# Specifying a local IP interface as a candidate RP

Because PIM-SM cannot run without an RP, you must specify at least one C-RP in the domain.

With the Ethernet Routing Switch 5000 Series, you can configure only one local interface as a C-RP for any number of groups.

Using the GroupMask value, you can configure a C-RP for several groups in one configuration. For example, with a C-RP configuration with a GroupAddress value of 224.0.0.0 and a GroupMask of 240.0.0.0, you can configure the C-RP for a multicast range from 224.0.0.0 to 239.255.255.255.

Use the following procedure to configure a local PIM-SM interface as a candidate RP (C-RP).

## Variable definitions

The following table describes the fields of the Insert Candidate RP dialog box.

Field | Description
--- | ---
GroupAddress | Specifies the IP address of the multicast group. Together with the group mask, the group address identifies the prefix that the local router uses to advertise itself as a C-RP.
GroupMask | Specifies the address mask of the multicast group. Together with the group address, the group mask identifies the prefix that the local router uses to advertise itself as a C-RP.
RPAddress | Specifies the IP address of the C-RP. This address must be one of the local PIM-SM enabled interfaces.

## Procedure steps

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

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

3. In the work area, click the Candidate RP tab.

4. In the toolbar, click Insert.

   The Insert Candidate RP dialog box appears.

5. In the GroupAddress box, enter the multicast group address.

6. In the GroupMask box, enter the multicast group mask.

7. In the RPAddress box, enter the address of the C-RP.

8. Click Insert.