Link Aggregation Protocols: LACP & PAgP

Link Aggregation - LACP and PAgP

• Link Aggregation Control Protocol (LACP) is an open standard defined by IEEE 802.3ad. It combines multiple physical Ethernet links into a single logical link.
• LACP uses LACP Data Units (LACPDUs) to negotiate which links will be active.
• PAgP (Port Aggregation Protocol) is a Cisco proprietary protocol that automatically negotiates EtherChannel formation between Cisco devices.
• PAgP uses PAgP packets to manage EtherChannel, similar to LACP.
• LACP Modes:
  • Active Mode: Port actively sends LACP packets to form an EtherChannel.
  • Passive Mode: Port forms an EtherChannel only upon receiving LACP packets from a device in active mode.
• PAgP Modes:
  • Desirable Mode: Port actively sends PAgP packets to negotiate an EtherChannel.
  • Auto Mode: Port forms an EtherChannel only when receiving PAgP packets from a port in desirable mode.

Configuring Link Aggregation on Switches

• Step 1: Choose interfaces for aggregation: Select physical interfaces (e.g., FastEthernet or GigabitEthernet ports).
• Step 2: Create EtherChannel group: Assign selected interfaces to a channel group using LACP or PAgP protocols.
• Step 3: Set port-channel interface: Configure the logical port-channel interface as either trunk or access, depending on network requirements.
• Step 4: Verify configuration: Use commands like show etherchannel summary or show port-channel to confirm the EtherChannel's functionality.

VLAN Membership

• VLAN Membership: Defines how devices are assigned to VLANs.
• Static VLAN Membership:
  • Devices are manually assigned to a VLAN by configuring their connected switch port.
  • Also known as port-based VLAN configuration.
• Static VLAN Advantages:
  • Simple configuration for small networks.
  • High control over VLAN assignments.
• Static VLAN Disadvantages:
  • Not scalable for large networks.
  • Requires manual configuration if devices change locations.
• Dynamic VLAN Membership:
  • VLAN assignments are determined automatically based on device's MAC address.
  • Requires a VLAN Management Policy Server (VMPS).
• Dynamic VLAN Advantages:
  • Ideal for environments with frequent device movement.
  • Reduces manual configuration.
• Dynamic VLAN Disadvantages:
  • More complex setup than static VLANs.
  • Requires a VMPS server, adding cost and complexity.

VLAN Management

• VLAN Management: Configuring, monitoring, and maintaining VLANs.
• VLAN Naming and Documentation:
  • Each VLAN should have a clear, descriptive name.
  • Document VLAN configuration, including VLAN IDs, names, associated ports, dynamic policies.
• VLAN Trunking and Management Across Switches:
  • Trunk Links: Allow traffic from multiple VLANs to pass between switches using 802.1Q VLAN tagging.
  • VLAN configurations must be consistent across switches using protocols like VTP (VLAN Trunking Protocol) for management across the entire network.

VTP Configuration

• Configure Switch 1 as VTP Server:

  • Set switch to VTP Server mode (default, but set explicitly).
  • Set VTP domain name.
  • Set optional VTP password.
  • Create VLANs on the server.
  • Configure the trunk link on the interface connecting to the client switch.

• Configure Switch 2 as VTP Client:

  • Set switch to VTP Client mode.
  • Set the same VTP domain name as the Server.
  • Set the same VTP password as the Server.
  • Configure the trunk link on the interface connecting to the Server switch.

• Verify VTP Configuration:

  • On the client switch, check if the VLANs created on the server have been propagated.
  • Use commands like show vlan brief, show vtp status to verify VTP status on both switches.

Dynamic Routing

• Routing: Enables communication between networks, ensuring data reaches the correct destination.
• Router: Forwards data packets between networks.
• Routing Table: Stores routes to network destinations.
• Static Routing:
  • Routes are manually configured by the network administrator.
  • The router follows a predefined path for forwarding packets.
• Static Routing Advantages:
  • Simple for small networks.
  • Full control over data paths.
• Static Routing Disadvantages:
  • Time-consuming for large networks.
  • Lack of adaptability to network changes.
• Dynamic Routing:
  • Routers automatically learn and adjust to network changes using routing protocols.
• Dynamic Routing Advantages:
  • Adapts to network changes (e.g., link failures).
  • Scalable for large networks.
• Dynamic Routing Disadvantages:
  • More complex than static routing.
  • Requires processing and network resources.

Overview of Routing Protocols

• RIP (Routing Information Protocol):
  • Distance-vector protocol.
  • Metric: Hop count (maximum of 15 hops).
  • Features: Simple configuration, less efficient for large networks due to hop count limitation.
  • Versions: RIP v1 (classful), RIP v2 (classless, supports subnet masks).
• OSPF (Open Shortest Path First):
  • Link-state protocol.
  • Metric: Cost, based on bandwidth.
  • Features: Efficient for larger networks, provides fast convergence.

This quiz covers the fundamentals of Link Aggregation Control Protocol (LACP) and Port Aggregation Protocol (PAgP), including their definitions, modes of operation, and configuration. Test your knowledge on how these protocols combine multiple Ethernet links into a single logical connection and their specific functionalities related to Cisco devices.