hold-queue 75 in command

[mjb22]

Hello

Could anyone tell me what the following command means please.

hold-queue 75 in command

And if I don't have this command in my ISDN interface setup on my Cisco router, would this prevent the ISDN backup launching once I loose connectivity to the serial line ?

Thanks

 

[cryptomap]

This is straight off the Cisco site.

Input Queue Overflow
Each interface owns an input queue onto which incoming packets are placed to await processing by the Routing Processor (RP). Frequently, the rate of incoming packets placed on the input queue exceeds the rate at which the RP can process the packets.

Each input queue has a size that indicates the maximum number of packets that may be placed on the queue. Once the input queue becomes full (meaning, the maximum number of packets is on queue), the interface drops additional incoming packets.

The interface enters a throttling mode in which incoming packets are not accepted. The throttling period allows the RP to process the backlog of packets on the input queue. The input queue overflow scenario occurs most often when a higher speed interface is feeding packets to a lower speed interface. An example is shown below.

packetsIn--> 1.5Mb --> Router --> 9.6Kb -->packetsOut

Note: This situation may become more problematic when using Cisco Systems Network Architecture (SNA) because of the high-speed Channel Interface Processor (CIP) versus the lower speeds of the other interfaces.

The following show interface interface-identifier output shows the current output queue levels and the number of outgoing packets dropped:

dspu-7k#show interface channel 4/2

Channel4/2 is up, line protocol is up
Hardware is cxBus IBM Channel
MTU 4472 bytes, BW 98304 Kbit, DLY 100 usec, rely 255/255, load 1/255
Encapsulation CHANNEL, loopback not set, keepalive not set
Virtual interface
Last input 0:00:04, output 0:00:04, output hang never
Last clearing of "show interface" counters never
Output queue 0/40, 0 drops; input queue 63/75, 118 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
101646 packets input, 2427760 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
210328 packets output, 5016959 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets, 0 restarts
0 output buffer failures, 0 output buffers swapped out
The show interface interface-identifier provides the following information:

The input queue x/y counter shows the current number of packets on the input queue x and the current size of the input queue y.

The drops counter indicates the number of incoming packets dropped.

If the current number of packets on the input queue is consistently at or greater than 80 percent of the current size of the input queue, the size of the input queue may require tuning to accommodate the incoming packet rate.

Even if the current number of packets on the input queue never seems to approach the size of the input queue, bursts of packets may still be overflowing the queue.

If the drops counter is increasing at a high rate, the size of the input queue may require tuning to accommodate the bursts.

Note: You can tune the size of the input queue using the hold-queue interface configuration command, as shown in the example below.

interface channel 4/2
hold-queue 125 in


Hope it helps.

 

[routerman]

>And if I don't have this command in my ISDN interface setup on my Cisco router, would this prevent the ISDN backup launching once I loose connectivity to the serial line ?

No, thats a config error that prevents the ISDN kicking in.