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LAG bandwidth lower than expected

rosscommerce
Level 1
Level 1

Hi, I am trying to configure LAG between SG-250-08 and C3560CG-8PC with the following topography:

 +----+   +----+
 |SRV1|   |SRV2|
 +--+-+   +-+--+
GbE |       | GbE
    |       |
 +--+-------+--+
 | C3560CG-8PC |
 +-----+-+-----+
       | | 2xGbE LAG
       | |
 +-----+-+-----+
 |  SG-250-08  |
 +--+--------+-+
GbE |        | GbE
    |        |
 +--+-+   +--+-+
 | PC1|   |PC2 |
 +----+   +----+   

The Cisco devices are connected with two cat6e cables, both devices have LAG configured and enabled, so the resulting channel should have a total bandwidth of 2Gbit.

I am testing the bandwidth between the following pairs using iperf: PC1 <=> SRV1 and PC2 <=> SRV2

According to my understanding of LAG, I should be able to see 1Gb between each pair.

Instead I see both pairs sharing 1Gb (500/500 Mbit roughly).

Here's the config for C3560CG-8PC

 

interface GigabitEthernet0/1
switchport mode access
switchport access vlan 1
channel-group 1 mode active
!
interface GigabitEthernet0/2
switchport mode access
switchport access vlan 1
channel-group 1 mode active
!
interface Port-Channel1
description UPLINK
port-channel load-balance src-dst-mac

 

Port channel info

 

show interface po1
Port-channel1 is up, line protocol is up (connected)
  Hardware is EtherChannel, address is 80e8.6fe6.2d81 (bia 80e8.6fe6.2d81)
  Description: UPLINK
  MTU 1500 bytes, BW 2000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 7/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, link type is auto, media type is unknown
  input flow-control is off, output flow-control is unsupported
  Members in this channel: Gi0/1 Gi0/2
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:01, output 00:03:17, 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)
  5 minute input rate 56896000 bits/sec, 4682 packets/sec
  5 minute output rate 293000 bits/sec, 527 packets/sec
     2121328 packets input, 3219002211 bytes, 0 no buffer
     Received 242 broadcasts (236 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 236 multicast, 0 pause input
     0 input packets with dribble condition detected
     240329 packets output, 16977081 bytes, 0 underruns
     0 output errors, 0 collisions, 1 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

show etherchannel load-balance
EtherChannel Load-Balancing Configuration:
src-dst-mac
show lacp nei
Flags: S - Device is requesting Slow LACPDUs
F - Device is requesting Fast LACPDUs
A - Device is in Active mode P - Device is in Passive mode

Channel group 1 neighbors

Partner's information:

LACP port Admin Oper Port Port
Port Flags Priority Dev ID Age key Key Number State
Gi0/1 SA 1 a4b4.39bc.dde5 13s 0x0 0x3E8 0x8 0x3D
Gi0/2 SA 1 a4b4.39bc.dde5 23s 0x0 0x3E8 0x7 0x3D

And for SG-250-08

 

interface GigabitEthernet7
channel-group 1 mode auto
!
interface GigabitEthernet8
channel-group 1 mode auto
!
interface Port-Channel1
flowcontrol on
description UPLINK
port-channel load-balance src-dst-mac

Port channel info

#show interface po1

Load balancing: src-dst-mac.

Gathering information...
Channel  Ports
-------  -----
Po1      Active: gi7-8

I tried with LACP enabled/disabled, same result.

When testing I see the LEDs on both ports blinking.

I just don't understand what I am doing wrong.

 

1 Accepted Solution

Accepted Solutions

rosscommerce
Level 1
Level 1

Found my problem - it's called too many open consoles and  working after midnight. Instead of testing PC1-SRV1 and PC2-SRV2 I was testing from the same PC1 against SRV1 and SRV2 from two different consoles which lead to false measurements.

View solution in original post

3 Replies 3

balaji.bandi
Hall of Fame
Hall of Fame

Nothing wrong here in the config ?  But Load sharing based on the src-dest mac algorithm - you can find here:

https://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/12023-4.html

 

Good post and explained here :

https://community.cisco.com/t5/switching/lag-speed-is-not-as-expected/m-p/2689038

 

Anothere test you can do is, what is the speeds SRV1 to SERV2 ? what is the speeds to PC1 to PC2 ?

 

BB

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rosscommerce
Level 1
Level 1

Found my problem - it's called too many open consoles and  working after midnight. Instead of testing PC1-SRV1 and PC2-SRV2 I was testing from the same PC1 against SRV1 and SRV2 from two different consoles which lead to false measurements.

Nice to know are you able to figureout the issue.

BB

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