Notas ICMP Router Discovery Messages (IRDP)

Um dos protocolos First Hop Redundancy Protocols (FHRP) é o ICMP Router Discovery Messages (IRDP). Os hosts escolhem o gateway dinamicamente com base nas mensagens advertidas pelos routers e na preferência escolhem o gateway.



  • By default usa advertisements broadcast, em multicast utiliza o IP
  • A preferência + alta prevalece



R4-|                |
—-|switch_L2|-R3R2-|                |

interface FastEthernet0/1
ip address
 ip irdp
 ip irdp address 400
ip irdp preference 40

interface FastEthernet0/1
ip address
 ip irdp
 ip irdp address 350
ip irdp preference 200

R2(config)#ip gdp irdp
%Cannot start GDP client; system is routing IP


!O GDP (Router discovery mechanism) deve ser apenas ativado no host, activar o !multicast caso os advertisiments tambem sejam

ip gdp irdp

interface FastEthernet0/0
ip address
 ip irdp

R3#sh ip route
Gateway         Using  Interval  Priority   Interface    IRDP      824       40        FastEthernet0/0  IRDP      755     350     FastEthernet0/0    IRDP      858       200     FastEthernet0/0

Default gateway is

Notas: A decisão do router eleito como gateway, é sempre feita com base na preference atribuída caso seja configurada. Caso contrário na preference do proxy-advertise.


RFC 1256 – ICMP Router Discovery Messages

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