10-15-2014 11:55 PM - edited 03-07-2019 09:08 PM
On 3850 configuration guide, I came across PAgP desirable mode is not supported in the switch stack (cross-stack EtherChannel).
But on Q&A document, it mentioned 3850 supports PAgP.
Q. What cross-stack EtherChannel link bundling protocols are supported?
Thank you.
10-16-2014 06:00 AM
the statement is correct , the switch supports both etherchannel protocols you just can't use pagp if you plan on doing a cross stack etherchannel. if using pagp then both ports would have to be off the same switch in the stack , if you want to spread the channel across mutliple switches in the stack then you can only use LACP. Have no idea why they developed it like that .
10-16-2014 07:11 PM
Hi glen.grant,
Thank you for your reply. This pagp limitation also applied to 3750 cross-stack etherchannel as well. Thought Cisco has made some improvements to 3850 to overcome this.
If you read through these two Q&A for 3850 (cross-stack etherchannel) below, don't you think pagp supports cross-stack etherchannel.
● Single-chassis EtherChannel: In this EtherChannel configuration mode, all the member links of given EtherChannel on single stack-switch system.
● Cross-stack EtherChannel: In this EtherChannel configuration mode, the member links are diversified between stack switches regardless of their roles.
10-17-2014 02:58 AM
Hi, adimakmur
Cisco Catalyst 3850 Cross-Stack EtherChannel can be PAgP+ and can be used for VSS dual active detection.
In last deployment of 3850 we use Cross-Stack EtherChannel and use it as trusted for VSS dual active detection.
c6500-V#sh switch virtual dual-active pagp
PAgP dual-active detection enabled: Yes
PAgP dual-active version: 1.1
----skiped----
Channel group 106 dual-active detect capability w/nbrs
Dual-Active trusted group: Yes
Dual-Active Partner Partner Partner
Port Detect Capable Name Port Version
Te1/7/7 Yes c3850-307 Te1/1/3 1.1
Te2/7/7 Yes c3850-307 Te2/1/3 1.1
---skiped----
c6500-V#sh etherchannel 106 protocol
Protocol: PAgP
c3850-307#sh etherchannel port-channel
Channel-group listing:
----------------------
Group: 1
----------
Port-channels in the group:
---------------------------
Port-channel: Po1
------------
Age of the Port-channel = 235d:20h:50m:10s
Logical slot/port = 12/1 Number of ports = 2
GC = 0x00010001 HotStandBy port = null
Port state = Port-channel Ag-Inuse
Protocol = PAgP
Port security = Disabled
Ports in the Port-channel:
Index Load Port EC state No of bits
------+------+------+------------------+-----------
0 00 Te1/1/3 Desirable-Sl 0
0 00 Te2/1/3 Desirable-Sl 0
Time since last port bundled: 169d:04h:58m:49s Te1/1/3
Time since last port Un-bundled: 169d:05h:00m:47s Te1/1/3
10-16-2014 08:12 AM
Hello, adimakur.
Glen is correct, Cisco 3850 supports both protocols. Is this for your existing 3850 switches that you are looking to cross stack?
Kind regards.
10-16-2014 07:17 PM
Yes, planning to do cross-stack etherchannel for 3850.
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