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Understanding Multichassis Link Aggregation Group Configuration Consistency Check

 

When there is a Multichassis Link Aggregation Group (MC-LAG) inconsistency, you are notified and can take action to resolve it. An example of an inconsistency is configuring identical chassis IDs on both peers instead of configuring unique chassis IDs on both peers. Only committed MC-LAG parameters are checked for consistency.

Benefits of Using MC-LAG Consistency Check

  • This feature helps you find configuration-parameter inconsistencies between multichassis link aggregation group (MC-LAG) peers.

How MC-LAG Consistency Checks Work

The following events take place during configuration consistency check after you issue a commit on the local MC-LAG peer:

  1. Commit an MC-LAG configuration on the local MC-LAG peer.

  2. ICCP parses the MC-LAG configuration and then sends the configuration to the remote MC-LAG peer.

  3. The remote MC-LAG peer receives the MC-LAG configuration from the local MC-LAG peer and compares it with its own MC-LAG configuration.

    If the there is a severe inconsistency between the two MC-LAG configurations, the MC-LAG interface is brought down, and syslog messages are issued.

    If there is a moderate inconsistency between the two configurations, syslog messages are issued.

The following events take place during configuration consistency check after you issue a commit on the remote MC-LAG peer:

  • Commit an MC-LAG configuration on the remote MC-LAG peer.

  • ICCP parses the MC-LAG configuration and then sends the configuration to the local MC-LAG peer.

  • The local MC-LAG peer receives the configuration from the remote MC-LAG peer and compares it with its own configuration.

    If the there is a severe inconsistency between the two configurations, the MC-LAG interface is brought down, and syslog messages are issued.

    If there is a moderate inconsistency between the two configurations, syslog messages are issued.

Configuration Consistency Requirements

There are different configuration consistency requirements depending on the MC-LAG parameters. The consistency requirements are either identical or unique, which means that some parameters must be configured identically and some must be configured uniquely on the MC-LAG peers. For example, the chassis ID must be unique on both peers, whereas the LACP mode must be identical on both peers.

The enforcement level of the consistency requirements (identical or unique) is either mandatory or desired. When the enforcement level is mandatory, and you configure the MC-LAG parameter incorrectly, the system brings down the interface and issues a syslog message.

For example, you receive a syslog message that says, “Some of the Multichassis Link Aggregation (MC-LAG) configuration parameters between the peer devices are not consistent. The concerned MC-LAG interfaces were explictly brought down to prevent unwanted behavior.” When you correct the inconsistency, and issue a successful commit, the system will bring up the interface. When the enforcement is desired, and you configure the MC-LAG parameter incorrectly, you receive a syslog message that says, "Some of the Multichassis Link Aggregation(MC-LAG) configuration parameters between the peer devices are not consistent. This may lead to sub-optimal performance of the feature." As noted in the syslog message, performance will be sub-optimal in this situation. You can also issue the show interfaces mc-ae command to display the configuration consistency check status of the multichassis aggregated Ethernet interface.

If there are multiple inconsistencies, only the first inconsistency is shown. If the enforcement level for an MC-LAG parameter is mandatory, and you did not configure that parameter correctly, the command shows that the MC-LAG interface is down.

When Remote Peers are Not Reachable

When you issue a commit on the local peer, and the remote peer is not reachable, configuration consistency check will pass so that the local peer can come up in standalone mode. When the remote peer comes up, ICCP exchanges the configurations between the peers. If the consistency check fails, the MC-LAG interface goes down, and the system notifies you of the parameter that caused the inconsistency. When you correct the inconsistency, and issue a successful commit, the system brings up the interface.

Enabling MC-LAG Configuration Consistency Checking

Consistency check is not enabled by default. To enable consistency check, issue the set multi-chassis mc-lag consistency-check command.

Table 1 provides a sample list of committed MC-LAG parameters that are checked for consistency, along with their consistency requirements (identical or unique), hierarchies in which the parameters are configured, and the consistency check enforcement levels (mandatory or desired).

Table 1: MC-LAG Parameters Checked for Configuration Consistency

Configuration Knob

Hierarchy

Consistency Requirement

Enforcement

session-establishment-hold-time

Specify the time during which an Inter-Chassis Control Protocol (ICCP) connection must be established between peers.

Global, ICCP Peer

Identical

Mandatory

mac-limit

Specify the maximum number of MAC addresses to be associated with a VLAN—the default is unlimited, which can leave the network vulnerable to flooding.

Global

Identical

Desired

mac-aging-timer

Specify how long MAC addresses remain in the Ethernet switching table.

Global

Identical

Desired

arp-aging-timer

Specify the ARP aging timer in minutes for a logical interface of inet.

Global

Identical

Desired

rstp-system-identifier

Specify different bridge identifiers for different RSTP routing instances.

Global

Identical

Desired

mstp-system-identifier

Specify different bridge identifiers for different MSTP routing instances.

Global

Identical

Desired

rstp-bridge-priority

Determine which bridge is elected as the root bridge for RSTP. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.

Global

Identical

Desired

mstp-bridge-priority

Determine which bridge is elected as the root bridge for MSTP. If two bridges have the same path cost to the root bridge, the bridge priority determines which bridge becomes the designated bridge for a LAN segment.

Global

Identical

Desired

rstp-bpdu-block-on-edge

Configure bridge protocol data unit (BPDU) protection on all edge ports of a switch for RSTP.

Global

Identical

Desired

vstp-bpdu-block-on-edge

Configure bridge protocol data unit (BPDU) protection on all edge ports of a switch for VSTP.

Global

Identical

Desired

mstp-bpdu-block-on-edge

Configure bridge protocol data unit (BPDU) protection on all edge ports of a switch for MSTP.

Global

Identical

Desired

service-id

Specify a service identifier for each multichassis aggregated Ethernet interface that belongs to a link aggregation group (LAG).

Global

Identical

Mandatory

bfd minimum-interval

Configure the minimum interval after which the local routing device transmits hello packets and then expects to receive a reply from a neighbor with which it has established a BFD session.

ICCP Peer

Identical

Mandatory

iccp/minimum-transmit-interval

Specify the minimum interval at which the local routing device transmits hello packets to a neighbor with which it has established a BFD session.

ICCP Peer

Identical

Mandatory

iccp/minimum-receive-interval

Specify the minimum interval after which the local routing device must receive a reply from a neighbor with which it has established a BFD session.

ICCP Peer

Identical

Mandatory

iccp/bfd multiplier

Configure the number of hello packets not received by a neighbor that causes the originating interface to be declared down.

ICCP Peer

Identical

Mandatory

iccp single-hop

Configure single hop BFD sessions.

ICCP Peer

Identical

Mandatory

iccp/authentication-key

Specify the authentication key password to verify the authenticity of packets sent from the peers hosting an MC-LAG.

ICCP Peer

Identical

Mandatory

redundancy-group-id-list

Specify the redundancy group identification number. The Inter-Chassis Control Protocol (ICCP) uses the redundancy group ID to associate multiple chassis that perform similar redundancy functions.

ICCP Peer

Identical

Mandatory

backup-liveness-detection

Determine whether a peer is up or down by exchanging keepalive messages over the management link between the two Inter-Chassis Control Protocol (ICCP) peers.

ICCP Peer

Unique

Mandatory

mc-ae-id

Specify the identification number of the MC-LAG device.

MCAE ifd

Identical

Mandatory

mcae redundancy-group

Used by ICCP to associate multiple chassis that perform similar redundancy functions and to establish a communication channel so that applications on peering chassis can send messages to each other.

MCAE ifd

Identical

Mandatory

mcae chassis-id

Used by LACP for calculating the port number of the MC-LAG's physical member links.

MCAE ifd

Unique

Mandatory

mcae deployment mode

Indicates whether an MC-LAG is in active-standby mode or active-active mode.

MCAE ifd

Identical

Mandatory

mcae status-control

Specify whether the chassis becomes active or remains in standby mode when an interchassis link failure occurs.

MCAE ifd

Unique

Mandatory

force-icl-down

Specify that if the ICCP peer goes down, the system brings down the interchassis-link logical interface.

MCAE ifd

Unique

Mandatory

prefer-status-control-active

Specify that the node configured as status-control active becomes the active node if the peer of this node goes down.

MCAE ifd

Unique

Desired

lacp mode

Specify LACP is active or passive.

MCAE ifd

Identical

Mandatory

lacp periodic

Specify the interval for periodic transmission of LACP packets.

MCAE ifd

Identical

Mandatory

lacp system-id

Define the LACP system identifier at the aggregated Ethernet interface level.

MCAE ifd

Identical

Mandatory

lacp admin-key

Specify an administrative key for the router or switch.

MCAE ifd

Identical

Mandatory

native-vlan-id

Configure mixed tagging support for untagged packets on a port.

MCAE ifd

Identical

Mandatory

mcae-mac-synchronize

Synchronize the MAC addresses for the Layer 3 interfaces of the switches participating in the MC-LAG.

VLAN

Identical

Mandatory

Interface mac Limit

Configure a limit to the number of MAC addresses that can be learned from a bridge domain, VLAN, virtual switch, or set of bridge domains or VLANs.

VLAN

Identical

Desired

l3-interface

Associate a Layer 3 interface with the VLAN.

VLAN

Identical

Desired

igmp-snooping

Enable IGMP snooping. A Layer 2 device monitors the IGMP join and leave messages sent from each connected host to a multicast router. This enables the Layer 2 device to keep track of the multicast groups and associated member ports. The Layer 2 device uses this information to make intelligent decisions and to forward multicast traffic to only the intended destination hosts.

VLAN

Identical

Mandatory

family

Specify the protocol family configured on the logical interface.

IRB Interface

Identical

Mandatory

ipv4 address

Specify an IPv4 address for the IRB interface.

IRB Interface

Unique

Mandatory

ipv6 address

Specify an IPv6 address for the IRB interface.

IRB Interface

Unique

Mandatory

vrrp-group id

Specify a VRRP group identifier.

IRB Interface

Identical

Mandatory

proxy-arp-type

For Ethernet interfaces only, configure the router or switch to respond to any ARP request, as long as the router or switch has an active route to the ARP request target address.

IRB Interface

Identical

Mandatory

vrrp-group priority

Configure a Virtual Router Redundancy Protocol (VRRP) router priority for becoming the primary default router. The router with the highest priority within the group becomes the primary.

VRRP Group

Unique

Mandatory

vrrp-group authentication-key

Configure a Virtual Router Redundancy Protocol (VRRP) IPv4 authentication key. You also must specify a VRRP authentication scheme by including the authentication-type statement.

VRRP Group

Identical

Mandatory

vrrp-group authentication-type

Enable Virtual Router Redundancy Protocol (VRRP) IPv4 authentication and specify the authentication scheme for the VRRP group.

VRRP Group

Identical

Mandatory

vrrp-group virtual-address

Configure the addresses of the virtual routers in a Virtual Router Redundancy Protocol (VRRP) IPv4 or IPv6 group.

VRRP Group

Identical

Mandatory

encapsulation

Configure a logical link-layer encapsulation type.

MCAE ifd

Identical

Mandatory

flexible-vlan-tagging

Support simultaneous transmission of 802.1Q VLAN single-tag and dual-tag frames on logical interfaces on the same Ethernet port, and on pseudowire logical interfaces.

MCAE ifd

Identical

Mandatory

vlan-tagging

For Fast Ethernet and Gigabit Ethernet interfaces, aggregated Ethernet interfaces configured for VPLS, and pseudowire subscriber interfaces, enable the reception and transmission of 802.1Q VLAN-tagged frames on the interface.

MCAE ifd

Identical

Mandatory

mtu

Specify the maximum transmission unit (MTU) size for the media or protocol.

MCAE ifd, ICL ifd

Identical

Mandatory

interface-mode

Determine whether the logical interface accepts or discards packets based on VLAN tags.

MCAE ifl

Identical

Mandatory

vlan membership

Specify the name of the VLAN that belongs to an interface.

MCAE ifl

Identical

Mandatory

Learning the Status of a Configuration Consistency Check

The following commands provide information regarding the status of configuration consistency check:

  • Issue the show multi-chassis mc-lag configuration-consistency list-of-parameters command to view the list of committed MC-LAG parameters that are checked for inconsistencies, the consistency requirement (identical or unique), and the enforcement level (mandatory or desired).

  • Issue the show multi-chassis mc-lag configuration-consistency command to view the list of committed MC-LAG parameters that are checked for inconsistencies, the consistency requirement (identical or unique), the enforcement level (mandatory or desired), and the result of the configuration consistency check. The results are either pass or fail.

  • Issue the show multi-chassis mc-lag configuration-consistency global-config command to view configuration consistency check status for all global configuration related to MC-LAG functionality, the consistency requirement (identical or unique), the enforcement level (mandatory or desired), and the result of the configuration consistency check. The results are either pass or fail..

  • Issue the show multi-chassis mc-lag configuration-consistency icl-config command to view configuration consistency check status for parameters related to the interchassis control link, the consistency requirement (identical or unique), the enforcement level (mandatory or desired), and the result of the configuration consistency check. The results are either pass or fail.

  • Issue the show multi-chassis mc-lag configuration-consistency mcae-config command to view configuration consistency check status for parameters related to the multichassis aggregated Ethernet interface, the consistency requirement (identical or unique), the enforcement level (mandatory or desired), and the result of the configuration consistency check. The results are either pass or fail.

  • Issue the show multi-chassis mc-lag configuration-consistency vlan-config command to view configuration consistency check status for parameters related to VLAN configuration, the consistency requirement (identical or unique), the enforcement level (mandatory or desired), and the result of the configuration consistency check. The results are either pass or fail..

  • Issue the show multi-chassis mc-lag configuration-consistency vrrp-config command to view configuration consistency check status for parameters related to VRRP configuration, the consistency requirement (identical or unique), the enforcement level (mandatory or desired), and the result of the configuration consistency check. The results are either pass or fail.

  • Issue the show interfaces mc-ae command to view configuration consistency check status of the multichassis aggregated Ethernet interface. If there are multiple inconsistencies, only the first inconsistency is shown. If the enforcement level for the MC-LAG parameter is mandatory, and you did not configure that parameter correctly, the command will show that the MC-LAG interface is down.

Support for MC-LAG Configuration Consistency Checking

Both EX Series switches and QFX Series switches support MC-LAG configuration consistency checking.

Starting with Junos OS Release 15.1X53-D60 on QFX10000 switches, configuration consistency check uses the Inter-Chassis Control Protocol (ICCP) to exchange MC-LAG configuration parameters (chassis ID, service ID, and so on) and checks for any configuration inconsistencies across MC-LAG peers.

Release History Table
Release
Description
Starting with Junos OS Release 15.1X53-D60 on QFX10000 switches, configuration consistency check uses the Inter-Chassis Control Protocol (ICCP) to exchange MC-LAG configuration parameters (chassis ID, service ID, and so on) and checks for any configuration inconsistencies across MC-LAG peers.