LLDP-MAD
LLDP-MAD is used to detect multiple-active VSF fragments.
When a VSF fabric existing between an active and standby member fails, LLDP-MAD determines whether a multiple active topology is in place. If LLDP-MAD is configured and a VSF split occurs, one of the VSF members will become inactive, which disables the non-VSF frontplane ports. This ensures that only one of the members will be actively forwarding traffic.
![[NOTE: ]](images/note.gif) | NOTE: Once a MAD decision has been accepted and the active member is determined, the member remains in status-quo until the VSF fabric has been repaired. |
VSF split explanation
The following sequence explains a MAD scheme for a simple 2-member, VSF virtual chassis split scenario.
When the VSF link goes down and the VSF virtual chassis splits:
The Commander member ( Fragment-A for this example) would continue to stay active.
The Standby member (Fragment B) would failover and become another commander.
Fragment-B sends an SNMP request to the downstream device seeking port status information of all non-local ports of the LACP Trunk. Non-local ports on Fragment-B refers to ports that are part of Fragment-A’s member.
Fragment-B sends 2 more SNMP queries downstream. If no response is received, the frontplane ports are shut down and turned inactive.
Alternatively, if Fragment-B receives an SNMP response:
If Fragment A links are UP, the frontplane ports will be shut down.
If Fragment-A links are DOWN, Fragment-B would stay UP.
Consider that Fragment-A is actually DOWN which has caused the split:
Request made to Fragment-B will be received by the downstream device and response will return to Fragment-B.
The downstream links to Fragment-A are DOWN therefore Fragment-B will remain UP.
Alternately, if Fragment-B is DOWN and caused the split then Fragment-A will neither send a request or act on an unsolicited response and will remain UP.
MAD readiness check
The MAD assist device must be connected over a LACP trunk interface to the VSF device. Once you configure the IP address of a MAD assist device, the VSF switch will perform a MAD readiness check to determine:
If the MAD assist device is reachable.
If a trunk interface is used to reach the device.
If the trunk interface has at least one, linked —up, physical port on each member of the VSF switch.
If the above three conditions are not met, MAD will fail to detect dual active fragments in the event of a VSF split. This error will create a log message.
| NOTE: The MAD readiness check is repeated periodically. If MAD-probe parameters have changed, an appropriate log message will be created. |
vsf lldp-mad ipv4
Syntax
[no] vsf lldp-mad ipv4 <IPV4_ADDR> v2c <COMMUNITY>
Description
Enable LLDP-MAD on the VSF device.
| NOTE: The command |
Option
| Ipv4 | Specify the IPv4 address of the MAD device. |
| IPV4_ADDR | The IPv4 address of the MAD device. |
| v2c | Specify the SNMP version for the MAD device. |
| COMMUNITY | The SNMP community string for the MAD device. |
Usage
hp-vsf-sws(config)# vsf lldp-mad ipv4
hp-vsf-sws(config)# vsf lldp-mad ipv4 <IPv4_ADDR>
hp-vsf-sws(config)# vsf lldp-mad ipv4 <MAD-IP-ADDRESS> v2c
hp-vsf-sws(config)# vsf lldp-mad ipv4
210.10.0.12 v2c <COMMUNITY-STR>
Validation rules
Validation |
Error/Warning/Prompt |
|---|---|
This command cannot be executed if VSF is not enabled. |
VSF is not enabled. |
Cannot configure VSF LLDP MAD IP address because the specified IP address is a multicast IP address. Cannot configure VSF LLDP MAD IP address because the specified IP address is a link-local IP address. Cannot configure VSF LLDP MAD IP address because the specified IP address is configured on the loopback interface. Cannot configure VSF LLDP MAD IP address because the specified IP address is configured on a local interface. | |
The MAD assist device and the VSF device must be on a common IP subnet for LLDP-MAD to work. |
The MAD (Multi-Active Detection) device and the VSF device are not on the same network. |
show vsf lldp-mad [parameters | status]
Syntax
show vsf lldp-mad
[parameters | status]
Description
Show the VSF LLDP-MAD information on the switch.
Options
| lldp-mad | VSF LLDP-MAD |
| parameters | Shows the MAD-assist configuration as well as the readiness state of the switch. |
| status | Shows the current state of the MAD probe. |
Usage
show vsf lldp-mad parameters
show vsf lldp-mad status
VSF re-join after a split
If split fragment(s) re-join the VSF and become a single device, MAD readiness checks will be re-run and a fresh set of readiness parameters determined.
| NOTE: One of the devices will reboot to join the VSF. |
MAD assist device requirements
A MAD assist device must have support for LACP (IEEE 802.1AX) LAG interfaces.
It should be SNMPv2 enabled and community information must be configured on the VSF device as part of MAD configuration.
It should have support for LLDP (IEEE 802.1ab rev) and the basic management
TLVset as defined there in.It should support
SNMP GETaccess to the LLDP remote MIB (IEEE 802.1AB D13) and theifTableMIB (RFC 2683). Aruba switches have LLDP enabled by default.Support for ARP is assumed.
Limitations of MAD
The operating limitations of this feature are listed below.
MAD will work with other vendor downstream/upstream devices that have an IEEE 802.1AX (formerly 802.3ad) standards based LACP trunk to the VSF pair.
MAD can not work with non-LACP and DT-LACP trunks that Provision OS supports today.
MAD should be configured when a VSF virtual chassis is active and not after a VSF virtual chassis split. Configuring MAD after a VSF split has occurred wouldn’t help detecting multiple-active fragments for the current split event.
Upon a split and once a fragment has been determined to become inactive, it cannot subsequently become active if the originally determined ‘active’ fragment goes ‘down’. This is because the front plane (non-VSF) ports of the inactive fragment would have been brought ‘down’ and there is no way to do an LLDP-MAD subsequently.
The MAD assist device (downstream or upstream device) and the VSF device must belong to the same IPv4 subnet for MAD to work. This would be validated at the time of MAD configuration (in the UI).
The downstream/upstream helper device must support SNMPv2 and be able to handle ifTable MIB object GET requests via SNMPv2 (RFC 2863). For the first VSF release, LLDP-MAD will not work with SNMPv3.
Determination of the active/inactive fragment via MAD would take up anywhere between 2-6 seconds.
LLDP BPDU transmission on VSF enabled OOBM ports is currently not supported.