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Maintenance Commands

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lltconfig - Low Latency Transport (LLT) Protocol configuration utility


lltconfig -h

lltconfig -c [-f file]

lltconfig [-v ] [-C clusterid] [-n systemid] [-i low_high] [-x low_high] [-o]

lltconfig -t devtag -d device [-b link_type -s SAP -m mtu]

lltconfig [-u device_tag]

lltconfig -U

lltconfig -V

lltconfig [-T timer:value]

lltconfig [-F limit:value]

lltconfig -a list | flush | delete | set [system] [ device_tag] [ address]

lltconfig -K 0 | 1 | 10 | 2 | 20

lltconfig -E 0 | 1 | 3

lltconfig -A 0 | 1


The lltconfig utility initializes and maintains the configuration of the LLT protocol stack. It is responsible for managing the STREAMS plumbing between the LLT protocol driver and the network drivers to which it is connected, as well as many internal protocol parameters.

At system startup, lltconfig reads the /etc/llttab file to determine the local system ID and network devices, links the drivers, checks if there is another node with the same node id and then sets parameter information into LLT and starts the protocol running.

The lltconfig command without options reports the running status of the LLT protocol. The lltconfig command listens for 5 seconds on each link to see if it can detect a duplicate node in the cluster. It detects a duplicate node it prints an error message and exits.


-a list | flush | delete | set [system] [device_tag] [address]

Display or manipulate MAC addresses associated with specific systems on specific network links. The option list displays the address table. flush deletes all automatically learned addresses. delete removes one address as specified by the systemid and the device_tag. set adds one address for the system with the systemid on the link specified by device_tag. address should consist of hexadecimal digits separated by colons (:) or dots (.), depending on the link type.
-b link_type
Choose the link type required: "ether."
Set the clusterid. This option is needed only if more than one cluster is sharing network hardware being used by LLT. In this case, each cluster needs its own clusterid (or, alternately, a unique SAP), so that the clusters do not interfere with each other. Systems with different cluster ids cannot communicate with each other. The default cluster ID is 0.
Configure the LLT protocol from the /etc/llttab file.
-d device
Configure a network interface link below LLT. This link is bound to the LLT SAP and is used to send heartbeats and data to other systems. device is the name of the network device; it may be followed by a colon (:) and an integer specifying which unit or PPA to attach to (for example, -d /dev/qfe:1 ).
Specify an alternate configuration file to use instead of /etc/llttab. This option is valid only with the -c option.
-F limit:value
Query or change the values of the flow control limits. Valid values for limit are query, lowwater, highwater, window, ackval, sws, and linkburst. The limits are the low water mark, high water mark, and window size, respectively. The value is specified in number of packets, and is not used with the query option. The values should not be changed haphazardly, or the protocol may fail to operate.
Display a help message and exit.
-i low-high
Set a range, low-high, of system ids valid for participation in the cluster. This command alters the limits of system ids that applications may use to prevent them from trying to communicate with non-existent systems. The default is to include 0-nn, where nn is the maximum supported systemid as determined by the kernel configuration.
Used only with the -d option, this option specifies that the network link is to be used only as a last resort for sending data, although it is used to send heartbeats.
-m mtu
Specify the maximum transmission unit to use for packets on the network links. This number must be less than or equal to the lowest MTU of all the network links. The current default is 1500. Packets having a value greater than this number are submitted to LLT as fragments.
-n systemid
Set the systemid. systemid may be an integer in the range of valid systemids. It may also be a symbolic name, which is translated via /etc/llthosts to a systemid, or it may be a filename beginning with a slash (/), in which case the first word from the file is used as a symbolic name and translated via /etc/llthosts to a systemid. Systemids must be unique within a cluster. If LLT detects a configuration in which another system is using the same systemid, it disables the protocol until the system is rebooted.
Override flag. Specify that values such as systemid need to be overwritten. It can also be used to force LLT to configure a link even if a duplicate node is detected.
-s sap
Specify the SAP to bind on the network links using DLPI. The current default is 0xCAFE.
-T timer:value
Query or change the values of the protocol timers. Valid values for timer are query, heartbeat, heartbeatlo, peerinact, peertrouble, oos, retrans, service, and arp. These timers (except for query) are the heartbeat, heartbeat on low priority links, peer inactivity, link inactivity, out-of-sequence, retransmit, service procedure, and address resolution protocol cache flush timers respectively. Use lltconfig -T query to display the current timer settings. value is specified in 1/100ths of a second, and is not used with the query option. The values should not be changed haphazardly, or the protocol may fail to operate.
-t device_tag
Used only with the -d option, this option specifies a tag used to identify a particular link in subsequent commands, and is displayed by lltstat(1M).
-u device_tag
Unlink the LLT protocol from the network device indicated by device_tag.
Unlink the LLT protocol from the all network devices.
Print the LLT current and maximum supported protocol version information.
Enable verbose output.
-x low-high
Set a range, low-high, of systemids not valid for participation in the cluster. This option alters the limits of systemids that applications may use to prevent attempts to communicate with non-existent systems.
-K 0|1|10|2|20
Set checksum mode.
When set to 1, LLT checksums each packet it sends to peer to guard against packet corruption on-the-wire. LLT will also offload checksum calculation to hardware if the underlying NIC supports it. In case checksum verification fails on the receiver LLT will drop that packet causing the sender to retransmit it.

Setting to 10 is same as setting to 1 except that LLT will strictly do checksums in software and will NOT offload checksumming to NIC even if it is capable of doing so.

When set to 2, LLT also checksums the whole data buffer submitted by the client to be verified by the peer before delivering it to peer-client. In case the checksum verification fails on the receiver, LLT will panic the machine. This is purposefully done to help in analysis of memory corruption from a crash dump.

Setting to 20 is same as setting to 2 except that LLT will strictly do checksums in software and will NOT offload checksumming to NIC even if it is capable of doing so.

Level 2 and level 20 checksums should only be used when diagnosing memory corruption under the advisement of the support center, since it does have the ability to panic the machine.

The default is 0 (no checksums) as LLT depends on the NIC's hardware to guarantee packet accuracy. Level 1 checksums may be enabled if the private network is suspected of packet corruption on-the-wire or in the NIC. There may be some tradeoff of peformance due to the CPU cycles needed to perform the checksum in addition to those performed by the NIC hardware.

Currently checksum offloading is only implemented on Linux and only for transmitting packets.

-E 0|1|3
Set trace level.
If set to 1 (the default), LLT will trace all events (upcalls, flow-control, link and connection state changes) in an internal circular buffer (called as trace buffer).

When set to 3, LLT will also trace packets that are received or transmitted. This has an overhead and may impact performance. Hence should be used only to debug.

Setting to 0 disables tracing.
-A 0|1
Enable strict source address checking.
If set to 1, LLT will check the source address of incoming packets and drop packets from unknown sources. When set to 0 this check is not performed.

This option is available only when UDP links are configured. For ethernet its a no-op.


lltconfig listens for 5 seconds on each link to detect if another node in the cluster has the same node id. To change the default value, set this environment variable to a value in seconds.


When LLT and GAB are running under a cluster manager other than VCS, configure LLT and GAB as per the cluster manager's supplementary documentation on LLT and GAB. -f option is applicable only in VCS environment.




lltstat(1M), llttab(4)

Last updated: March 2006
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