Hi @tadeosho70,
With echo mode, this is no problem. The packets you send are echoed back to you. For example, take a look at this output:
R1(config)#interface FastEthernet 0/0
R1(config-if)#bfd interval 300 min_rx 300 multiplier 3
R2(config)#interface FastEthernet 0/0
R2(config-if)#bfd interval 300 min_rx 600 multiplier 3
The min_rx is set to 300 on R1 and 600 on R2. Here’s the output of R1 showing the 600 ms of R2:
R1#show bfd neighbors details
NeighAddr LD/RD RH/RS State Int
192.168.12.2 1/1 Up Up Fa0/0
Session state is UP and using echo function with 600 ms interval.
OurAddr: 192.168.12.1
Local Diag: 0, Demand mode: 0, Poll bit: 0
MinTxInt: 1000000, MinRxInt: 1000000, Multiplier: 3
Received MinRxInt: 1000000, Received Multiplier: 3
Holddown (hits): 0(0), Hello (hits): 1000(571)
Rx Count: 578, Rx Interval (ms) min/max/avg: 1/1000/867 last: 396 ms ago
Tx Count: 580, Tx Interval (ms) min/max/avg: 1/1000/865 last: 276 ms ago
Elapsed time watermarks: 0 0 (last: 0)
Registered protocols: OSPF
Uptime: 00:08:21
Last packet: Version: 1 - Diagnostic: 0
State bit: Up - Demand bit: 0
Poll bit: 0 - Final bit: 0
Multiplier: 3 - Length: 24
My Discr.: 1 - Your Discr.: 1
Min tx interval: 1000000 - Min rx interval: 1000000
Min Echo interval: 600000
and R2:
R2#show bfd neighbors details
NeighAddr LD/RD RH/RS State Int
192.168.12.1 1/1 Up Up Fa0/0
Session state is UP and using echo function with 300 ms interval.
OurAddr: 192.168.12.2
Local Diag: 0, Demand mode: 0, Poll bit: 0
MinTxInt: 1000000, MinRxInt: 1000000, Multiplier: 3
Received MinRxInt: 1000000, Received Multiplier: 3
Holddown (hits): 0(0), Hello (hits): 1000(575)
Rx Count: 584, Rx Interval (ms) min/max/avg: 1/1000/865 last: 700 ms ago
Tx Count: 583, Tx Interval (ms) min/max/avg: 1/1000/868 last: 12 ms ago
Elapsed time watermarks: 0 0 (last: 0)
Registered protocols: OSPF
Uptime: 00:08:25
Last packet: Version: 1 - Diagnostic: 0
State bit: Up - Demand bit: 0
Poll bit: 0 - Final bit: 0
Multiplier: 3 - Length: 24
My Discr.: 1 - Your Discr.: 1
Min tx interval: 1000000 - Min rx interval: 1000000
Min Echo interval: 300000
Keep in mind that your own packets are echoed back to you, it’s not like OSPF or EIGRP where you need to receive a hello packet from your neighbor.