so that the advertisement's age can be increased without updating the checksum. The checksum used is the same as that used in ISO connectionless datagrams and is commonly referred to as the Fletcher checksum.
Advertisement | Specifies the hexadecimal representation of the entire link state advertisement including the header.