R3721-F3210-F3171-HP High-End Firewalls High Availability Configuration Guide-6PW101

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echo packets have a similar format as BFD control packets (except that the Desired Min TX Interval and

Required Min RX Interval fields are null) with UDP port number 3785. Figure 76 i

llustrates the packet

format.

Figure 76 BFD packet format

• Vers—Protocol version. The protocol version is 1.

• Diag—This bit indicates the reason for the last transition of the local session from up to some other

state. Table 18 lists

the states.

Table 18 Diag bit values

Dia

Descri

tion

0 No Diagnostic

1 Control Detection Time Expired

2 Echo Function Failed

3 Neighbor Signaled Session Down

4 Forwarding Plane Reset

5 Path Down

6 Concatenated Path Down

7 Administratively Down

8 Reverse Concatenated Path Down

9~31 Reserved for future use

• State (Sta)—Current BFD session state. Its value can be 0 for AdminDown, 1 for Down, 2 for Init,

and 3 for Up.

• Poll (P)—If set, the transmitting system is requesting verification of connectivity, or of a parameter

change. If clear, the transmitting system is not requesting verification.

• Final (F)—If set, the transmitting system is responding to a received BFD control packet that had the

Poll (P) bit set. If clear, the transmitting system is not responding to a Poll.

• Control Plane Independent(C)—If set, the transmitting system's BFD implementation does not share

fate with its control plane (BFD is implemented in the forwarding plane and can continue to function

through disruptions in the control plane.) If clear, the transmitting system's BFD implementation

shares fate with its control plane.

• Authentication Present (A)—If set, the Authentication Section is present and the session is to be

authenticated.