Detecting Peer Reachability With Bfd - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

If you set the value to 1, the router installs the single best route in the IP routing
table. If you set the value greater than 1, the router installs that number of parallel
routes.
maximum-paths

Detecting Peer Reachability with BFD

You can configure a Bidirectional Forwarding Detection (BFD) session with a BGP
neighbor or peer group to determine relatively quickly whether the neighbor or peer
group is reachable. For more information on BFD, see JUNOSe IP Services Configuration
Guide. BFD is supported only for single-hop IBGP and EBGP sessions with either IPv4
or IPv6 neighbors in the core or within a VRF. BFD is not supported for multi-hop
BGP sessions (IBGP multi-hop or EBGP multi-hop). BFD behavior is identical for IBGP
and EBGP single-hop sessions, and for IPv4 and IPv6 neighbors.
When you configure BFD for a BGP session, the normal BGP keepalive mechanism
is not disabled. Unless you configure BGP not to do so, BGP still sends keepalive
messages and brings the BGP session down if the holdtimer expires.
When you configure this feature, BGP requests BFD to start a BFD protocol session
as soon as the BGP session enters the established state. BGP allows the BFD protocol
session to come up only when the source address of received BFD packets matches
the destination address of the BGP neighbor. When the BFD protocol session comes
up, BGP logs this event and reports the session in subsequent show commands. If
Use to set the maximum number of equal-cost multipaths.
Specify a value in the range 1–16; the default value is 1.
If you do not specify a keyword, the maximum number applies only to routes
learned from external peers. If you specify the ibgp keyword, the maximum
number applies only to routes received from internal peers. If you specify the
eibgp keyword (valid only for VRF IPv4 unicast or IPv6 unicast address families),
the maximum number applies to routes received from internal peers and external
peers.
This command takes effect immediately; it does not bounce the session.
You can specify the maximum number of equal-cost multipaths in the context
of the virtual router, an IPv4 unicast or IPv6 unicast address family, or a VRF
specified in the context of an IPv4 unicast or IPv6 unicast address family.
This command is not supported for VPNv4 or VPNv6 address families.
Example 1
host1(config-router)#maximum-paths 3
Example 2
host1:vr1(config-router-af)#maximum-paths ibgp 5
Use the no version to restore the default value, 1.
See maximum-paths.
Chapter 1: Configuring BGP Routing
Detecting Peer Reachability with BFD
141