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Link aggregation (LACP) supported/non-supported configurations on SRX and EX

  [KB22474] Show Article Properties


Summary:
This article provides information about the supported LACP configuration on SRX, when connected with EX, to perform LACP.
Symptoms:
Supported LACP configuration on EX and SRX in various scenarios.
Cause:
 
Solution:
Let's consider the following example:

SRX Config:
set interfaces ge-3/0/0 gigether-options redundant-parent reth1
set interfaces ge-15/0/0 gigether-options redundant-parent reth1
set interfaces reth1 redundant-ether-options redundancy-group 1
set interfaces reth1 redundant-ether-options minimum-links 1
set interfaces reth1 redundant-ether-options lacp passive
set interfaces reth1 redundant-ether-options lacp periodic slow

EX Config:
set chassis aggregated-devices ethernet device-count 10
set interfaces ge-0/0/0 ether-options 802.3ad ae1
set interfaces ge-0/0/1 ether-options 802.3ad ae1
set interfaces ae1 aggregated-ether-options lacp active
set interfaces ae1 aggregate-ether-options lacp periodic slow

Topology:
SRX (ge-3/0/0) is connected to EX (ge-0/0/0)
SRX (ge-15/0/0) is connected to EX (ge-0/0/1)

Notice that the switch interfaces are in one LACP bundle and it is supposed to load balance; which means that it will send one packet to ge-3/0/0 and the next packet to ge-15/0/0, towards the SRX.

Assume that Node0 is active, the first packet sent to ge-3/0/0 will go through and the packet to ge-15/0/0 will be dropped as Node1 is passive.

This is a non-supported configuration.

The supported configuration would be as follows:

SRX Config:
set interfaces ge-3/0/0 gigether-options redundant-parent reth1
set interfaces ge-3/0/1 gigether-options redundant-parent reth1
set interfaces ge-15/0/0 gigether-options redundant-parent reth1
set interfaces ge-15/0/1 gigether-options redundant-parent reth1
set interfaces reth1 redundant-ether-options redundancy-group 1
set interfaces reth1 redundant-ether-options lacp passive
set interfaces reth1 redundant-ether-options lacp periodic slow


EX Config:
set chassis aggregated-devices ethernet device-count 10
set interfaces ge-0/0/0 ether-options 802.3ad ae1
set interfaces ge-0/0/2 ether-options 802.3ad ae1
set interfaces ge-0/0/1 ether-options 802.3ad ae2
set interfaces ge-0/0/3 ether-options 802.3ad ae2
set interfaces ae1 aggregated-ether-options lacp active
set interfaces ae2 aggregated-ether-options lacp active
set interfaces ae1 aggregate-ether-options lacp periodic slow
set interfaces ae2 aggregate-ether-options lacp periodic slow


Topology:
LACP ae1:
SRX (ge-3/0/0) is connected to EX (ge-0/0/0)
SRX (ge-3/0/1) is connected to EX (ge-0/0/2)

LACP ae2:
SRX (ge-15/0/0) is connected to EX (ge-0/0/1)
SRX (ge-15/0/1) is connected to EX (ge-0/0/3)

The same configuration can be done without the use of LACP on either side. SRX can do loadbalancing without using the LACP. It is only needed when the other side is configured to do LACP. 

In cases where LACP is not configured on the other side, please remove the LACP configuration from SRX in the following manner;

SRX Config: (Without LACP)
delete interfaces reth1 redundant-ether-options lacp

EX Config: (Without LACP)

delete interfaces ae1 aggregated-ether-options lacp
delete interfaces ae2 aggregated-ether-options lacp

Note:

Removing LACP from the network is associated with a downtime.
Branch devices (SRX100 to SRX650) generally show 30sec to a minute downtime, whereas high-end devices generally show an average of 5 to 6 minutes downtime.


The following diagram clearly illustrates the difference between the supported and non-supported configurations:












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