System information

Troubleshooting Using the show interfaces serial Command
Book Title
15-318
Possible Problem Solution
Input rate to serial interface exceeds
bandwidth available on serial link
Step 1 Minimize periodic broadcast traffic such as routing and SAP
1
updates by using access lists or by other means. For example, to
increase the delay between SAP updates, use the ipx sap-interval
interface configuration command.
Step 2 Increase the output hold queue size in small increments (for instance,
25 percent), using the hold-queue out interface configuration
command.
Step 3 On affected interfaces, turn off fast switching for heavily used
protocols. For example, to turn off IP fast switching, enter the no ip
route-cache interface configuration command. For the command
syntax for other protocols, consult the Cisco IOS configuration
guides and command references.
Step 4 Implement priority queuing on slower serial links by configuring
priority lists. For information on config- uring priority lists, see the
Cisco IOS configuration guides and command references.
Note: Output drops are acceptable under certain conditions. For
instance, if a link is known to be overused (with no way to remedy
the situation), it is often considered preferable to drop packets than
to hold them. This is true for protocols that support flow control and
can retransmit data (such as TCP/IP and Novell IPX
2
). However,
some protocols, such as DECnet and local-area transport are
sensitive to dropped packets and accommodate retransmission
poorly, if at all.
1 SAP = Service Advertising Protocol
2 IPX = Internetwork Packet Exchange