Configuring LLT over UDP


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Configuring LLT over UDP

Following is a checklist for configuring LLT over UDP. Examples are provided in the sections that follow.

Make sure that the LLT private links are on different physical networks.
If the LLT private links are not on different physical networks, then make sure that the links are on separate subnets. Set the broadcast address in /etc/llttab explicitly depending on the subnet for each link.

See Broadcast address in the /etc/llttab file.

See the examples in the following sections.
Make sure that each NIC has an IP address configured before configuring LLT.
Make sure the IP addresses in the /etc/llttab files are consistent with the IP addresses of the network interfaces.
Make sure that each link has a unique non-well known UDP port.
See Selecting UDP ports.
Set the broadcast address correctly for direct-attached (non-routed) links.
For links that cross an IP router, disable broadcast features and specify the IP address of each link manually in the /etc/llttab file.
See Sample configuration: Links crossing IP routers.

Broadcast address in the /etc/llttab file

The broadcast address is set explicitly for each link in the following example.

# cat /etc/llttab

set-node Node0

set-cluster 1

link link1 /dev/udp - udp 50000 - 10.20.30.1 10.20.30.255

link link2 /dev/udp - udp 50001 - 10.20.31.1 10.20.31.255

Verify the subnet mask using the ifconfig command to ensure that the two links are on separate subnets.

# ifconfig lan1

lan1: flags=1843<UP,BROADCAST,RUNNING,MULTICAST,CKO>

inet 10.20.30.1 netmask ffffff00 broadcast 10.20.30.255

# ifconfig lan2

lan2: flags=1843<UP,BROADCAST,RUNNING,MULTICAST,CKO>

inet 10.20.31.1 netmask ffffff00 broadcast 10.20.31.255

The link command in the /etc/llttab file

Field description for link command in /etc/llttab describes the fields of the link command shown in the /etc/llttab file examples.

See Sample configuration: Direct-attached links.

See Sample configuration: Links crossing IP routers.

Note that some of these fields differ from the command for standard LLT links.

Field description for link command in /etc/llttab

Field	Description
`<tag-name>`	A unique string that is used as a tag by LLT; for example link1, link2,....
`<device>`	The device path of the UDP protocol; for example /dev/udp.
`<node-range>`	Nodes using the link. "`-`" indicates all cluster nodes are to be configured for this link.
`<link-type>`	Type of link; must be "`udp`" for LLT over UDP.
`<udp-port>`	Unique UDP port in the range of 49152-65535 for the link. See Selecting UDP ports.
`<MTU>`	"`-`" is the default, which has a value of 8192. The value may be increased or decreased depending on the configuration. Use the `lltstat -l` command displays the current value.
`<IP address>`	IP address of the link on the local node.
`<bcast-address>`	For clusters having broadcasts enabled, specify the value of the subnet broadcast address. "`-`" is the default for clusters spanning routers.

The set-addr command in the /etc/llttab file

The set-addr command in the /etc/llttab file is required when the broadcast feature of LLT is disabled, such as when LLT must cross IP routers. Field description for set-addr command in /etc/llttab describes the fields of the set-addr command.

See Sample configuration: Links crossing IP routers.

Field description for set-addr command in /etc/llttab

Field	Description
`<node-id>`	The ID of the cluster node; for example, 0.
`<link tag-name>`	The string used by LLT to identify the link; for example link1, link2,....
`<address>`	IP address assigned to the link for the peer node.

Selecting UDP ports

When selecting a UDP port, select an available 16-bit integer from the range described below.

Use available ports (that is, ports that are not in use)] in the private range 49152 to 65535
Do not use:
- Ports from the range of well-known ports, 0 to 1023
- Ports from the range of registered ports, 1024 to 49151

To check which ports are defined as defaults for a node, examine the file /etc/services. You should also use the netstat command to list the UDP ports currently in use. For example:

# netstat -a | head -2 ; netstat -a | grep udp

Active Internet connections (including servers)

Proto Recv-Q Send-Q Local Address Foreign Address (state)

udp 0 0 *.ntalk *.*

udp 0 0 *.* *.*

udp 0 0 *.49193 *.*

udp 0 0 *.49152 *.*

udp 0 0 *.portmap *.*

udp 0 0 *.* *.*

udp 0 0 *.135 *.*

udp 0 0 *.2121 *.*

udp 0 0 *.xdmcp *.*

udp 0 0 *.49196 *.*

udp 0 0 *.* *.*

udp 0 0 *.snmp *.*

udp 0 0 *.* *.*

udp 0 0 *.49153 *.*

udp 0 0 *.echo *.*

udp 0 0 *.discard *.*

udp 0 0 *.daytime *.*

udp 0 0 *.chargen *.*

udp 0 0 *.syslog *.*

Look in the UDP section of the output; UDP ports listed under Local Address are already in use. If a port is listed in the /etc/services file, its associated name is displayed rather than the port number in the output.

Configuring LLT on subnets

You need to make sure to properly configure the netmask and broadcast address when nodes reside on different subnets.

Configuring the netmask

If you have nodes on different subnets, set the netmask so that the nodes can access the subnets in use.

For example:

For first network interface

IP address=192.168.30.1, Broadcast address=192.168.30.255, 
Netmask=255.255.255.0

For second network interface

IP address=192.168.31.1, Broadcast address=192.168.31.255, 
Netmask=Mask:255.255.255.0

Configuring the broadcast address

If you have nodes on different subnets, set the broadcast address in /etc/llttab depending on the subnet that the links are on.

An example of a typical /etc/llttab file when nodes are on different subnets. Note the explicitly set broadcast address for each link.

# cat /etc/llttab

set-node nodexyz

set-cluster 100

link link1 /dev/udp - udp 50000 - 192.168.30.1 192.168.30.255

link link2 /dev/udp - udp 50001 - 192.168.31.1 192.168.31.255

Sample configuration: Direct-attached links

The following illustration depicts a typical configuration of direct-attached links employing LLT over UDP.

Click the thumbnail above to view full-sized image.

The configuration represented by the following /etc/llttab file for Node 0 has directly attached crossover links or links connected through a hub or switch. These links do not cross routers.

Because LLT broadcasts requests peer nodes to discover their addresses, the addresses of peer nodes do not need to be specified in the /etc/llttab file using the set-addr command. For direct attached links, you do need to set the broadcast address of the links in the /etc/llttab file. Verify that the IP addresses and broadcast addresses are set correctly by using the ifconfig -a command.

set-node Node0

set-cluster 1

#configure Links

#link <tag-name> <device> <node-range> <link-type> <udp port> 
<MTU> <IP-address> <bcast-address>
 
 link link1 /dev/udp - udp 50000 - 192.1.2.1 192.1.2.255


 link link2 /dev/udp - udp 50001 - 192.1.3.1 192.1.3.255

The file for Node 1 would resemble:

set-node Node1

set-cluster 1

#configure Links

#link <tag-name> <device> <node-range> <link-type> <udp port> 
<MTU> <IP-address> <bcast-address>
 
 link link1 /dev/udp - udp 50000 - 192.1.2.2 192.1.2.255


 link link2 /dev/udp - udp 50001 - 192.1.3.2 192.1.3.255

Sample configuration: Links crossing IP routers

The following illustration depicts a typical configuration of links crossing an IP router employing LLT over UDP. The illustration shows just two nodes of a four-node cluster.

Click the thumbnail above to view full-sized image.

The configuration represented by the following /etc/llttab file for Node 1 has links crossing IP routers. Notice that IP addresses are shown for each link on each peer node. In this configuration broadcasts are disabled. Hence, the broadcast address does not need to be set in the in the link command of the
/etc/llttab file.

set-node Node1

set-cluster 1

link link1 /dev/udp - udp 50000 - 192.1.3.1 -

link link2 /dev/udp - udp 50001 - 192.1.4.1 -

#set address of each link for all peer nodes in the cluster

#format: set-addr <node-id> <link tag-name> <address>

set-addr 0 link1 192.1.1.1

set-addr 0 link2 192.1.2.1

set-addr 2 link1 192.1.5.2

set-addr 2 link2 192.1.6.2

set-addr 3 link1 192.1.7.3

set-addr 3 link2 192.1.8.3

#disable LLT broadcasts

set-bcasthb 0

set-arp 0

The /etc/llttab file on Node 0 would resemble:

set-node Node0

set-cluster 1

link link1 /dev/udp - udp 50000 - 192.1.1.1 -

link link2 /dev/udp - udp 50001 - 192.1.2.1 -

#set address of each link for all peer nodes in the cluster

#format: set-addr <node-id> <link tag-name> <address>

set-addr 1 link1 192.1.3.1

set-addr 1 link2 192.1.4.1

set-addr 2 link1 192.1.5.2

set-addr 2 link2 192.1.6.2

set-addr 3 link1 192.1.7.3

set-addr 3 link2 192.1.8.3

#disable LLT broadcasts

set-bcasthb 0

set-arp 0


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