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In a network with multiple capable paths, the DLSw+ Enhanced Load Balancing feature improves traffic load balancing between peers by distributing new circuits based on existing loads and the desired ratio.
For each capable peer (peers that have the lowest or equal cost specified), the DLSw+ Enhanced Load Balancing feature calculates the difference between the desired and the actual ratio of circuits being used on a peer. It detects the path that is underloaded in comparison to the other capable peers and will assign new circuits to that path until the desired ratio is achieved.
When a DLSw+ router is deciding which path to use to start a new circuit, it checks to see what type of load balancing is configured. In Figure 1, assume Router B and Router C have 8 circuits each and then Router B fails. As a result, Router C now has 8 circuits and Router B has 0. When Router B recovers, the recovered 8 circuits will be distributed in the following manner, depending on the type of load balancing that is configured:
If router B is a Cisco 7500 and router C is a Cisco 2500, the user can configure Router B with a circuit weight of 20 and Router C with a circuit weight of 10. In this case, router A knows that router B should be handling twice as many circuits as router C. Router A checks how many circuits it has with each peer and makes its decision based on a 2:1 ratio. The 8 new circuits are distributed to router B and when more circuits are created, all of the new circuits would come up through router B until there is a 2:1 ratio between router B and router C.
If router B fails and then recovers, the first 16 circuits go to router B to achieve the 2:1 balance because router C already has 8 circuits.
Only TCP and DLSw+ Lite encapsulation work with the DLSw+ Enhanced Load Balancing feature.
This feature is supported on the following platforms:
Because a DLSw+ peer selects its new circuit paths from within its reachability cache, the user must configure the dlsw timer explorer-wait-time command with enough time to allow for all the explorer responses to be received. If the new DLSw+ Enhanced Load Balancing Feature is enabled, a message is displayed on the console to alert the user that the timer is not set.
For multiple peer connections, peer costs must be applied. The DLSw+ Enhanced Load Balancing feature works only with the lowest (or equal) cost peers. For example, if the user specifies dlswrtr1, dlswrtr2 and dlswrtr3 with costs of 4, 3, and 3 respectively, DLSw+ establishes new circuits with only dlswrtr 2 and dlswrtr3.
No MIBs are supported by this feature.
This feature supports the following RFCs:
To enable the DLSw+ Enhanced Load Balancing feature on the local router, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
dlsw load-balance [round-robin | circuit count circuit-weight] | Configures the DLSw+ Enhanced Load Balancing feature on the local router. |
To adjust the circuit weight for a remote peer with TCP encapsulation, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
Adjust the circuit weight on the remote peer. |
To adjust the circuit weight for a remote peer with DLSw+ Lite encapsulation, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
dlsw remote-peer frame-relay interface serial number dlci number [circuit-weight value] | Adjust the circuit weight on the remote peer. |
The circuit-weight of a remote peer controls the number of circuits that peer can take. If multiple, equally low-cost peers can reach a remote source, the circuits to that remote source are distributed among the remote peers based on the ratio of their configured circuit-weights. The peer with the highest circuit-weight takes more circuits.
To configure the amount of time needed for all the explorer responses to be received, use the following command in global configuration mode:
| Command | Purpose |
|---|---|
Time to wait for all stations to respond to explorers. |
Figure 2 shows DLSw+ configured with the DLSw+ Enhanced Load Balancing feature.
Router A is configured for the DLSw+ Enhanced Load Balancing feature to load balance traffic among the DLSw+ remote peers B, C, and D.
dlsw local-peer 10.2.19.1 dlsw remote-peer 0 tcp 10.2 24.2 circuit weight 10 dlsw remote-peer 0 tcp 10.2.19.5 circuit weight 6 dlsw remote-peer 0 tcp 10.2.20.1 circuit weight 20 dlsw load-balance circuit-count dlsw timer explorer-wait-time 100
dlsw local-peer 10.2.24.2 cost 1 promiscuous
dlsw local-peer 10.2.19.5 cost 1 promiscuous
dlsw local-peer 10.2.20.1 cost 1 promiscuous
This section documents new or modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.
Use the dlsw load-balance global configuration command to enable load balancing and to select either round robin or circuit-count based load balancing.
dlsw load-balance [round-robin | circuit-count circuit weight]
round-robin | Enables round-robin type of load balancing. |
circuit-count circuit weight | Enables the DLSw+ Enhanced Load Balancing feature. The value represents the default circuit-weight to be used for the peers that are not explicitly configured with a circuit-weight value in the dlsw remote-peer tcp command. The valid range is 1 to 100. |
Fault-tolerant mode is the default setting. The default value for the circuit weight is 10.
Global configuration
This command first appeared in 12.0(3)T.
A circuit is never be taken down and reestablished by the code in an attempt to rebalance the load. The DLSw+ Enhanced Load Balancing feature only changes the decision-making process at the time a new circuit is desired.
The dlsw load-balance command replaces the dlsw duplicate-path-bias load balance command. The latter command continues to be accepted, however, it will be converted to the new command if the configuration is displayed or saved.
The following example enables the DLSw+ Enhanced Load Balancing feature:
dlsw load -balance circuit-count 10
Use the dlsw remote-peer frame-relay global configuration command to specify the remote peer with which the router will connect. Use the no form of this command to disable the previous assignments.
dlsw remote-peer list-number frame-relay interface serial number dlci-number
list-number | Ring list number. The valid range is 1 to 255. The default is 0, which means DLSw+ forwards explorers over all ports or bridge groups on which DLSw+ is enabled. |
interface serial number | Serial interface number of the remote peer with which the router is to communicate. |
dlci-number | DLCI number of the remote peer. |
backup-peer ip-address | (Optional) IP address of the existing TCP/FST peer for which this peer is the backup peer. |
backup-peer frame-relay interface serial number dlci-number | (Optional) Serial interface and DLCI number of the existing Direct/LLC2 Frame-Relay peer for which this peer is the backup peer. |
backup-peer interface name | (Optional) Interface name of the existing direct peer for which this peer is the backup peer. |
bytes-netbios-out bytes-list-name | (Optional) Configures NetBIOS bytes output filtering for this peer. The bytes-list-name argument is the name of the previously defined NetBIOS bytes access list filter. |
circuit weight weight | (Optional) Configures circuit-weight for this remote peer. |
cost cost | (Optional) Cost to reach this remote peer. The valid range is 1 to 5. |
dest-mac mac-address | (Optional) Permits the connection to be established only when there is an explorer frame destined for the specified 48-bit MAC address written in dotted triplet form. |
dmac-output-list access-list-number | (Optional) Establishes the connection only when the explorer frame passes the specified access list. The access-list-number is the list number specified in the access-list command. |
host-netbios-out host-list-name | (Optional) Configures NetBIOS host output filtering for this peer. The host-list-name is the name of the previously defined NetBIOS host access list filter. |
keepalive seconds | (Optional) Sets the keepalive interval for this remote peer. The range is 0 to 1200 seconds. |
lf size | (Optional) Largest frame size, in bytes, this local peer will use on a circuit to avoid segmented frames. Valid sizes are 516, 1470, 1500, 2052, 4472, 8144, 11407, 11454, and 17800 bytes. |
linger minutes | (Optional) Configures length of time the backup peer remains connected after the primary peer connection is reestablished. The valid range is 1 to 300 minutes. The default is 5 minutes. |
lsap-output-list list | (Optional) Filters output IEEE 802.5 encapsulated packets. Valid access list numbers are in the range 200 to 299. |
passive | (Optional) Designates this remote peer as passive. |
pass-thru | Selects passthru mode. The default is local acknowledgment mode. |
No remote peers are specified.
Global configuration
This command first appeared in Cisco IOS Release 11.0. The following keywords and arguments first appeared in Cisco IOS Release 11.2: dest-mac mac-address, dmac-output-list access-list-number, and linger minutes.
The cost keyword specified in a remote peer statement takes precedence over the cost learned as part of the capabilities exchange with the remote peer. The cost keyword is relevant only in fault tolerance mode.
When you need to permit access to only a single MAC address, the dest-mac option is a simpler configuration than the dmac-output-list option.
When pass-thru is not specified, traffic is locally acknowledged and reliably transported in LLC2 across the WAN.
The following example specifies a DLSw+ Lite peer as a backup to a primary direct peer:
dlsw remote-peer 0 frame-relay interface serial 1 40 pass-thru dlsw remote-peer 0 frame-relay interface serial 0 30 backup-peer frame-relay interface serial 1 40
The following example specifies Frame Relay encapsulation connection for remote peer transport:
dlsw remote-peer 0 frame-relay interface 0 30
Use the dlsw remote-peer tcp global configuration command to identify the IP address of a peer with which to exchange traffic using TCP. Use the no form of this command to remove a remote peer.
dlsw remote-peer list-number tcp ip-address [backup-peer [ip-address | frame-relay
list-number | Remote peer ring group list number. This ring group list number default is 0. Otherwise, this value must match the number you specify with the dlsw ring-list, dlsw port-list, or dlsw bgroup-list command. |
tcp ip-address | IP address of the remote peer with which the router is to communicate. |
backup-peer ip-address | (Optional) IP address of the existing TCP/FST peer for which this peer is the backup peer. |
backup-peer frame-relay interface serial number dlci-number | (Optional) Serial interface and DLCI number of the existing Direct/LLC2 Frame Relay peer for which this peer is the backup peer. |
backup-peer interface name | (Optional) Interface name of the existing direct peer for which this peer is the backup peer. |
bytes-netbios-out bytes-list-name | (Optional) Configures NetBIOS bytes output filtering for this peer. The bytes-list-name argument is the name of the previously defined NetBIOS bytes access list filter. |
circuit-weight value | (Optional) Configures the target state that DLSw+ tries to maintain. The valid range is 1 to 100. |
cost cost | (Optional) Cost to reach this remote peer. The valid range is 1 to 5. |
dest-mac mac-address | (Optional) Establishes the TCP connection only when there is an explorer frame destined for the specified 48-bit MAC address written in dotted triplet form. |
dmac-output-list access-list-number | (Optional) Establishes the TCP connection only when the explorer frame passes the specified access list. The access-list-number is the list number specified in an access-list command. |
dynamic | (Optional) Establishes the TCP connection only when there is DLSw+ data to send. |
host-netbios-out host-list-name | (Optional) Configures NetBIOS host output filtering for this peer. The host-list-name is the name of the previously defined NetBIOS host access list filter. |
inactivity minutes | (Optional) Configures the length of time a connection is idle before closing the dynamic remote peer connection. The valid range is 1 to 300 minutes. The default is 5 minutes. |
keepalive seconds | Sets the keepalive interval for this remote peer. The range is 0 to 1200 seconds. |
lf size | (Optional) Largest frame size, in bytes, this local peer uses on a circuit to avoid segmented frames. Valid sizes are 516, 1470, 1500, 2052, 4472, 8144, 11407, 11454, and 17800 bytes. |
linger minutes | (Optional) Configures length of time the backup peer remains connected after the primary peer connection is reestablished. The valid range is 1 to 300 minutes. The default is 5 minutes. |
lsap-output-list list | (Optional) Filters output IEEE 802.5 encapsulated packets. Valid access list numbers are in the range 200 to 299. |
no-llc minutes | (Optional) Configures the length of time a remote peer remains connected after all LLC2 connections are gone. The valid range is 1 to 300 minutes. The default is 5 minutes. |
passive | (Optional) Designates this remote peer as passive. |
priority | (Optional) Enables prioritization features for this remote peer. Valid TCP port numbers are the following: · High: 2065 · Medium: 1981 · Normal: 1982 · Low: 1983 |
rif-passthru virtual-ring-number | (Optional) Configures the remote peer as RIF-Passthru. The virtual-ring-number value is the same number as the ring number value assigned in the source-bridge ring-group commands of the DLSw+ Passthru peers. |
tcp-queue-max size | (Optional) Maximum output TCP queue size for this remote peer. The valid maximum TCP queue size is a number in the range 10 to 2000. |
timeout seconds | (Optional) Configures the retransmit time limit for TCP. The valid range is 5 to 1200 seconds. The default is 90 seconds. |
No peer IP address is identified.
The linger option is inactive. If the linger option is added with no minutes specified, the default is 5 minutes.
The dynamic option is not on by default. If the dynamic option is added without either the inactivity or no-llc argument specified, the default is to terminate the TCP connection to the remote peer after 5 minutes of no active LLC2 connection.
Global configuration
This command first appeared in Cisco IOS Release 10.3. The following keywords and arguments first appeared in Cisco IOS Release 11.1: dynamic, inactivity minutes, linger minutes, no-llc minutes and timeout seconds. The following keywords and arguments first appeared in Cisco IOS Release 11.2: dest-mac mac-address, dmac-output-list access-list-number, linger minutes.
SNA Dial-on-Demand Routing allows switched links to be closed during idle periods. To enable this feature, set the keepalive option to 0 and configure the timeout option. When the dynamic option is configured, the keepalive option is automatically set to 0.
To enhance DDR cost-savings, you can configure the TCP connection to a remote peer to be dynamically established (that is, established only when there is DLSw data to send). You can further configure the TCP connection to terminate after a specified period of idle time on the peer or after a specified period of no active LLC sessions on the peer.
You cannot use both no-llc and inactivity in a command specifying a dynamic peer.
When you need to permit access to a single MAC address, the dest-mac option is a shortcut over the dmac-output-list option.
Use the linger option to specify that a backup peer will remain connected for a specified period of time after the primary connection is gone.
When the priority option on the dlsw remote-peer command is configured, DLSw+ automatically activates four TCP ports to that remote peer (ports 2065, 1981, 1982 and 1983) and assigns traffic to specific ports. Furthermore, if APPN is running with DLSw+ and you specify the priority option on the dlsw remote-peer command, then the SNA TOS maps APPN class COS to TCP TOS and preserves the APPN COS characteristics throughout the network.
The rif passthru option works only on Token Ring LANs via SRB. Other LAN types, such as SDLC and QLLC, are not supported. The RIF Passthru feature is supported with TCP encapsulation and it disables local acknowledgment.
The following features are not supported with the DLSw+ RIF Passthru feature:
The following example specifies a TCP encapsulation connection for remote peer transport:
dlsw remote-peer 0 tcp 10.2.17.8
The following example specifies a TCP peer as backup to a primary FST peer:
dlsw remote-peer 0 fst 10.2.18.9 dlsw remote-peer 0 tcp 10.2.17.8 backup-peer 10.2.18.9
Posted: Thu Feb 25 15:07:33 PST 1999
Copyright 1989-1999©Cisco Systems Inc.