BFD Sessions
BFD must be enabled on both sides of a link in order to establish a session.
The two participating systems can assume either of two roles:
Active
The active system initiates the BFD session. Both systems can be active for the
same session.
Passive
The passive system does not initiate a session. It only responds to a request for
session initialization from the active system.
A BFD session has two modes:
Asynchronous
mode
In Asynchronous mode, both systems send periodic control messages at an agreed
upon interval to indicate that their session status is Up.’
Demand mode
If one system requests Demand mode, the other system stops sending periodic
control packets; it only sends a response to status inquiries from the Demand
mode initiator. Either system (but not both) can request Demand mode at any time.
NOTE: Dell Networking OS supports Asynchronous mode only.
A session can have four states: Administratively Down, Down, Init, and Up.
Administratively
Down
The local system does not participate in a particular session.
Down
The remote system is not sending control packets or at least not within the
detection time for a particular session.
Init
The local system is communicating.
Up
Both systems are exchanging control packets.
The session is declared down if:
• A control packet is not received within the detection time.
• Sufficient echo packets are lost.
• Demand mode is active and a control packet is not received in response to a poll packet.
BFD Three-Way Handshake
A three-way handshake must take place between the systems that participate in the BFD session.
The handshake shown in the following illustration assumes that there is one active and one passive
system, and that this session is the first session established on this link. The default session state on both
ports is Down.
1.
The active system sends a steady stream of control packets that indicates that its session state is
Down, until the passive system responds. These packets are sent at the desired transmit interval of
the Active system. The Your Discriminator field is set to zero.
2.
When the passive system receives any of these control packets, it changes its session state to Init
and sends a response that indicates 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.
Bidirectional Forwarding Detection (BFD)
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Содержание S4820T
Страница 1: ...Dell Configuration Guide for the S4820T System 9 8 0 0 ...
Страница 282: ...Dell 282 Control Plane Policing CoPP ...
Страница 569: ...Figure 62 Inspecting Configuration of LAG 10 on ALPHA Link Aggregation Control Protocol LACP 569 ...
Страница 572: ...Figure 64 Inspecting a LAG Port on BRAVO Using the show interface Command 572 Link Aggregation Control Protocol LACP ...
Страница 573: ...Figure 65 Inspecting LAG 10 Using the show interfaces port channel Command Link Aggregation Control Protocol LACP 573 ...
Страница 617: ...mac address table static multicast mac address vlan vlan id output range interface Microsoft Network Load Balancing 617 ...
Страница 622: ...Figure 81 Configuring Interfaces for MSDP 622 Multicast Source Discovery Protocol MSDP ...
Страница 623: ...Figure 82 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 623 ...
Страница 624: ...Figure 83 Configuring PIM in Multiple Routing Domains 624 Multicast Source Discovery Protocol MSDP ...
Страница 629: ...Figure 86 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 629 ...
Страница 630: ...Figure 87 MSDP Default Peer Scenario 3 630 Multicast Source Discovery Protocol MSDP ...
Страница 751: ...10 11 5 2 00 00 05 00 02 04 Member Ports Te 1 2 1 PIM Source Specific Mode PIM SSM 751 ...
Страница 905: ...Figure 112 Single and Double Tag First byte TPID Match Service Provider Bridging 905 ...
Страница 979: ...6 Member not present 7 Member not present Stacking 979 ...
Страница 981: ...storm control Storm Control 981 ...
Страница 999: ... Te 1 1 0 INCON Root Rootguard Te 1 2 0 LIS Loopguard Te 1 3 0 EDS Shut Bpduguard Spanning Tree Protocol STP 999 ...
Страница 1103: ...Figure 134 Setup OSPF and Static Routes Virtual Routing and Forwarding VRF 1103 ...