A single-hop BFD session in Junos OS runs in distributed mode by default. The exceptions are OSPFv3 BFD and PIMv6 BFD. They run in centralized mode.
In this article discusses another exception for IPv6 single-hop BFD. If a user wants BFD for IPv6 static route to run in distributed mode, use global IPv6 address for next hop.
Suppose two routers enable IPv6 on a single Ethernet link.
One router has an interface configured as follows:
[edit]
falcon@smudger# show interfaces
ge-0/1/0 {
unit 0 {
family inet {
address 192.168.1.1/24;
}
family inet6 {
address abcd::1/64;
}
}
}
[edit]
falcon@smudger# run show interfaces ge-0/1/0.0 extensive | match "Protocol inet|Destination"
Protocol inet, MTU: 1500
Destination: 192.168.1/24, Local: 192.168.1.1, Broadcast: 192.168.1.255, Generation: 234
Protocol inet6, MTU: 1500
Destination: abcd::/64, Local: abcd::1
Destination: fe80::/64, Local: fe80::224:dcff:fe9b:2052
While the other router has the following configuration:
[edit]
falcon@duke# show interfaces
ge-1/1/1 {
unit 0 {
family inet {
address 192.168.1.2/24;
}
family inet6 {
address abcd::2/64;
}
}
}
[edit]
falcon@duke# run show interfaces ge-1/1/1.0 extensive | match "Protocol inet|Destination"
Protocol inet, MTU: 1500
Destination: 192.168.1/24, Local: 192.168.1.2, Broadcast: 192.168.1.255, Generation: 239
Protocol inet6, MTU: 1500
Destination: abcd::/64, Local: abcd::2
Destination: fe80::/64, Local: fe80::224:dcff:fe9b:19d
These two routers can see each other:
[edit]
falcon@duke# run show ipv6 neighbors
IPv6 Address Linklayer Address State Exp Rtr Secure Interface
abcd::2 00:24:dc:9b:01:9d stale 136 yes no ge-0/1/0.0
fe80::224:dcff:fe9b:19d 00:24:dc:9b:01:9d stale 151 yes no ge-0/1/0.0
[edit]
falcon@smudger# run show ipv6 neighbors
IPv6 Address Linklayer Address State Exp Rtr Secure Interface
abcd::1 00:24:dc:9b:20:52 stale 211 yes no ge-1/1/1.0
fe80::224:dcff:fe9b:2052 00:24:dc:9b:20:52 stale 203 yes no ge-1/1/1.0
If IPv6 static route has link-local address as next hop and BFD is configured for it:
[edit]
falcon@smudger# show routing-options
rib inet6.0 {
static {
route abc::1/128 {
qualified-next-hop fe80::224:dcff:fe9b:19d {
interface ge-0/1/0.0;
bfd-liveness-detection {
minimum-interval 500;
}
}
}
}
}
[edit]
falcon@duke# show routing-options
rib inet6.0 {
static {
route def::1/128 {
qualified-next-hop fe80::224:dcff:fe9b:2052 {
interface ge-1/1/1.0;
bfd-liveness-detection {
minimum-interval 500;
}
}
}
}
}
BFD for IPv6 static route is single-hop but it is running in centralized mode.
[edit]
falcon@smudger# run show ppm adjacencies protocol bfd detail
Protocol: BFD, Hold time: 1500, IFL-index: 321
Distributed: FALSE
BFD discriminator: 21, BFD routing table index: 0
HadExpired: FALSE, Expired-Count: 0, Largest-Interval: 506, Last Rx Interval: 426, Num Packets: 73, Absorbed Packets: 67, Rx Packet: 20 C0 03 18 00 00 00 23 00 00 00 15 00 07 A1 20 00 07 A1 20 00 00 00 00
Adjacencies: 1, Remote adjacencies: 0
[edit]
falcon@smudger# run show bfd session extensive
Detect Transmit
Address State Interface Time Interval Multiplier
fe80::224:dcff:fe9b:19d Up ge-0/1/0.0 1.500 0.500 3
Client Static, TX interval 0.500, RX interval 0.500
Session up time 00:01:29
Local diagnostic None, remote diagnostic None
Remote state Up, version 1
Session type: Single hop BFD
Min async interval 0.500, min slow interval 1.000
Adaptive async TX interval 0.500, RX interval 0.500
Local min TX interval 0.500, minimum RX interval 0.500, multiplier 3
Remote min TX interval 0.500, min RX interval 0.500, multiplier 3
Local discriminator 21, remote discriminator 35
Echo mode disabled/inactive Session ID: 0x18e
1 sessions, 1 clients
Cumulative transmit rate 2.0 pps, cumulative receive rate 2.0 pps
If you want BFD for IPv6 static route to run in distributed mode, use global IPv6 address for next hop.
[edit]
falcon@smudger# show routing-options
rib inet6.0 {
static {
route abc::1/128 {
next-hop abcd::2;
bfd-liveness-detection {
minimum-interval 500;
}
}
}
}
[edit]
falcon@smudger# run show ppm adjacencies protocol bfd detail
Protocol: BFD, Hold time: 1500, IFL-index: 321
Distributed: TRUE
BFD discriminator: 22, BFD routing table index: 0
Num Packets: 4, Absorbed Packets: 0, Rx Packet: 20 C8 03 18 00 00 00 24 00 00 00 16 00 07 A1 20 00 07 A1 20 00 00 00 00
Distribution handle: 109, Distribution address: fpc0
Adjacencies: 1, Remote adjacencies: 1
[edit]
falcon@smudger# run show bfd session extensive
Detect Transmit
Address State Interface Time Interval Multiplier
abcd::2 Up ge-0/1/0.0 1.500 0.500 3
Client Static, TX interval 0.500, RX interval 0.500
Session up time 00:00:24
Local diagnostic None, remote diagnostic None
Remote state Up, version 1
Session type: Single hop BFD
Min async interval 0.500, min slow interval 1.000
Adaptive async TX interval 0.500, RX interval 0.500
Local min TX interval 0.500, minimum RX interval 0.500, multiplier 3
Remote min TX interval 0.500, min RX interval 0.500, multiplier 3
Local discriminator 22, remote discriminator 36
Echo mode disabled/inactive
Remote is control-plane independent
Session ID: 0x18f
1 sessions, 1 clients
Cumulative transmit rate 2.0 pps, cumulative receive rate 2.0 pps