BFD Scale Improvement on ES+ Line Card for 7600
Bidirectional Forwarding Detection (BFD) scale improvement feature
provides the functionality to offload a BFD session to an ES+ line card.
BFD is a forwarding path failure detection protocol and reduces the
overall network convergence time by sending rapid failure detection
packets (messages) to the routing protocols for recalculating the
routing table. Before Release 15.1(2)S, a BFD session was run as a
software component on the Route Processor (RP). Hence, the performance
of BFD was restricted to the capabilities of CPU and IOS on the RP on
the Cisco 7600 Router. Effective failure detection requires BFD to run
at high frequencies (using aggressive timers as low as 50ms), which was
not possible because of CPU and IOS restrictions. Effective with Cisco
IOS Release 15.1(2) S, apart from running a BFD session on the RP, you
can also offload a BFD session to the ES+ line card based on specific
conditions listed in the "Restrictions for BFD Scale Improvement" section.
Restrictions for BFD Scale Improvement
The following restrictionsapply for BFD scale improvement:
•
A BFD session is supported on only RSP 720 and Supervisor 720 (SUP720), it is not supported on SUP32.
A BFD session is supported on only RSP 720 and Supervisor 720 (SUP720), it is not supported on SUP32.
•Only BFD version 1 is supported.
Only BFD version 1 is supported.
•The BFD session can be offloaded only to an ES+ line card interface.
The BFD session can be offloaded only to an ES+ line card interface.
•Ensure
that the ES+ Line Card interface configured with the BFD session is on
global routing table. Effective from Cisco IOS Release 15.1(3)S and
15.1(2)S1, the interface with a BFD session can be on any Virtual
Routing and Forwarding (VRF).
Ensure
that the ES+ Line Card interface configured with the BFD session is on
global routing table. Effective from Cisco IOS Release 15.1(3)S and
15.1(2)S1, the interface with a BFD session can be on any Virtual
Routing and Forwarding (VRF).
•Each network processor supports a total of 250 sessions distributed across its ports.
Each network processor supports a total of 250 sessions distributed across its ports.
•BFD hardware offload is supported for IPv4 sessions with non-echo mode only.
BFD hardware offload is supported for IPv4 sessions with non-echo mode only.
•You can configure IPv4 and IPv6 sessions to co-exist on the router as well as the same interface.
You can configure IPv4 and IPv6 sessions to co-exist on the router as well as the same interface.
•Only
the single hop BFD hardware offload is supported for both the IPv4 and
IPv6 sessions. BFD hardware offload supports either of these
combinations for IPv4 and IPv6 sessions:
Only
the single hop BFD hardware offload is supported for both the IPv4 and
IPv6 sessions. BFD hardware offload supports either of these
combinations for IPv4 and IPv6 sessions:
–1000 IPv6 BFD sessions and no IPv4 sessions.
1000 IPv6 BFD sessions and no IPv4 sessions.
–2000 IPv4 BFD sessions and no IPv6 sessions.
2000 IPv4 BFD sessions and no IPv6 sessions.
–500 IPv4 BFD sessions and 500 IPv6 sessions.
500 IPv4 BFD sessions and 500 IPv6 sessions.
•BFD offload is supported only for the ethernet interface.
BFD offload is supported only for the ethernet interface.
•Timer
values for Tx and Rx should only be in multiples of 50 and should range
between 50 and 950ms for both the local and remote BFD peer router.
Timer
values for Tx and Rx should only be in multiples of 50 and should range
between 50 and 950ms for both the local and remote BFD peer router.
•If the Failure in MPLS core does not converge before XC BFD timer expires, then the BFD session flaps.
If the Failure in MPLS core does not converge before XC BFD timer expires, then the BFD session flaps.
•BFD Tx jitter defined in RFC 5880 is not supported.
BFD Tx jitter defined in RFC 5880 is not supported.
•You
cannot swap a BFD session between ES+ line card and IOS by changing the
parameters when the BFD session is up and running. To swap a BFD
session, you need to unconfigure and reconfigure the BFD session with
the changed parameters.
You
cannot swap a BFD session between ES+ line card and IOS by changing the
parameters when the BFD session is up and running. To swap a BFD
session, you need to unconfigure and reconfigure the BFD session with
the changed parameters.
•BFD offload is not supported on port-channel or SVI interfaces.
BFD offload is not supported on port-channel or SVI interfaces.
•In
case of prolonged network instability and BFD session flaps, the
session state may get stuck in the DOWN, INIT, or UP state. Unconfigure
and reconfigure BFD to resolve this issue.
In
case of prolonged network instability and BFD session flaps, the
session state may get stuck in the DOWN, INIT, or UP state. Unconfigure
and reconfigure BFD to resolve this issue.
•During line card OIR, the show bfd neighbor detail
command may show discrepancy in the statistics counter. The statistics
counter provide information about Rx or Tx counts for a particular
session.
During line card OIR, the show bfd neighbor detail
command may show discrepancy in the statistics counter. The statistics
counter provide information about Rx or Tx counts for a particular
session.
•BFD supports 2000 sessions with OSPF as client on RSP. Example scenarios:
BFD supports 2000 sessions with OSPF as client on RSP. Example scenarios:
–All subinterfaces are configured as point to point.
All subinterfaces are configured as point to point.
–Four instances of OSPF are running with each instance supporting 500 BFD session.
Four instances of OSPF are running with each instance supporting 500 BFD session.
•Configure
the symmetric slow timers to less than or equal to five seconds on both
the ends to bring up the HW offloaded BFD sessions.
Configure
the symmetric slow timers to less than or equal to five seconds on both
the ends to bring up the HW offloaded BFD sessions.
•BFD supports a maximum of 10 IPv6 static route sessions on an interface.
BFD supports a maximum of 10 IPv6 static route sessions on an interface.
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