Users Guide

2. When the passive system receives a control packet, it changes its session state to Init and sends a response to indicate
its state change. The response includes its session ID in the My Discriminator field and the session ID of the remote
system in the Your Discriminator field.
3. The active system receives the response from the passive system and changes its session state to Up. It then sends a
control packet to indicate this state change. Discriminator values exchange, and transmit intervals negotiate.
4. The passive system receives the control packet and changes its state to Up. Both systems agree that a session is
established. However, because both members must send a control packet, which requires a response, whenever there is
a state change or change in a session parameter, the passive system sends a final response indicating the state change.
After this, periodic control packets exchange.
BFD configuration
Before you configure BFD for a routing protocol, first enable BFD globally on both routers in the link. BFD is disabled by default.
● OS10 supports:
○ 64 BFD sessions at 100 minimum transmit and receive intervals with a multiplier of 4
○ 100 BFD sessions at 200 minimum transmit and receive intervals with a multiplier of 3
● OS10 does not support Demand mode, authentication, and Echo function.
● OS10 does not support BFD on multi-hop and virtual links.
● OS10 supports protocol liveness only for routing protocols.
● OS10 BFD supports only the BGP routing protocol. For IPv4 and IPv6 BGP, OS10 supports only the default virtual routing
and forwarding (VRF).
NOTE:
Dell EMC recommends that:
● For the S4100-ON series platform, you configure a BFD interval of 500 ms with multiplier of 3 or higher for
multidimensional scaled configurations.
● For other series switches, you configure a BFD interval of 200 ms with a multiplier of 4 or higher for multidimensional
scaled configurations.
552 Layer 3