OS10 Introdução à configuração de MTU

Principais tópicos abordados 

Configuração padrão de MTU

• O valor padrão de MTU é 9.216 bytes a partir da versão 10.5.4.4. Anteriormente, era de 1532 bytes.
• Comandos para configurar e verificar valores de MTU:
  • default mtu <value>: Define um valor de MTU personalizado para todas as interfaces sem uma MTU configurada pelo usuário
  • no default mtu: Redefine as interfaces para o valor de MTU padrão do sistema
  • show default mtu: Exibe a MTU padrão no nível do sistema
  • show interface: Mostra a MTU atual para uma interface específica 

Exemplos de configuração de MTU

• Exemplos de como exibir e modificar a MTU padrão usando comandos da CLI
• Cenários de configuração para LANs virtuais (VLAN) e redes virtuais, destacando a importância de configurações de MTU consistentes em todas as interfaces para evitar falhas de VPN L2 e L3

Considerações e práticas recomendadas

• Garanta configurações uniformes de MTU em todas as interfaces, inclusive interfaces lógicas e físicas entre os pares do protocolo BGP (Border Gateway Protocol)
• A fragmentação não é compatível com a maioria dos switches de energia da Dell, exceto para modelos específicos, como as plataformas Série S4200-ON e S5148-ON
• O OS10 seleciona o menor valor de MTU configurado na VLAN ou nos membros da VLAN para ser a MTU da VLAN

 MTU

• Depois do upgrade para a versão 10.5.4.4, a MTU assume como padrão 9216 todas as VLANs e interfaces Ethernet que ainda não têm uma MTU configurada pelo usuário

Possíveis problemas com a configuração incorreta de MTU 

Perda de pacotes

• Se a MTU for definida como muito baixa, pacotes maiores serão descartados, levando a uma perda significativa de dados e degradação do desempenho da rede 

Abas de rede

• Configurações inconsistentes de MTU entre interfaces podem causar falhas de VPN L2 e L3, interrompendo a estabilidade e a conectividade da rede 

Latência aumentada

• Configurações incorretas de MTU podem levar ao aumento da fragmentação, causando maior latência e menor throughput

Exibe a MTU padrão.

OS10# show default mtu
Default MTU 9216 bytes

Padrão do sistema sem configuração de usuário

OS10# show interface ethernet 1/1/1
Ethernet 1/1/1 is up, line protocol is down
Hardware is Eth, address is 90:b1:00:00:00:a0
 Current address is 90:b1:00:00:00:a0
Pluggable media present, QSFP+ type is QSFP+ 40GBASE-LR4
 Wavelength is 1311
 Receive power reading is no power
Interface index is 11
Internet address is not set
Mode of IPv4 Address Assignment: not set
Interface IPv6 oper status: Disabled
MTU 9216 bytes, IP MTU 1500 bytes
LineSpeed 0, Auto-Negotiation off
Flowcontrol rx off tx off
ARP type: ARPA, ARP Timeout: 60
Last clearing of "show interface" counters: 20:45:24
Queuing strategy: fifo
Input statistics:
 0 packets, 0 octets
 0 64-byte pkts, 0 over 64-byte pkts, 0 over 127-byte pkts
 0 over 255-byte pkts, 0 over 511-byte pkts, 0 over 1023-byte pkts
 0 Multicasts, 0 Broadcasts, 0 Unicasts
 0 runts, 0 giants, 0 throttles
 0 CRC, 0 overrun, 0 discarded
Output statistics:
 0 packets, 0 octets
 0 64-byte pkts, 0 over 64-byte pkts, 0 over 127-byte pkts
 0 over 255-byte pkts, 0 over 511-byte pkts, 0 over 1023-byte pkts
 0 Multicasts, 0 Broadcasts, 0 Unicasts
 0 throttles, 0 discarded, 0 Collisions, wred drops
Rate Info(interval 30 seconds):
 Input 0 Mbits/sec, 0 packets/sec, 0% of line rate
Output 0 Mbits/sec, 0 packets/sec, 0% of line rate
Time since last interface status change: 20:45:25
OS10# configure terminal
OS10(config)# default mtu 9000
OS10(config)#

• Exemplo 

OS10# default mtu 9216
OS10# no default mtu

Tabela 54. Casos de uso da configuração de MTU da VLAN.

Configuração	Configuração da interface Ethernet	Mostrar saída da interface
interface vlan300 no shutdown !	interface ethernet1/1/6 no shutdown switchport mode trunk switchport trunk allowed vlan300 ! interface ethernet1/1/9 no shutdown switchport mode trunk switchport trunk allowed vlan300	OS10# show interface vlan300 Vlan300 is up, line protocol is up Address is 14:10:10:0d:00:e9, Current address is 14:10:10:0d:00:e9 Interface index is 84 Internet address is not set Mode of IPv4 Address Assignment: not set Interface IPv6 oper status: Enabled Link local IPv6 address: fe80::1010:10ff:fe0d:e9/10 MTU 1532 bytes, IP MTU 1500 bytes
interface vlan300 no shutdown !	interface ethernet1/1/6 no shutdown switchport mode trunk switchport trunk allowed vlan300 ! interface ethernet1/1/9 no shutdown switchport mode trunk switchport trunk allowed vlan300 mtu 1312	OS10# show interface vlan300 Vlan300 is up, line protocol is up Address is 14:10:10:0d:00:e9, Current address is 14:10:10:0d:00:e9 Interface index is 84 Internet address is not set Mode of IPv4 Address Assignment: not set Interface IPv6 oper status: Enabled Link local IPv6 address: fe80::1010:10ff:fe0d:e9/10 MTU 1312 bytes, IP MTU 1280 bytes
virtual-network 3333 ! interface vlan300 no shutdown virtual-network 3333 !	interface ethernet1/1/6 no shutdown switchport mode trunk switchport trunk allowed vlan300 ! interface ethernet1/1/9 no shutdown switchport mode trunk switchport trunk allowed vlan300 mtu 1312	OS10# # show interface vlan300 Vlan300 is up, line protocol is up Address is 14:18:77:0d:00:e9, Current address is 14:18:77:0d:00:e9 Interface index is 84 Internet address is not set Mode of IPv4 Address Assignment: not set Interface IPv6 oper status: Enabled Link local IPv6 address: fe80::1618:77ff:fe0d:e9/64 MTU 1532 bytes, IP MTU 1500 bytes
virtual-network 3333 ! interface vlan300 no shutdown virtual-network 3333 ! interface virtual-network 3333	interface ethernet1/1/6 no shutdown switchport mode trunk switchport trunk allowed vlan300 ! interface ethernet1/1/9 no shutdown switchport mode trunk switchport trunk allowed vlan300 mtu 1312	show interface vlan300 Vlan300 is up, line protocol is up Address is 14:18:77:0d:00:e9, Current address is 14:18:77:0d:00:e9 Interface index is 84 Internet address is not set Mode of IPv4 Address Assignment: not set Interface IPv6 oper status: Enabled Link local IPv6 address: fe80::1618:77ff:fe0d:e9/64 MTU 1532 bytes, IP MTU 1500 bytes OS10# show interface virtual-network 3333 Virtual-network 3333 is up, line protocol is up Address is 14:18:77:0d:00:ea, Current address is 14:18:77:0d:00:ea Interface index is 87 Internet address is not set Mode of IPv4 Address Assignment: not set Interface IPv6 oper status: Enabled MTU 1312 bytes, IP MTU 1280 bytes

• Exemplo

OS10(conf-if-eth1/1/7)# mtu 3000

• Exemplo

OS10# show default mtu
Default MTU 9216 bytes