Bfd Session Modes And Operating Modes; Supported Features - HPE FlexFabric 5700 Series Configuration Manual

BFD session modes and operating modes

BFD sessions use the following types of packets:
•
Echo packets—Encapsulated into UDP packets with port number 3785.
•
Control packets—Encapsulated into UDP packets with port number 3784 for single-hop
detection or port number 4784 for multihop detection.
Echo packet mode
The local end of the link sends echo packets to establish BFD sessions and monitor link status. The
peer end does not establish BFD sessions and only forwards the packets back to the originating end.
In echo packet mode, BFD supports only single-hop detection and the BFD session is independent
of the operating mode.
Control packet mode
Both ends of the link exchange BFD control packets to monitor link status.
Before a BFD session is established, BFD has two operating modes—active and passive.
•
Active mode—BFD actively sends BFD control packets regardless of whether any BFD control
packet is received from the peer.
•
Passive mode—BFD does not send control packets until a BFD control packet is received from
the peer.
At least one end must operate in active mode for a BFD session to be established.
After a BFD session is established, the two ends can operate in the following BFD operating modes:
•
Asynchronous mode—The device periodically sends BFD control packets. The device
considers that the session is down if it does not receive any BFD control packets within a
specific interval.
•
Demand mode—The device periodically sends BFD control packets. If the peer end is
operating in Asynchronous mode (default), the peer end stops sending BFD control packets. If
the peer end is operating in Demand mode, both ends stop sending BFD control packets. When
the connectivity to another system needs to be verified explicitly, a system sends several BFD
control packets that have the Poll (P) bit set at the negotiated transmit interval. If no response is
received within the detection interval, the session is considered down. If the connectivity is
found to be up, no more BFD control packets are sent until the next command is issued.
In addition, both ends of the link can exchange BFD control packets to establish and maintain BFD
sessions, and one end of the link sends echo packets to monitor link status.

Supported features

•
Static routing. For more information, see Layer 3—IP Routing Configuration Guide.
•
IPv6 static routing. For more information, see Layer 3—IP Routing Configuration Guide.
•
RIP. For more information, see Layer 3—IP Routing Configuration Guide.
•
OSPF. For more information, see Layer 3—IP Routing Configuration Guide.
•
OSPFv3. For more information, see Layer 3—IP Routing Configuration Guide.
•
IS-IS. For more information, see Layer 3—IP Routing Configuration Guide.
•
IPv6 IS-IS. For more information, see Layer 3—IP Routing Configuration Guide.
•
BGP. For more information, see Layer 3—IP Routing Configuration Guide.
•
IPv6 BGP. For more information, see Layer 3—IP Routing Configuration Guide.
•
PIM. For more information, see IP Multicast Configuration Guide.
•
IPv6 PIM. For more information, see IP Multicast Configuration Guide.
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