The following example shows single-topology mode being enabled. An IS-IS instance is created, the NET is defined, IPv6 is configured along with IPv4 on an interface, and IPv4 link topology is used for IPv6.

This configuration allows POS interface 0/3/0/0 to form adjacencies for both IPv4 and IPv6 addresses.

  router isis isp
   net 49.0000.0000.0001.00
   address-family ipv6 unicast
    single-topology
   interface POS0/3/0/0
    address-family ipv4 unicast
    !
    address-family ipv6 unicast
    !
    exit
  !
  interface POS0/3/0/0
   ipv4 address 10.0.1.3 255.255.255.0
   ipv6 address 2001::1/64
  

The following example shows multitopology IS-IS being configured in IPv6.

  router isis isp
   net 49.0000.0000.0001.00
   interface POS0/3/0/0
    address-family ipv6 unicast
    metric-style wide level 1
    exit
  !
  interface POS0/3/0/0
   ipv6 address 2001::1/64
  

The following example shows usage of the attached-bit send always-set and redistribute commands. Two instances, instance “1” restricted to Level 1 and instance “2” restricted to Level 2, are configured.

The Level 1 instance is propagating routes to the Level 2 instance using redistribution. Note that the administrative distance is explicitly configured higher on the Level 2 instance to ensure that Level 1 routes are preferred.

Attached bit is being set for the Level 1 instance since it is redistributing routes into the Level 2 instance. Therefore, instance “1” is a suitable candidate to get from the area to the backbone.

  router isis 1
    is-type level-2-only
   net 49.0001.0001.0001.0001.00
   address-family ipv4 unicast
    distance 116
    redistribute isis 2 level 2
  !
  interface GigabitEthernet 0/3/0/0
   address-family ipv4 unicast
  !
  !
  router isis 2
   is-type level-1
   net 49.0002.0001.0001.0002.00
   address-family ipv4 unicast
    
attached-
bit send always-
set
  !
  interface GigabitEthernet 0/1/0/0
   address-family ipv4 unicast
  

The following example shows how to tag routes.

  route-policy isis-tag-55
  end-policy
  !
  route-policy isis-tag-555
    if destination in (5.5.5.0/24 eq 24) then
      set tag 555
      pass
    else
      drop
    endif
  end-policy
  !
  router static
   address-family ipv4 unicast
    0.0.0.0/0 2.6.0.1
    5.5.5.0/24 Null0
   !
  !
  router isis uut
   net 00.0000.0000.12a5.00
   address-family ipv4 unicast
    metric-style wide
    redistribute static level-1 route-policy isis-tag-555
    spf prefix-priority critical tag 13
    spf prefix-priority high tag 444
    spf prefix-priority medium tag 777
  
  

The following example shows how to activate IS-IS overload bit avoidance:

  config
   mpls traffic-eng path-selection ignore overload

The following example shows how to deactivate IS-IS overload bit avoidance:

  config
   no mpls traffic-eng path-selection ignore overload