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what does available bandwidth mean in the "sh int"?

I have a 2660 router with two four port serial network modules. On one the "sh int" looks normal for each interface. The other has an additional line that reports available bandwidth. The display below shows BW 1544 and later available bandwidth 1158. Where does it get that number and what are the implications. Is it showing up because of the generation of network module?

Serial1/1 is up, line protocol is up

Hardware is M4T

MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation FRAME-RELAY, crc 16, loopback not set

Keepalive set (10 sec)

LMI enq sent 11450, LMI stat recvd 11448, LMI upd recvd 0, DTE LMI up

LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0

LMI DLCI 1023 LMI type is CISCO frame relay DTE

FR SVC disabled, LAPF state down

Broadcast queue 0/64, broadcasts sent/dropped 133994/0, interface broadcasts 1


Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 1d07h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 196

Queueing strategy: weighted fair

Output queue: 0/1000/64/196 (size/max total/threshold/drops)

Conversations 0/6/256 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1158 kilobits/sec

5 minute input rate 0 bits/sec, 2 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

367988 packets input, 56694007 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

500568 packets output, 170261120 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions DCD=up DSR=up DTR=up RTS=up CTS=up


Re: what does available bandwidth mean in the "sh int"?

When ever you have a queueing mechanism configured on

an interface, the avaialble bandwidth that is usable by the traffic queue would be 75% of the total bandwdith.

In your case its 75% of 1544 = 1158kb/s.

The remaining 25% is used for router operation and maintanace control

packet e.g routing updates, keepalives etc.

This is normal.