Monitoring Received IPv6 Router Advertisements

Purpose

Display IPv6 router advertisement information received. You can use the conflicts keyword to display router advertisements that differ from the advertisements configured.

Action

To display IPv6 router advertisement information received:

host1#show ipv6 routers
Router FE80::83B3:60A4 on FastEthernet2/0, last update 3 min
  Hops 0, Lifetime 6000 sec, AddrFlag=0, OtherFlag=0
  Reachable time 0 msec, Retransmit time 0 msec
  Prefix 3FFE:C00:8007::800:207C:4E37/96 autoconfig
    Valid lifetime -1, preferred lifetime -1
Router FE80::290:27FF:FE8C:B709 on FastEthernet2/1, last update 0 min
  Hops 64, Lifetime 1800 sec, AddrFlag=0, OtherFlag=0
  Reachable time 0 msec, Retransmit time 0 msec 

To display router advertisements that differ from the advertisements configured:

host1#show ipv6 routers conflicts
Router FE80::203:FDFF:FE34:7039 on FastEthernet1/0, last update 1 min, CONFLICT
   Hops 64, Lifetime 1800 sec, AddrFlag=0, OtherFlag=0
   Reachable time 0 msec, Retransmit time 0 msec
   Prefix 2003::/64 onlink autoconfig
     Valid lifetime -1, preferred lifetime -1

Meaning

Table 45 lists the show ipv6 routers command output fields.

Table 45: show ipv6 routers Output Fields

Field Name

Field Description

Router

Router for which this information applies

Hops

Number of hops that the router uses in router advertisements

Lifetime

Lifetime (in seconds) of the neighbor discovery router advertisement

AddrFlag

State of the neighbor discovery router advertisement managed flag

OtherFlag

State of the neighbor discovery router advertisement other config flag

Reachable time

Amount of time (in milliseconds) that the neighbor is expected to remain reachable

Retransmit time

Interval in which the router retransmits neighbor solicitations

Prefix

IPv6 network number to include in router advertisements

Autoconfig

When present, indicates that local host links use the specified prefix for IPv6 autoconfiguration

Valid lifetime

Amount of time in seconds that the router advertises the IPv6 prefix as valid

preferred lifetime

Amount of time in seconds that the router advertises the specified IPv6 prefix as preferred

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