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BigIron RX Series Configuration Guide
905
53-1002253-01
Chapter
29
BiDirectional Forwarding Detection (BFD)
The BigIron RX provides support for Bidirectional Forwarding Detection (BFD), which defines a
method of rapid detection of the failure of a forwarding path by checking that the next hop router is
alive. Without BFD enabled, it can take from 3 to 30 seconds to detect that a neighboring router is
not operational causing packet loss due to incorrect routing information at a level unacceptable for
real-time applications such as VOIP and video over IP. Using BFD, you can detect a forwarding path
failure in 300 milliseconds or less depending on your configuration.
A BFD session is automatically established when a neighbor is discovered for a protocol provided
that BFD is enabled on the interface on which the neighbor is discovered and BFD is also enabled
for the protocol (by interface or globally). Once a session is set-up, each router transmits control
messages at a high rate of speed that is negotiated by the routers during the session setup. To
provide a detection time of 150 milliseconds, it is necessary to process 20 messages per second of
about 70 to 100 bytes each per each session. A similar number of messages also needs to be
transmitted out per each session. Once a session is set-up, that same message is continuously
transmitted at the negotiated rate and a check is made that the expected control message is
received at the agreed frequency from the neighbor. If the agreed upon messages are not received
from the neighbor within a short period of time, the neighbor is considered to be down. The
maximum number of sessions supported on an interface module (LP) is 20 while the maximum per
system is 100.
NOTE
BFD session establishment on an interface does not start until 90 seconds after the interface
comes up. The reason for this delay is to ensure that the link is not effected by unstable link
conditions which could cause BFD to flap. This delay time is not user configurable.
The BFD Control Message is an UDP message with destination port 3784.
NOTE
BFD version 0 is not supported in this implementation and BFD version 1 is not compatible with BFD
version 0.
NOTE
BFD supports multi-slot trunks in cases where all BFD packet are transmitted only on a single path
which does not change unless the trunk active membership changes. BFD is not be supported on
multi-slot trunks where per-packet switching is used such that the path taken by the BFD packets
will vary per packet.
Configuring BFD parameters
When you configure BFD you must set timing and interval parameters. These are configured on
each interface. When two adjacent interfaces with BFD are configured, they negotiate the
conditions for determining if the connection between them is still active. The following command is
used to set the BFD parameters.
Содержание BigIron RX Series
Страница 100: ...24 BigIron RX Series Configuration Guide 53 1002253 01 Logging on through the Web Management Interface 2 ...
Страница 192: ...116 BigIron RX Series Configuration Guide 53 1002253 01 Configuring authentication method lists 4 ...
Страница 228: ...152 BigIron RX Series Configuration Guide 53 1002253 01 Enabling WAN PHY mode support 6 ...
Страница 312: ...236 BigIron RX Series Configuration Guide 53 1002253 01 Displaying IP information 7 ...
Страница 356: ...280 BigIron RX Series Configuration Guide 53 1002253 01 Resetting LLDP statistics 9 ...
Страница 402: ...326 BigIron RX Series Configuration Guide 53 1002253 01 Transparent firewall mode 11 ...
Страница 432: ...356 BigIron RX Series Configuration Guide 53 1002253 01 SuperSpan 12 ...
Страница 500: ...424 BigIron RX Series Configuration Guide 53 1002253 01 MRP CLI example 14 ...
Страница 580: ...504 BigIron RX Series Configuration Guide 53 1002253 01 Configuring multicast traffic engineering 18 ...
Страница 591: ...BigIron RX Series Configuration Guide 515 53 1002253 01 Displaying traffic reduction 19 ...
Страница 592: ...516 BigIron RX Series Configuration Guide 53 1002253 01 Displaying traffic reduction 19 ...
Страница 598: ...522 BigIron RX Series Configuration Guide 53 1002253 01 Viewing Layer 2 ACLs 20 ...
Страница 656: ...580 BigIron RX Series Configuration Guide 53 1002253 01 Trunk formation 22 ...
Страница 754: ...678 BigIron RX Series Configuration Guide 53 1002253 01 Displaying RIP filters 24 ...
Страница 814: ...738 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPF information 25 ...
Страница 932: ...856 BigIron RX Series Configuration Guide 53 1002253 01 Generalized TTL security mechanism support 26 ...
Страница 980: ...904 BigIron RX Series Configuration Guide 53 1002253 01 Clearing IS IS information 28 ...
Страница 1000: ...924 BigIron RX Series Configuration Guide 53 1002253 01 Using secure copy 30 ...
Страница 1088: ...1012 BigIron RX Series Configuration Guide 53 1002253 01 IP source guard 35 ...
Страница 1108: ...1032 BigIron RX Series Configuration Guide 53 1002253 01 Reading CDP packets 37 ...
Страница 1126: ...1050 BigIron RX Series Configuration Guide 53 1002253 01 Clearing sFlow statistics 39 ...
Страница 1140: ...1064 BigIron RX Series Configuration Guide 53 1002253 01 802 1s Multiple Spanning Tree Protocol 40 ...
Страница 1324: ...1248 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPFv3 information 48 ...
Страница 1363: ...BigIron RX Series Configuration Guide 1287 53 1002253 01 Continuous System Monitor 51 ...
Страница 1364: ...1288 BigIron RX Series Configuration Guide 53 1002253 01 Continuous System Monitor 51 ...
Страница 1404: ...1328 BigIron RX Series Configuration Guide 53 1002253 01 Commands That Require a Reload D ...
Страница 1458: ...1382 BigIron RX Series Configuration Guide 53 1002253 01 VSRP E ...