Cisco Systems BC-281 SNA Dial-on-Demand Routing, Following command configures the SNA DDR feature

Configuring Data-Link Switching Plus

DLSw+ Configuration Task List

SNA Dial-on-Demand Routing

This feature allows you to run DLSw+ over a switched line and have the Cisco IOS software take the switched line down dynamically when it is not in use. Utilizing this feature gives the IP Routing table more time to converge when a network problem hinders a remote peer connection. In small networks with good IP convergence time and ISDN lines that start quickly, it is not as necessary to use the keepalive option. To use this feature, you must set the keepalive value to zero, and you may need to use a lower value for the timeout option than the default, which is 90 seconds.

To configure SNA DDR, use the following command in global configuration mode:

Command	Purpose
Router(config)# dlsw remote-peer list-numbertcp	Configures SNA DDR.
ip-address [backup-peer[ip-address
frame-relay interface serial number dlci-number
interface name]] [bytes-netbios-out
bytes-list-name][circuit-weightweight]
[cluster cluster-id] [cost cost] [dest-mac
mac-address][dmac-output-list
access-list-number][host-netbios-out
host-list-name] [inactivity] [dynamic]
[keepalive seconds] [lf size] [linger minutes]
[lsap-output-list list] [no-llc minutes]
[passive] [priority] [rif-passthru
virtual-ring-number][tcp-queue-maxsize]
[timeout seconds]

The following command configures the SNA DDR feature:

dlsw remote-peer 0 tcp 10.2.13.4 keepalive 0

UDP Unicast Feature

The UDP Unicast feature sends the SSP address resolution packets via UDP unicast service rather than TCP. (SSP packets include: CANUREACH_EX, NETBIOS_NQ_ex, NETBIOS_ANQ, and DATAFRAME.) The UDP unicast feature allows DLSw+ to better control address resolution packets and unnumbered information frames during periods of congestion. Previously, these frames were carried over TCP. TCP resends frames that get lost or delayed in transit, and hence aggravate congestion. Because address resolution packets and unnumbered information frames are not sent on a reliable transport on the LAN, sending them reliably over the WAN is unnecessary. By using UDP for these frames, DLSw+ minimizes network congestion.

Note UDP unicast enhancement has no affect on DLSw+ FST or direct peer encapsulation.

This feature is enabled by default. To disable User Datagram Protocol (UDP) Unicast, use the following command in global configuration mode:

Command	Purpose
Router(config)# dlsw udp-disable	Disables UDP Unicast.

	Cisco IOS Bridging and IBM Networking Configuration Guide
78-11737-02		BC-301