BFD는 Bidirectional Forwarding Direction은 Transport Node(Host 또는 Edge)의 TEP Interface, BGP Peer 간의 Forwarding Path Failure를 감지하기 위해서 사용됩니다.
BFD는 RFC5880에 정의되어 있습니다.
https://datatracker.ietf.org/doc/rfc5880/
BFD는 상태 확인을 위해서, BFD Control 이라는 Heartbeat과 유사한 Packet(UDP 3784)을 이용합니다.
또한, Transport Node(Host 또는 Edge)간의 TEP Interface간에 주고받는 BFD Packet는 VNI 0 값을 이용하여 GENEVE로 Encapsulation 되게 됩니다.
TEP Tunnel Interface 간에는 매 초마다 Packet을 보내며, 3초 동안 반대편으로 부터 수신되는 BFD Packet이 없는 경우 Down 상태로 변경됩니다.
BFD의 상태 정보는 BFD Control Packet 내에서 State field 값으로 Down, Init, Up으로 구분되며 상태가 변경된 상세 정보를 제공하기 위한 Diagnostic field도 존재합니다.
BFD State
| State (Sta) The current BFD session state as seen by the transmitting system. Values are: 0 -- AdminDown 1 -- Down 2 -- Init 3 -- Up |
Down State는 양 방향의 Path에 문제가 있는 경우,
한 쪽이 Init State이고, 다른 한 쪽이 Down State인 경우, Init State 쪽 Interface는 반대편으로부터 BFD Packet을 정상적으로 수신하고 있다는 의미
Up State는 양 방향으로 BFD Packet을 주고받는데 문제가 없다는 의미
BFD Diagnotic
| Diagnostic (Diag) A diagnostic code specifying the local system's reason for the last change in session state. Values are: 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 |
NSX UI에서 확인하는 방법은 다음과 같습니다.
System > Fabric > Nodes > Host or Edge Transport Nodes
ESXi Host의 경우
Edge의 경우
Tier-0 Gateway의 경우
Edge 상단 Router의 경우
| vyos@vyos:~$ show protocols bfd peer BFD Peers: peer 192.168.13.12 vrf default interface eth5.1613 ID: 681435353 Remote ID: 2163667405 Status: up Uptime: 3 minute(s), 30 second(s) Diagnostics: ok Remote diagnostics: ok Peer Type: configured Local timers: Detect-multiplier: 3 Receive interval: 300ms Transmission interval: 500ms Echo transmission interval: 50ms Remote timers: Detect-multiplier: 3 Receive interval: 500ms Transmission interval: 500ms Echo transmission interval: 0ms peer 192.168.13.11 vrf default interface eth5.1613 ID: 4052008042 Remote ID: 3337763264 Status: up Uptime: 3 minute(s), 30 second(s) Diagnostics: ok Remote diagnostics: ok Peer Type: configured Local timers: Detect-multiplier: 3 Receive interval: 300ms Transmission interval: 500ms Echo transmission interval: 50ms Remote timers: Detect-multiplier: 3 Receive interval: 500ms Transmission interval: 500ms Echo transmission interval: 0ms peer 192.168.12.12 vrf default interface eth4.1612 ID: 3534864524 Remote ID: 1639802836 Status: up Uptime: 3 minute(s), 30 second(s) Diagnostics: ok Remote diagnostics: ok Peer Type: configured Local timers: Detect-multiplier: 3 Receive interval: 300ms Transmission interval: 500ms Echo transmission interval: 50ms Remote timers: Detect-multiplier: 3 Receive interval: 500ms Transmission interval: 500ms Echo transmission interval: 0ms peer 192.168.12.11 vrf default interface eth4.1612 ID: 4233090250 Remote ID: 322826468 Status: up Uptime: 3 minute(s), 30 second(s) Diagnostics: ok Remote diagnostics: ok Peer Type: configured Local timers: Detect-multiplier: 3 Receive interval: 300ms Transmission interval: 500ms Echo transmission interval: 50ms Remote timers: Detect-multiplier: 3 Receive interval: 500ms Transmission interval: 500ms Echo transmission interval: 0ms |
CLI에서 확인하는 방법은 다음과 같습니다.
Host의 경우
| # nsxdp-cli bfd sessions list Remote Local local_disc remote_disc recvd sent local_state local_diag client flaps bfd_type 192.168.11.2 192.168.10.5 dc288d52 d32528e 294148 140439 up No Diagnostic vdl2 1 Tunnel 192.168.11.4 192.168.10.4 f3d8853e d799f5ab 294120 140385 up No Diagnostic vdl2 1 Tunnel 192.168.11.5 192.168.10.5 fd071d a790473 294154 140431 up No Diagnostic vdl2 1 Tunnel 192.168.11.4 192.168.10.5 88d9bfce a0cbec13 294304 140340 up No Diagnostic vdl2 1 Tunnel 192.168.11.3 192.168.10.4 21b912da e09429c9 294152 140375 up No Diagnostic vdl2 1 Tunnel 192.168.11.3 192.168.10.5 4c55ee13 d2188adf 294126 140346 up No Diagnostic vdl2 1 Tunnel 192.168.11.2 192.168.10.4 80594095 83e85c3f 294193 140411 up No Diagnostic vdl2 1 Tunnel 192.168.11.5 192.168.10.4 9fe9e391 894e7374 294030 140371 up No Diagnostic vdl2 1 Tunnel |
Edge의 경우
| edge-node-01> get bfd-sessions Sun Sep 24 2023 UTC 03:00:30.377 BFD Session Dest_port : 4784 Diag : No Diagnostic Encap : vlan Forwarding : last true (current true) Interface : 3b3a62f0-5190-50a3-bfa4-e788ed231115 Keep-down : false Last_admin_down_diag_time : 2023-09-21 08:14:24 Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_cpath_down_diag_time : 2023-09-21 08:14:25 Last_down_time : 2023-09-21 08:11:23 Last_fwd_state : NONE Last_local_down_diag : Control Detection Time Expired Last_remote_admin_down_time : 2023-09-21 08:14:24 Last_remote_down_diag : Administratively Down Last_up_time : 2023-09-21 08:14:24 Local_address : 192.168.11.4 Local_discr : 216713396 Min_rx_ttl : 1 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.11.2 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 420931353 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 4784 Diag : No Diagnostic Encap : null Forwarding : last true (current true) Interface : 00000000-0000-0000-0000-000000000000 Keep-down : false Last_admin_down_diag_time : 2023-09-21 08:14:24 Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_cpath_down_diag_time : 2023-09-21 08:14:25 Last_down_time : 2023-09-21 08:11:23 Last_fwd_state : NONE Last_local_down_diag : Control Detection Time Expired Last_remote_admin_down_time : 2023-09-21 08:14:24 Last_remote_down_diag : Administratively Down Last_up_time : 2023-09-21 08:14:25 Local_address : 192.168.1.111 Local_discr : 2216966729 Min_rx_ttl : 1 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.1.112 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 1174441332 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : MGMT State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 3784 Diag : No Diagnostic Encap : geneve Forwarding : last true (current true) Interface : 00523e2b-7462-5c81-b0fd-851280477cbe Keep-down : false Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_fwd_state : NONE Last_local_down_diag : No Diagnostic Last_remote_down_diag : No Diagnostic Last_up_time : 2023-09-22 15:14:30 Local_address : 192.168.11.4 Local_discr : 3617191339 Min_rx_ttl : 255 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.10.4 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 4091053374 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 3784 Diag : No Diagnostic Encap : geneve Forwarding : last true (current true) Interface : 795518a7-d9a5-56a3-a362-95b17e9fef35 Keep-down : false Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_fwd_state : NONE Last_local_down_diag : No Diagnostic Last_remote_down_diag : No Diagnostic Last_up_time : 2023-09-22 15:14:15 Local_address : 192.168.11.5 Local_discr : 175703155 Min_rx_ttl : 255 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.10.5 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 16582429 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 3784 Diag : No Diagnostic Encap : geneve Forwarding : last true (current true) Interface : 00e6e21c-9f5a-5dc0-9cf1-0481561600c0 Keep-down : false Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_down_time : 2023-09-21 08:11:23 Last_fwd_state : NONE Last_local_down_diag : Control Detection Time Expired Last_remote_down_diag : Control Detection Time Expired Last_up_time : 2023-09-21 08:14:25 Local_address : 192.168.11.4 Local_discr : 883874198 Min_rx_ttl : 255 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.11.3 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 3709788688 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 3784 Diag : No Diagnostic Encap : geneve Forwarding : last true (current true) Interface : 57b791cd-f8dd-520a-8283-f694c22c1a9d Keep-down : false Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_fwd_state : NONE Last_local_down_diag : No Diagnostic Last_remote_down_diag : No Diagnostic Last_up_time : 2023-09-22 15:14:15 Local_address : 192.168.11.4 Local_discr : 2697718803 Min_rx_ttl : 255 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.10.5 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 2295971790 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 3784 Diag : No Diagnostic Encap : geneve Forwarding : last true (current true) Interface : e7574317-b354-5b2a-be6b-8dc8c3bedc3b Keep-down : false Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_fwd_state : NONE Last_local_down_diag : No Diagnostic Last_remote_down_diag : No Diagnostic Last_up_time : 2023-09-22 15:14:30 Local_address : 192.168.11.5 Local_discr : 2303619956 Min_rx_ttl : 255 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.10.4 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 2682905489 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 3784 Diag : No Diagnostic Encap : geneve Forwarding : last true (current true) Interface : f70db2bd-ef1c-5686-bdd9-25367ef7437a Keep-down : false Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_down_time : 2023-09-21 08:11:23 Last_fwd_state : NONE Last_local_down_diag : Control Detection Time Expired Last_remote_down_diag : Control Detection Time Expired Last_up_time : 2023-09-21 08:14:25 Local_address : 192.168.11.5 Local_discr : 1686145680 Min_rx_ttl : 255 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.11.2 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 1016056089 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 BFD Session Dest_port : 4784 Diag : No Diagnostic Encap : vlan Forwarding : last true (current true) Interface : 09a0d694-e31f-52b6-b1ac-45fc3fbbd3b6 Keep-down : false Last_admin_down_diag_time : 2023-09-21 08:14:24 Last_cp_diag : No Diagnostic Last_cp_rmt_diag : No Diagnostic Last_cp_rmt_state : up Last_cp_state : up Last_cpath_down_diag_time : 2023-09-21 08:14:25 Last_down_time : 2023-09-21 08:11:23 Last_fwd_state : NONE Last_local_down_diag : Control Detection Time Expired Last_remote_admin_down_time : 2023-09-21 08:14:24 Last_remote_down_diag : Administratively Down Last_up_time : 2023-09-21 08:14:24 Local_address : 192.168.11.5 Local_discr : 3959973419 Min_rx_ttl : 1 Multiplier : 3 Received_remote_diag : No Diagnostic Received_remote_state : up Remote_address : 192.168.11.3 Remote_admin_down : false Remote_diag : No Diagnostic Remote_discr : 3141462920 Remote_min_rx_interval : 100 Remote_min_tx_interval : 1000 Remote_multiplier : 3 Remote_state : up Router_down : false Rx_cfg_min : 1000 Rx_interval : 1000 Session_type : TUNNEL State : up Tx_cfg_min : 100 Tx_interval : 1000 Type : IPv4 |
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