Posted on July 23, 2020 10:11 pm
 |  Asked by JOONHWAN CHO
 |  72 views
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Hi.

I want to know how to test lacp port-priority.

I check show lacp neighbor  and  change port-pritoiry.

ex)there is port 1,2,3.

port 1,2 priority is 100, port 3 priority 3 is 1000. but  port 3 doesn’t change  standby port.

How to  change port 3 standby port ? or test it?

In advance, thanks.

 

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Posted by Lokesh Charora
Answered on July 23, 2020 10:45 pm

Hello Joonhwan,

I am assuming all the ports are of same speed to begin with ?

LACP port priority determines the port that is active in a LAG in "fallback mode". Numerically lower
values have higher priority.If LACP negotiation fails, only the member port with the
lowest LACP priority will remain active until an LACP PDU is received by one of the member ports.

I am trying to explain this with 2 ports , please see below:

interface Port-Channel1
port-channel lacp fallback static >> This is a must config
port-channel lacp fallback timeout 30 >> This is reduced to 30 seconds for testing( default is 90 seconds).

Now port-channel1 has 2 ports(these ports are connected to different switches without LACP configured from peer side, we expect this port-channel to go into fallback mode):
Ethernet1/1
Ethernet2/1

In first scenario :

(config)#show run int et 1/1
interface Ethernet1/1
channel-group 1 mode active
lacp port-priority 40960
rbf262...18:31:24(config)#show run int et 2/1
interface Ethernet2/1
channel-group 1 mode active
lacp port-priority 8192 >>> This should be active if port-channel goes into fallback mode.

#show int po1
Port-Channel1 is up, line protocol is up (connected)
Hardware is Port-Channel, address is 7483.efeb.7bd2
Ethernet MTU 10178 bytes , BW 10000000 kbit
Full-duplex, 10Gb/s
Active members in this channel: 1
... Ethernet2/1 , Full-duplex, 10Gb/s
Fallback mode is: static
Fallback mode status: Enabled
Fallback timeout is 30 seconds
Up 1 second
16 link status changes since last clear
Last clearing of "show interface" counters never
5 minutes input rate 475 bps (0.0% with framing overhead), 1 packets/sec
5 minutes output rate 243 bps (0.0% with framing overhead), 0 packets/sec
98283 packets input, 11480344 bytes
Received 8474 broadcasts, 89809 multicast
0 input errors, 0 input discards
157843 packets output, 19620875 bytes
Sent 6874 broadcasts, 150969 multicast
0 output errors, 0 output discards

Now for testing purpose, lets make et2/1 higher port-priority and see if the result is reversed:

switch(config-if-Et2/1)#lacp port-priority 40965
switch(config-if-Et2/1)#exit
switch(config)#int po1
switch(config-if-Po1)#shut
switch(config-if-Po1)#no shut
switch(config-if-Po1)#exit

switch(config)#show int po1
Port-Channel1 is down, line protocol is lowerlayerdown (notconnect)
Hardware is Port-Channel, address is 7483.efeb.7bd2
Ethernet MTU 0 bytes
Full-duplex, Unconfigured
Active members in this channel: 0
Fallback mode is: static
Fallback mode status: Monitoring
Fallback timeout is 30 seconds
Down 21 seconds
19 link status changes since last clear
Last clearing of "show interface" counters never
5 minutes input rate 592 bps (- with framing overhead), 1 packets/sec
5 minutes output rate 573 bps (- with framing overhead), 1 packets/sec
98323 packets input, 11484975 bytes
Received 8479 broadcasts, 89844 multicast
0 input errors, 0 input discards
157908 packets output, 19629530 bytes
Sent 6874 broadcasts, 151034 multicast
0 output errors, 0 output discards

switch(config)#show int po1
Port-Channel1 is up, line protocol is up (connected)
Hardware is Port-Channel, address is 7483.efeb.7bd2
Ethernet MTU 10178 bytes , BW 10000000 kbit
Full-duplex, 10Gb/s
Active members in this channel: 1
... Ethernet1/1 , Full-duplex, 10Gb/s >>>Now et1/1 becomes active
Fallback mode is: static
Fallback mode status: Enabled
Fallback timeout is 30 seconds
Up 2 minutes, 11 seconds
20 link status changes since last clear
Last clearing of "show interface" counters never
5 minutes input rate 815 bps (0.0% with framing overhead), 1 packets/sec
5 minutes output rate 1.04 kbps (0.0% with framing overhead), 1 packets/sec
98486 packets input, 11504052 bytes
Received 8494 broadcasts, 89992 multicast
0 input errors, 0 input discards
158135 packets output, 19658061 bytes
Sent 6883 broadcasts, 151252 multicast
0 output errors, 0 output discards
switch(config)#

I hope this helps your testing.

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