Metric mismatch in Eigrp

[Sanjib Pradhan]

Please someone help me to calculate metric in Eigrp. Please find below Bandwidth and Delay.

R2#sh int s0/1

Serial0/1 is up, line protocol is up

  Hardware is GT96K Serial

  Internet address is 20.1.1.2/24

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

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

  Encapsulation HDLC, loopback not set

  Keepalive set (10 sec)

  CRC checking enabled

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

  Last clearing of "show interface" counters never

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

  Queueing strategy: weighted fair

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

     Conversations  0/1/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1158 kilobits/sec

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

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

     1183 packets input, 77832 bytes, 0 no buffer

     Received 425 broadcasts, 0 runts, 0 giants, 0 throttles

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

     1158 packets output, 76032 bytes, 0 underruns

     0 output errors, 0 collisions, 6 interface resets

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

R2#sh ip route | in 2.2.2.0

D       2.2.2.0 [90/2297856] via 20.1.1.1, 00:59:26, Serial0/1

Metric calculation of EIGRP:

[(10,000,000 / 1544) +2000 ] * 256 =(6476+2000)*256=8476*256=2169856

This value is mismathed with EIGRP calculated metric(i.e 2297856). Please someone figerout if some thing I have missed during calculation.

[Sandeep Choudhary · Accepted solution]

HI Sanjib,

Metric = 256*[10^7/BW(min)] + [sum of delay]/10

Metric = 256*[10^7/1544] + (20000+5000)/10]

Metric = 256*[6476+2500]

Metric = 2297856

• We see the minumum bandwidth to reach the destination  is 1544Kbps
• Default delay on the link to reach the destination (serial link) is 20000 microseconds.
• Default delay of the loopback interface is 5000 microseconds.

Regards

Dont forget to rate helpful posts.

[Peter Paluch · Accepted solution]

Sanjib,

The 2.2.2.0/24 network is on the loopback on R3, right? In that case, you would need to take the loopback's bandwidth and delay into account as well. By default, loopback BW is set to 8 Gbps (more than the serial link's) and delay is 5000 usec, so the resulting metric would be

[(10,000,000 / 1544) + 2500 ] * 256 = 2297856

which matches the show ip route output.

Best regards,

Peter

[Sanjib Pradhan]

Thank you so much Mr. Sandeep and Peter.....