Ethernet Speed mistmach between two devices.

[evg.eff@yandex.ru]

Hi Everyone,

2911 router is directly connected to provider switch.

Provider limits the speed of its port to twenty megabits (for example by bandwidth control function)

Interface on 2911 is monitored by Zabbix (in/out octets).

Zabbix loading schedule for the port shows a load of no more than twenty megabits.

Flow control not used.

how to explain this behavior?

[Georg Pauwen]

Hello,

odd. Can you post the output of 'show interfaces x' of the interface in question ? Who is your ISP ?

[evg.eff@yandex.ru]

 MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 7/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full Duplex, 100Mbps, media type is RJ45
  output flow-control is unsupported, input flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:02, 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: fifo
  Output queue: 0/40 (size/max)
  30 second input rate 3091000 bits/sec, 415 packets/sec
  30 second output rate 782000 bits/sec, 460 packets/sec
     3442401307 packets input, 49081606 bytes, 0 no buffer
     Received 154 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     3821223882 packets output, 4040473329 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

[Joseph W. Doherty]

Could you clarify your question? It appears you're asking the provider rate controls traffic to 20 Mbps, and that's what stats show is obtained. If so, what are you asking?

[evg.eff@yandex.ru]

why the port(on my router) load(by zabbix monitoring) does not go higher 20mb? router port speed does no limits

I assume that this is due to the operation of the tcp protocol. I'm right?

[paul driver]

Hello

---

evg.eff@yandex.ru wrote:

why the port(on my router) load(by zabbix monitoring) does not go higher 20mb? router port speed does no limits

I assume that this is due to the operation of the tcp protocol. I'm right?

---

I could be mistaken here but your router ports are connected to a switch that polices its ports to 20mb correct ?

[evg.eff@yandex.ru]

Yes

 Router 2911 interface(no limit)-----(100mb link)------(bandwidth limit 20mb) IPS Switch

[Georg Pauwen]

Hello,

how do you have Zabbix configured ? Are you using a template (such as the one linked below) ?

https://share.zabbix.com/network_devices/cisco/cisco-total

[evg.eff@yandex.ru]

zabbix monitored utilization of router interface by:

ififOctets

ifOutOctets

[Joseph W. Doherty]

If your ISP is rate limiting, TCP will normally rate adapt itself. BTW, some UDP applications will rate adapt too. Those that don't, should allow you to transmit more than 20 Mbps (of course, unlike the other side will obtain higher rate). Also even for those that don't, you shouldn't be able to receive more than 20 Mbps.

[evg.eff@yandex.ru]

I think that I was see more than 20 mb utilization of my router port , because its speed is not limited

[evg.eff@yandex.ru]

"some UDP applications will rate adapt too."

can be more in detail please? 

[Joseph W. Doherty]

Some UDP applications perform some L4 functions provided by TCP. Remember TCP is used so applications, themselves, don't need to directly support logic that's often desired, such as guaranteed delivery, guaranteed sequencing and bandwidth usage.

Reasons vary why applications would not use TCP yet implement TCP like features. For example, in a video stream, video applications often do not want to re-transmit lost packets, but they may shift to a lower quality, and less bandwidth consuming, CODEC if they detect packet loss.

Or consider tftp, it will detect packet loss and retransmit.