Table of Contents
1. Introduction
2. Understanding Frame-Relay Multi-Point Configuration with Sub-Interface
3. Configuration Steps
Step 1: Selecting the Main Interface
Step 2: Disabling IP Address on the Main Interface
Step 3: Setting Encapsulation
Step 4: Configuring LMI Type
Step 5: Creating the Multi-Point Sub-Interface
Step 6: Assigning IP Address to the Sub-Interface
Step 7: Mapping IP Addresses to DLCIs
4. Sample Configuration
5. Additional Features
6. Best Practices
7. Verification Commands
8. Conclusion
1. Introduction
Frame-Relay is a cost-effective WAN protocol used for connecting multiple remote sites to a central hub. This guide provides a comprehensive walkthrough for configuring Frame-Relay Multi-Point using sub-interfaces.
2. Understanding Frame-Relay Multi-Point Configuration with Sub-Interface
A Multi-Point Frame-Relay configuration with sub-interfaces allows a single physical interface to handle multiple virtual circuits (DLCIs), each representing a unique connection to remote sites.
3. Configuration Steps
Step 1: Selecting the Main Interface
First, select the appropriate serial interface on the router.
R1(config)# interface serial 0/0/0
Step 2: Disabling IP Address on the Main Interface
Remove any IP address configuration from the main interface to prepare it for sub-interface configuration.
R1(config-if)# no ip address
Step 3: Setting Encapsulation
Set the encapsulation type to Frame-Relay. This is done on the main interface, not the sub-interface.
R1(config-if)# encapsulation frame-relay
Step 4: Configuring LMI Type
Configure the Local Management Interface (LMI) type. The default is 'cisco', but 'ansi' or 'q933a' can also be specified.
R1(config-if)# frame-relay lmi-type [ansi, q933a, cisco]
Step 5: Creating the Multi-Point Sub-Interface
Create a sub-interface with a custom number, typically matching the DLCI number for clarity.
R1(config-if)# interface serial 0/0/0.752 multipoint
Step 6: Assigning IP Address to the Sub-Interface
Assign an IP address to the sub-interface. A subnet larger than /30 is typically used for Multi-Point configurations.
R1(config-subif)# ip address 192.168.5.1 255.255.255.248
Step 7: Mapping IP Addresses to DLCIs
Map the local and remote IP addresses to their respective DLCIs. The 'broadcast' keyword allows broadcast and multicast traffic. Specify 'ietf' if using IETF encapsulation.
R1(config-subif)# frame-relay map ip 192.168.5.1 752
R1(config-subif)# frame-relay map ip 192.168.5.2 752 broadcast [ietf, cisco]
R1(config-subif)# frame-relay map ip 192.168.5.3 339 broadcast [ietf, cisco]
4. Sample Configuration
Below is the complete configuration example for Router R1 with a Multi-Point Frame-Relay connection using sub-interfaces:
R1(config)# interface serial 0/0/0
R1(config-if)# no ip address
R1(config-if)# encapsulation frame-relay
R1(config-if)# frame-relay lmi-type ansi
R1(config-if)# interface serial 0/0/0.752 multipoint
R1(config-subif)# ip address 192.168.5.1 255.255.255.248
R1(config-subif)# frame-relay map ip 192.168.5.1 752
R1(config-subif)# frame-relay map ip 192.168.5.2 752 broadcast ietf
R1(config-subif)# frame-relay map ip 192.168.5.3 339 broadcast ietf
In this example:
- interface serial 0/0/0: Specifies the main serial interface.
- no ip address: Removes any IP address from the main interface.
- encapsulation frame-relay: Sets Frame-Relay encapsulation on the main interface.
- frame-relay lmi-type ansi: Configures the LMI type to ANSI.
- interface serial 0/0/0.752 multipoint: Creates a multi-point sub-interface.
- ip address 192.168.5.1 255.255.255.248: Assigns an IP address to the sub-interface.
- frame-relay map ip 192.168.5.1 752: Maps the local IP address to DLCI 752.
- frame-relay map ip 192.168.5.2 752 broadcast ietf: Maps the remote IP address 192.168.5.2 to DLCI 752 with broadcast and IETF encapsulation.
- frame-relay map ip 192.168.5.3 339 broadcast ietf: Maps the remote IP address 192.168.5.3 to DLCI 339 with broadcast and IETF encapsulation.
5. Additional Features
- Traffic Shaping: Implement traffic shaping to manage bandwidth and ensure Quality of Service (QoS).
- Inverse ARP: Utilize Inverse ARP to automatically map remote IP addresses to local DLCIs, simplifying the configuration.
6. Best Practices
- Consistent Configuration: Ensure consistency across all router configurations to avoid connectivity issues.
- Monitor LMI: Regularly monitor the LMI status to ensure the health of the Frame-Relay network.
- Secure Frame-Relay Links: Use access control lists (ACLs) and other security measures to protect Frame-Relay links from unauthorized access.
- Documentation: Maintain detailed documentation of Frame-Relay configurations for troubleshooting and maintenance.
7. Verification Commands
- Static: Map entry was created through a frame-relay map statement.
- Dynamic: Map entry was created through Inverse ARP.
- Active: PVC is fully connected and functional.
- Inactive: Connected to Frame-Relay switch, but the other side isn’t seen.
- Delete: Not talking to the Frame-Relay switch.
