BFD for Static Routes
To use BFD for static routes, configure static routes (IPv4 or IPv6) and the
corresponding static BFD separately. When static BFD is configured, the static route
manager checks the routing table (RIBMGR) for a route to the BFD neighbor.
- If a route exists and the
next-hop is directly connected, a single-hop session is created.
- If the next-hop is not directly
connected, a multi-hop BFD session is created.
When the BFD session is up, a corresponding static route is added to RIBMGR. When the BFD
session that monitors the static route goes down because the BFD neighbor is not
reachable, static routes are removed from RIBMGR. These removed routes are replaced in
RIBMGR when the BFD neighbor is reachable.
Considerations for BFD for static
routes
- When you configure a static BFD
for a neighbor and the neighbor is reachable, a request is made to BFD to
establish a BFD session.
- BFD static route session uses the
timer values that are configured in the CLI. If these timer values conflict with
the timer values set for BGP, for the same next-hop, then BFD uses the smaller
value to meet the more stringent requirement. For more information, see BFD Session Timer Value Selection.
- After a reboot of the device,
global
config-replay happens before interface
config-replay. In such a situation, static BFD sessions can be
created before static routes are added to RIBMGR. Therefore, for SLX-OS, BFD
sessions are created only when the next-hop is reachable.
- If you remove the static BFD
session, BFD takes down the corresponding session without removing static routes
from routing table. Ongoing traffic is not interrupted.
- If a BFD session goes down
because the BFD neighbor is not reachable, the associated static routes are
removed from RIBMGR. Traffic is interrupted on these static routes.
- If the maximum number of BFD
sessions is reached, a BFD session may not come up. In such a situation, a BFD
session is not created for the related static route and the route is not removed
from RIBMGR.
BFD for IPv6 static routes
If the BFD neighbor is link-local, the source IPv6 address must also be link-local.
If an IPv6 BFD session is running for a link-local BFD neighbor, the interface-type and interface-name
parameters (for the ipv6
route static bfd command) are mandatory because the link-local address
can be the same on multiple interfaces.
Supported Platforms
BFD for static routes is supported on
SLX 9740, SLX 9250, SLX 9150,
Extreme 8820, Extreme 8720, and Extreme 8520.
