Adjusting Control Parameters for Establishing Neighbor Relationships
Pre-configuration Tasks
Before configuring control parameters for establishing neighbor relationships, complete the following tasks:
- Configure a unicast routing protocol to ensure normal unicast routing on the network.
- Enable PIM-SM.
Adjusting Control Parameters for Hello Messages
Context
PIM devices send Hello messages periodically to maintain PIM neighbor relationships. When a PIM device receives a Hello message from a neighbor, the PIM device starts the timer and sets the timer to the holdtime of Hello messages. If the PIM device does not receive a new Hello message from the neighbor within the holdtime, it considers the neighbor invalid or unreachable. Therefore, the interval for a PIM device to send Hello messages must be smaller than the holdtime of Hello messages.
If multiple PIM devices transmit Hello messages simultaneously, a conflict occurs on the network. To solve this problem, when a PIM device receives a Hello message, it waits a period before transmitting the Hello message. This period can be a random value and is smaller than the maximum delay for triggering Hello messages.
The interval for sending Hello messages and the holdtime of Hello messages can be set in either the global PIM view or interface view. If you configure the two parameters in the global PIM view and in the interface view simultaneously, the configuration in the interface view takes effect.
You can configure the maximum delay for triggering Hello messages only in the interface view.
Enabling Downstream Neighbor Tracking
Context
When sending a Hello message, a PIM device generates a Generation ID and adds it to the message. If the status of the device changes, the device generates a new Generation ID. When a neighboring device receives the Hello message and finds that the Generation ID changes, it sends a Join message to refresh the neighbor relationship. Devices on a shared network segment use a listening mechanism to prevent multiple devices from simultaneously sending Join messages to the same upstream device. When a device detects the Join message sent from another device to an upstream device, it does not send Join messages to this upstream PIM device. Therefore, the upstream PIM neighbor with a changed Generation ID cannot refresh neighbor relationships with each downstream neighbor.
After the neighbor tracking function is enabled, PIM devices no longer trigger Join message suppression when they detect a Join message sent by another PIM device. Instead, they keep sending Join messages to the same upstream neighbor.
The neighbor tracking function can be enabled globally or on an interface. If you configure the neighbor tracking function in the global PIM view and in the interface view simultaneously, the configuration in the interface view takes effect.
The neighbor tracking function can be implemented only when all devices on the shared network segment have this function enabled.
Configuring PIM Neighbor Filtering
Context
- Configure a valid neighbor address range to prevent unauthorized neighbors from connecting to the network.
- Configure the router to reject Hello messages without Generation IDs so that router connects to normally working PIM neighbors.
- Enable the PIM neighbor check function to discard Join/Prune messages and Assert messages that are not sent from neighbors or send Join/Prune messages and Assert messages only to neighbors.
Procedure
- Run system-view
The system view is displayed.
- Run interface interface-type interface-number
The interface view is displayed.
- Run pim neighbor-policy { basic-acl-number | acl-name acl-name }
The range of valid neighbor addresses is configured.
If the IP address of a PIM neighbor that has established a neighbor relationship with the router is not in the configured range of valid neighbor addresses, the router will no longer receive Hello messages from this PIM neighbor. When the holdtime of Hello messages expires, the neighbor relationship between the PIM device and the router is terminated.
- Run pim require-genid
The device is configured to receive only Hello messages that contain Generation IDs.
- Run quit
The system exits from the interface view.
- Run pim [ vpn-instance vpn-instance-name ]
The PIM view is displayed.
- Run neighbor-check { receive | send }
The PIM neighbor check function is enabled.
Verifying the Configuration of Control Parameters for Establishing Neighbor Relationships
Prerequisites
After the control parameters for establishing the neighbor relationship are adjusted, you can check information about the PIM interface and the PIM neighbor.
Procedure
- Run the display pim [ vpn-instance vpn-instance-name | all-instance ] interface [ interface-type interface-number | up | down ] [ verbose ] command to check PIM information on an interface.
- Run the display pim [ vpn-instance vpn-instance-name | all-instance ] neighbor [ neighbor-address | interface interface-type interface-number | verbose ] * command to check information about PIM neighbors.