09-05-2012 01:46 PM - edited 03-07-2019 08:43 AM
I've got LACP-enabled port-channels between a Cisco 3750 stack and a few different switches (some Cisco 3750s and some Juniper EX2200s). The Ciscos are all sending slow LACP updates, the Junipers are sending fast LACP updates (but the Cisco they connect with is responding with slow LACP updates).
I have a couple of questions:
1) what are the pros and cons of slow vs fast updates? my research has led me to the conclusion that fast updates are better for network resiliency as long as you have plenty of bandwidth overhead (which I do at the moment). is there anything to add to this conclusion?
2) is there any way to configure the Cisco 3750s for fast updates?
Thanks in advance for any advice!
12-11-2012 01:16 PM
Hi Mate,
AFAIK cisco does support fast LACP packets. you might want issue show lacp internal.
Also if its feasible a debug.
Thanks,
vibs
ccie-dash.blogspot.com
12-11-2012 02:12 PM
Here's all the relevant configuration information. Notice how the 'show lacp internal' shows the switch requesting slow LACP updates and the 'show lacp neighbor' shows the neighbor switch requesting fast updates. I haven't been able to find any way to set the Cisco switch to request fast LACP updates.
switch#show run int gi1/0/9
Building configuration...
Current configuration : 184 bytes
!
interface GigabitEthernet1/0/9
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 10 mode active
end
switch#show run int po10
Building configuration...
Current configuration : 166 bytes
!
interface Port-channel10
switchport trunk encapsulation dot1q
switchport mode trunk
end
switch#show lacp 10 int
switch#show lacp 10 internal
Flags: S - Device is requesting Slow LACPDUs
F - Device is requesting Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode
Channel group 10
LACP port Admin Oper Port Port
Port Flags State Priority Key Key Number State
Gi1/0/9 SA bndl 32768 0xA 0xA 0x10A 0x3D
Gi2/0/9 SA bndl 32768 0xA 0xA 0x20A 0x3D
switch#show lacp 10 nei
switch#show lacp 10 neighbor
Flags: S - Device is requesting Slow LACPDUs
F - Device is requesting Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode
Channel group 10 neighbors
Partner's information:
LACP port Admin Oper Port Port
Port Flags Priority Dev ID Age key Key Number State
Gi1/0/9 FA 127 a8d0.e5bc.d780 7s 0x0 0x1 0x1 0x3F
Gi2/0/9 FA 127 a8d0.e5bc.d780 7s 0x0 0x1 0x2 0x3F
12-11-2012 10:12 PM
Cool
please use the following
conf t
interface GigabitEthernet1/0/9
lacp rate fast
end
Hope this helps
04-03-2016 04:25 PM
I realize this thread is 4 years old, however I had this same issue, and hope this information will help somebody else.
The 3750 only supports slow LACP. The rate for this is every 30 seconds.
The 6500 series will support a "Fast" or 1 second LACP rate.
07-17-2017 10:43 PM
FYI "lacp rate fast" is supported on the 15.2(4)E software train:
Switch#sh ver
Cisco IOS Software, C3750E Software (C3750E-UNIVERSALK9-M), Version 15.2(4)E4, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2017 by Cisco Systems, Inc.
Compiled Wed 05-Apr-17 04:22 by prod_rel_team
Switch#sh run int Gi1/1/1
interface GigabitEthernet1/1/1
switchport trunk encapsulation dot1q
switchport mode trunk
load-interval 30
mls qos trust dscp
lacp rate fast
channel-group 1 mode active
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