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Troubleshooting: Etherchannel

A maioria dos problemas com etherchannel (link aggregation) é causada por erros de configuração. É sempre importante mencionar que a configuração de todas as interfaces físicas deve ser a mesma. Neste texto, veremos alguns dos problemas mais comuns.

Usaremos a seguinte topologia.


Um etherchannel foi configurado para agrupar as interfaces FastEthernet 0/23 e 0/24, mas a configuração não está funcionando. Vamos ao primeiro problema...

Protocolos etherchannel diferentes

O etherchannel não está funcionando. Em primeiro lugar, vamos verificar se as interfaces físicas estão OK:

SW1#show interfaces FastEthernet0/23 | include line protocol
FastEthernet0/23 is up, line protocol is up (connected)
SW1#show interfaces FastEthernet0/24 | include line protocol
FastEthernet0/24 is up, line protocol is up (connected)
SW2#show interfaces FastEthernet0/23 | include line protocol
FastEthernet0/23 is up, line protocol is up (connected)
SW2#show interfaces FastEthernet0/24 | include line protocol
FastEthernet0/24 is up, line protocol is up (connected)

Todas as interfaces estão operacionais. Vamos verificar se há algum problema nas interfaces Port-channel:

SW1#show ip interface brief | include Port
Port-channel1          unassigned      YES unset  down                  down
SW2#show ip interface brief | include Port
Port-channel1          unassigned      YES unset  down                  down

Podemos ver que as interfaces Port-channel foram criadas, mas estão down. Vamos dar uma olhada no etherchannel:

SW1#show etherchannel summary | begin Group
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         LACP      Fa0/23(s)    Fa0/24(s)
SW2#show etherchannel summary | begin Group
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         PAgP      Fa0/23(I)    Fa0/24(I)

Temos aqui um bom comando para verificar o etherchannel. Usamos o show etherchannel summary para visualizar os port-channels. Podemos ver que SW1 foi configurado com LACP e SW2 com PAgP. Isso nunca funcionará. Vamos olhar mais de perto:

SW1#show etherchannel 1 detail
Group state = L2
Ports: 2   Maxports = 16
Port-channels: 1 Max Port-channels = 16
Protocol:   LACP
Minimum Links: 0


                Ports in the group:
                -------------------
Port: Fa0/23
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Active          Gcchange = -
Port-channel  = null        GC   =   -             Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   LACP

Flags:  S - Device is sending Slow LACPDUs   F - Device is sending fast LACPDUs.
        A - Device is in active mode.        P - Device is in passive mode.

Local information:
                            LACP port     Admin     Oper    Port        Port
Port      Flags   State     Priority      Key       Key     Number      State
Fa0/23    SA      susp      32768         0x1       0x1     0x1         0x7D

Age of the port in the current state: 0d:00h:12m:16s

Port: Fa0/24
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Active          Gcchange = -
Port-channel  = null        GC   =   -             Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   LACP

Flags:  S - Device is sending Slow LACPDUs   F - Device is sending fast LACPDUs.
        A - Device is in active mode.        P - Device is in passive mode.

Local information:
                            LACP port     Admin     Oper    Port        Port
Port      Flags   State     Priority      Key       Key     Number      State
Fa0/24    SA      susp      32768         0x1       0x1     0x2         0x7D

Age of the port in the current state: 0d:00h:12m:03s

                Port-channels in the group:
                ---------------------------

Port-channel: Po1    (Primary Aggregator)

------------

Age of the Port-channel   = 0d:00h:12m:16s
Logical slot/port   = 2/1           Number of ports = 0
HotStandBy port = null
Port state          = Port-channel Ag-Not-Inuse
Protocol            =   LACP
Port security       = Disabled

O comando show etherchannel detail é excelente. Ele nos fornece muitas informações, mas estamos particularmente interessados em saber se o LACP está configurado no modo passive ou active. Interfaces em modo active tentarão ativamente formar um etherchannel. Interfaces em modo passive apenas responderão às solicitações do LACP. Vamos dar uma olhada em SW2:

SW2#show etherchannel 1 detail
Group state = L2
Ports: 2   Maxports = 8
Port-channels: 1 Max Port-channels = 1
Protocol:   PAgP
Minimum Links: 0


                Ports in the group:
                -------------------
Port: Fa0/23
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Desirable-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/23          U4/S4   H       30s      0        128        Any      1

Age of the port in the current state: 0d:00h:23m:09s

Port: Fa0/24
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Desirable-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/24          U4/S4   H       30s      0        128        Any      2

Age of the port in the current state: 0d:00h:23m:08s

                Port-channels in the group:
                ---------------------------

Port-channel: Po1
------------

Age of the Port-channel   = 0d:00h:23m:18s
Logical slot/port   = 2/1           Number of ports = 0
GC                  = 0x00000000      HotStandBy port = null
Port state          = Port-channel Ag-Not-Inuse
Protocol            =   PAgP
Port security       = Disabled

O output acima nos mostra que SW2 foi configurado com PAgP e que as interfaces estão no modo desirable. Se elas tivessem sido configuradas no modo auto, estaríamos vendo a flag A. Vamos reconfigurar SW2 com LACP:

SW2(config)#no interface Port-channel1
SW2(config)#
%LINK-5-CHANGED: Interface FastEthernet0/23, changed state to administratively down
%LINK-5-CHANGED: Interface FastEthernet0/24, changed state to administratively down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Interface FastEthernet0/23, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface Interface FastEthernet0/24, changed state to down
SW2(config)#
SW2(config)#interface FastEthernet0/23
SW2(config-if)#channel-group 1 mode passive
Creating a port-channel interface Port-channel 1

SW2(config-if)#
SW2(config-if)#no shutdown
%LINK-3-UPDOWN: Interface FastEthernet0/23, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/23, changed state to up
SW2(config-if)#
SW2(config-if)#interface FastEthernet0/24
SW2(config-if)#channel-group 1 mode passive
SW2(config-if)#no shutdown
%LINK-3-UPDOWN: Interface FastEthernet0/24, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to up

Antes de tudo excluímos a interface Port-channel. Se não fizéssemos isso, o switch mostraria uma mensagem de erro ao tentarmos alterar o modo do channel-group nas interfaces. Depois de alguns segundos veremos que as interfaces Port-channel ficaram up:

SW1 %LINK-3-UPDOWN: Interface Port-channel1, changed state to up
SW2 %LINK-3-UPDOWN: Interface Port-channel1, changed state to up

Após a mudança de configuração, as interfaces Port-channel 1 ficaram up. Problema resolvido!

Certifique-se de usar o mesmo protocolo etherchannel (PAgP ou LACP) nos dois lados.

Negociação PAgP/LACP não funciona

Mesma topologia, problema diferente:


Mais uma vez as interfaces Port-channel estão down:

SW1#show ip interface brief | include Port
Port-channel1          unassigned      YES unset  down                  down
SW2#show ip interface brief | include Port
Port-channel1          unassigned      YES unset  down                  down

As interfaces Port-channel foram criadas, mas estão down em ambos os lados. Vamos dar uma olhada na configuração do etherchannel:

SW1#show etherchannel 1 summary | begin Group
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         PAgP      Et0/0(I)    Et0/1(I)
SW2#show etherchannel 1 summary | begin Group
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         PAgP      Et0/0(I)    Et0/1(I)

Podemos ver que as interfaces FastEthernet 0/23 e 0/24 foram adicionadas ao port-channel. PAgP é o protocolo usado.

SW1#show ip interface brief | begin FastEthernet0/23
FastEthernet0/23       unassigned      YES unset  up                    up      
FastEthernet0/24       unassigned      YES unset  up                    up
SW2#show ip interface brief | begin FastEthernet0/23
FastEthernet0/23       unassigned      YES unset  up                    up      
FastEthernet0/24       unassigned      YES unset  up                    up

As interfaces FastEthernet estão OK, então sabemos que o problema não está com elas. Vamos olhar a configuração do etherchannel com mais detalhes:

SW1#show etherchannel 1 port
                Ports in the group:
                -------------------
Port: Fa0/23
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Automatic-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/23    A     U2/S4           1s       0        128        Any      1

Age of the port in the current state: 0d:00h:08m:50s

Port: Fa0/24
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Automatic-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/24    A     U2/S4           1s       0        128        Any      2

Age of the port in the current state: 0d:00h:08m:49s

Podemos ver que as interfaces FastEthernet 0/23 e 0/24 de SW1 estão configuradas no modo PAgP auto (por causa da flag A). E quanto a SW2?

SW2#show etherchannel 1 port
                Ports in the group:
                -------------------
Port: Fa0/23
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Automatic-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/23    A     U2/S4           1s       0        128        Any      1

Age of the port in the current state: 0d:00h:11m:37s

Port: Fa0/24
------------

Port state    = Up Sngl-port-Bndl Mstr Not-in-Bndl
Channel group = 1           Mode = Automatic-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/24    A     U2/S4           1s       0        128        Any      2

Age of the port in the current state: 0d:00h:11m:38s

As interfaces FastEthernet 0/23 e 0/24 de SW2 também estão configuradas no modo PAgP auto. Isso nunca funcionará porque ambos os switches estão esperando passivamente por mensagens PAgP. Vamos mudar as interfaces de SW2 para o modo desirable:

SW2(config)#interface FastEthernet0/23
SW2(config-if)#channel-group 1 mode desirable 
SW2(config-if)#interface FastEthernet0/24
SW2(config-if)#channel-group 1 mode desirable

SW2 agora pode enviar ativamente mensagens PAgP para SW1, possibilitando assim a negociação do port-channel:

SW1 %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up
SW2 %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up

O etherchannel agora está funcionando. Problema resolvido!

Ao usar PAgP, certifique-se de que pelo menos um dos switches esteja usando o modo desirable. No caso do LACP, pelo menos um dos switches deve estar no modo active.

Incompatibilidade na configuração das interfaces

Mais um problema, com a mesma topologia:


Um etherchannel está configurado entre SW1 e SW2, mas foram reportadas lentidões no link. O que poderia estar errado?

SW1#show ip interface brief | include Port
Port-channel1          unassigned      YES unset  up                    up
SW2#show ip interface brief | include Port
Port-channel1          unassigned      YES unset  up                    up

Uma verificação rápida nos diz que as interfaces Port-channel estão operacionais. Vamos aos detalhes:

SW1#show etherchannel 1 detail 
Group state = L2 
Ports: 2   Maxports = 8
Port-channels: 1 Max Port-channels = 1
Protocol:   PAgP
Minimum Links: 0
  Ports in the group:
  -------------------
Port: Fa0/23
------------

Port state    = Up Cnt-bndl Suspend Not-in-Bndl 
Channel group = 1           Mode = Automatic-Sl    Gcchange = 0
Port-channel  = null        GC   = 0x00000000      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/23    dA U1/S1    1s  0        128        Any      0

Age of the port in the current state: 0d:01h:10m:37s

Probable reason: speed of Fa0/23 is 100M, Fa0/24 is 10M
Port: Fa0/24
------------

Port state    = Up Mstr In-Bndl 
Channel group = 1           Mode = Automatic-Sl    Gcchange = 0
Port-channel  = Po1         GC   = 0x00010001      Pseudo port-channel = Po1
Port index    = 0           Load = 0x00            Protocol =   PAgP

Flags:  S - Device is sending Slow hello.  C - Device is in Consistent state.
        A - Device is in Auto mode.        P - Device learns on physical port.
        d - PAgP is down.
Timers: H - Hello timer is running.        Q - Quit timer is running.
        S - Switching timer is running.    I - Interface timer is running.

Local information:
                                Hello    Partner  PAgP     Learning  Group
Port      Flags State   Timers  Interval Count   Priority   Method  Ifindex
Fa0/24    SAC U6/S7   HQ 30s  1        128        Any      5001

Partner's information:

          Partner              Partner          Partner         Partner Group
Port      Name                 Device ID        Port       Age  Flags   Cap.
Fa0/24    SW2                  0019.569d.5700 Fa0/24      15s SC 10001 

Age of the port in the current state: 0d:00h:04m:29s

  Port-channels in the group: 
  ---------------------------

Port-channel: Po1
------------

Age of the Port-channel   = 0d:01h:30m:23s
Logical slot/port   = 2/1          Number of ports = 1
GC                  = 0x00010001      HotStandBy port = null
Port state          = Port-channel Ag-Inuse 
Protocol            =   PAgP
Port security       = Disabled

Ports in the Port-channel: 

Index   Load   Port     EC state        No of bits
------+------+------+------------------+-----------
  0     00     Fa0/24   Automatic-Sl       0

Time since last port bundled:    0d:00h:04m:31s    Fa0/24
Time since last port Un-bundled: 0d:00h:08m:12s    Fa0/24

Apesar do extenso output do comando show etherchannel detail, podemos ver o que está acontecendo. As interfaces FastEthernet 0/23 e 0/24 foram configuradas para o port-channel, mas o switch não conseguiu agrupá-las porque a interface FastEthernet0/24 está configurada em 10 Mbps. SW2 nos diz a mesma coisa:

SW2#show etherchannel 1 detail | include reason
Probable reason: speed of Fa0/23 is 100M, Fa0/24 is 10M

Aqui está uma boa razão para usarmos o operador include dos comandos show. Estamos interessados apenas na "Probable reason" que o output do show etherchannel detail reproduz.

Vamos alterar o speed da interface FastEthernet0/24 em ambos os switches:

SW1(config)#interface FastEthernet0/24
SW1(config-if)#speed auto
SW2(config)#interface FastEthernet0/24
SW2(config-if)#speed auto

Precisamos garantir que as interfaces FastEthernet 0/23 e 0/24 estão agora com a mesma configuração. Vale a pena dar um show running-config para verificar se elas estão idênticas.

Assim que o speed da interface FastEthernet0/24 for mudado, veremos o etherchannel ficar down e up novamente:

SW1 %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to down
%LINK-3-UPDOWN: Interface Port-channel1, changed state to down
%LINK-3-UPDOWN: Interface Port-channel1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up
SW2 %LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to down
%LINK-3-UPDOWN: Interface Port-channel1, changed state to down
%LINK-3-UPDOWN: Interface Port-channel1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Port-channel1, changed state to up

Agora podemos ver se as duas interfaces foram agrupadas:

SW1#show etherchannel 1 summary | begin Group
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)         PAgP      Fa0/13(P)   Fa0/14(P)
SW2#show etherchannel 1 summary | begin Group
Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)         PAgP      Fa0/13(P)   Fa0/14(P)

Pronto, ambas as interfaces foram adicionadas ao port-channel. Problema resolvido!

Certifique-se de que todas as interfaces do etherchannel estão configuradas exatamente da mesma forma.

Esses são os problemas mais comuns com o etherchannel. O mais rotineiro é o da incompatibilidade na configuração das interfaces físicas. Do mais, nunca se esqueça de que, tanto no PAgP quanto no LACP, pelo menos um dos switches deve estar configurado para negociar o port-channel ativamente.

Hope this helps!

Troubleshooting: Etherchannel Reviewed by Carlos Wolkartt on dezembro 30, 2018 Rating: 5
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