LACP vs PAGP: What’s the Difference?

LACP: LACP is a layer 2 protocol it is also known as IEEE 802.3ad link aggregation control protocol; LACP is an open standard protocol used for ethernet link aggregation. This helps in dynamically building an EtherChannel. It is supported in the transparent mode in Layer 2 in addition to current support in Layer 3 mode for 5000 series SRX devices. When these devices use link aggregation control protocol to clump the member links, generating fat pipes, with peer devices. Bandwidth can be improved by adding member links. Improved bandwidth is significant, especially for Reth and AE interfaces, for sending and receiving packets between the peer and for the whole system.
Link aggregation control protocol also offers automatic configuration, monitoring member links, and automatic determination. LACP is compatible with other devices that run the 802.3ad protocol. It automatically hobbles the member links without physically configuring the LAG, and thus avoiding errors.

LACP has two states or modes, i.e., Active Mode and Passive Mode.

1. Active Mode or Active State –
   In this mode, ports are placed in an active negotiating state that is negotiation with other ports is initiated by exchanging LACP packets.
2. Passive Mode or Active State –
   In this mode, the ports are placed in passive negotiating states, i.e., ports reply to the received LACP packets but it doesn’t initiate LACP.

PAGP: PAGP is a cisco-proprietary protocol also known as aggregation protocol; It allows the creation of EthernetChannel automatically by exchanging PAGP packets between ports. PAGP allows the switches to learn the identity of its associates’ apt of supporting PAGP and then it dynamically divides the similarly configured ports into a single logical channel or aggregate port. It is also utilized in running the Cisco VSS, which consists of two 6500 series physical catalyst switches acting as a single logical switch. 

PAGP has two states or modes, i.e., Auto and Desirable.

1. Auto Mode –
   In auto mode, all the interfaces are put in a passive negotiating state, that is, these interfaces reply to the received port aggregation packets though it does not instigate PAGP negotiation.
2. Desirable Mode –
   In desirable mode, the interfaces are placed in an active negotiating state, that is the negotiation with other interfaces is instigated by sending port aggregation packets.

Difference between LACP and PAGP: