IPv6 IS-IS supports all IPv4 IS-IS features except that it advertises IPv6 routing information. This chapter describes only IPv6 IS-IS specific configuration tasks. For information about IS-IS, see "Configuring IS-IS."

Intermediate System-to-Intermediate System (IS-IS) supports multiple network protocols, including IPv6. To support IPv6, the IETF added two type-length-values (TLVs) and a new network layer protocol identifier (NLPID).

The TLVs are as follows:

· IPv6 Reachability—Contains routing prefix and metric information to describe network reachability and has a type value of 236 (0xEC).

· IPv6 Interface Address—Same as the "IP Interface Address" TLV in IPv4 ISIS, except that the 32-bit IPv4 address is translated to the 128-bit IPv6 address.

The new NLPID is an 8-bit field that identifies which network layer protocol is supported. For IPv6, the NLPID is 142 (0x8E), which must be carried in hello packets sent by IPv6 IS-IS.

Configuring basic IPv6 IS-IS

Before you configure basic IPv6 IS-IS, complete the following tasks:

· Configure IPv6 addresses for interfaces to ensure IPv6 connectivity between neighboring nodes.

· Enable IS-IS.

Basic IPv6 IS-IS configuration can implement the interconnection of IPv6 networks.

To configure basic IPv6 IS-IS:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable an IS-IS process and enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	By default, no IS-IS process is enabled.
3. Configure the network entity title (NET) for the IS-IS process.	network-entity net	By default, no NET is configured.
4. Create the IPv6 address family and enter its view.	address-family ipv6 [ unicast ]	By default, no IS-IS IPv6 address family exists.
5. Return to IS-IS view.	quit	N/A
6. Return to system view.	quit	N/A
7. Enter interface view.	interface interface-type interface-number	N/A
8. Enable IPv6 for IS-IS on the interface.	isis ipv6 enable [ process-id ]	By default, IPv6 is disabled for IS-IS on an interface.

Configuring IPv6 IS-IS route control

Before you configure IPv6 IS-IS route control, complete basic IPv6 IS-IS configuration.

To configure IPv6 IS-IS route control:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Enter IS-IS IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
4. Specify a preference for IPv6 IS-IS routes.	preference { route-policy route-policy-name \| preference } *	By default, the default setting is 15.
5. Configure an IPv6 IS-IS summary route.	summary ipv6-prefix prefix-length [ avoid-feedback \| generate_null0_route \| [ level-1 \| level-1-2 \| level-2 ] \| tag tag ] *	By default, no IPv6 IS-IS summary route is configured.
6. Configure IPv6 IS-IS to advertise a default route.	default-route-advertise [ avoid-learning \| [ level-1 \| level-1-2 \| level-2 ] \| route-policy route-policy-name \| tag tag ] *	By default, IPv6 IS-IS does not advertise Level-1 and Level-2 default routes.
7. Configure IPv6 IS-IS to filter redistributed routes.	filter-policy { ipv6-acl-number \| prefix-list prefix-list-name \| route-policy route-policy-name } export [ protocol [ process-id ] ]	By default, IPv6 IS-IS does not filter redistributed routes. This command is usually used together with the import-route command.
8. Configure IPv6 IS-IS to filter received routes.	filter-policy { ipv6-acl-number \| prefix-list prefix-list-name \| route-policy route-policy-name } import	By default, IPv6 IS-IS does not filter received routes.
9. Configure IPv6 IS-IS to redistribute routes from another routing protocol.	import-route protocol [ as-number \| process-id ] [ allow-ibgp ] [ allow-direct \| cost cost-value \| [ level-1 \| level-1-2 \| level-2 ] \| route-policy route-policy-name \| tag tag ] *	By default, IPv6 IS-IS does not redistribute routes from any other routing protocol.
10. Configure the maximum number of redistributed Level 1/Level 2 IPv6 routes.	import-route limit number	By default, the maximum number of redistributed Level 1/Level 2 IPv6 routes is 1000100.
11. Configure route advertisement from Level-2 to Level-1.	import-route isisv6 level-2 into level-1 [ filter-policy { ipv6-acl-number \| prefix-list prefix-list-name \| route-policy route-policy-name } \| tag tag ] *	By default, IPv6 IS-IS does not advertise routes from Level-2 to Level-1.
12. Configure route advertisement from Level-1 to Level-2.	import-route isisv6 level-1 into level-2 [ filter-policy { ipv6-acl-number \| prefix-list prefix-list-name \| route-policy route-policy-name } \| tag tag ] *	By default, IPv6 IS-IS advertises routes from Level-1 to Level-2.
13. Specify the maximum number of ECMP routes for load balancing.	maximum load-balancing number	By default, the maximum number of ECMP routes is 8.

Configuring IPv6 IS-IS link cost

Configuring an IPv6 IS-IS cost for an interface

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { narrow \| wide \| wide-compatible \| { compatible \| narrow-compatible } [ relax-spf-limit ] }	By default, the IS-IS cost type is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Return to IS-IS view.	quit	N/A
7. Return to system view.	quit	N/A
8. Enter interface view.	interface interface-type interface-number	N/A
9. Enable IPv6 for IS-IS on the interface.	isis ipv6 enable [ process-id ]	By default, IPv6 is disabled for IS-IS on an interface.
10. Specify an IPv6 cost for the IS-IS interface.	isis ipv6 cost cost-value [ level-1 \| level-2 ]	By default, no IPv6 cost is specified for the interface.

Configuring a global IPv6 IS-IS cost

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible \| compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Specify a global IPv6 IS-IS cost.	circuit-cost cost-value [ level-1 \| level-2 ]	By default, no global IPv6 cost is specified.

Enabling automatic link cost calculation

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Enable automatic IPv6 IS-IS cost calculation.	auto-cost enable	By default, automatic IPv6 IS-IS cost calculation is disabled.
7. (Optional.) Configure a bandwidth reference value for automatic IPv6 IS-IS cost calculation.	bandwidth-reference value	The default setting is 100 Mbps.

Tuning and optimizing IPv6 IS-IS networks

Configuration prerequisites

Before you tune and optimize IPv6 IS-IS networks, complete basic IPv6 IS-IS tasks.

Assigning a convergence priority to IPv6 IS-IS routes

A topology change causes IS-IS routing convergence. To improve convergence speed, you can assign convergence priorities to IPv6 IS-IS routes. Convergence priority levels are critical, high, medium, and low. The higher the convergence priority, the faster the convergence speed.

By default, IPv6 IS-IS host routes have medium convergence priority, and other IPv6 IS-IS routes have low convergence priority.

To assign a convergence priority to specific IPv6 IS-IS routes:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible \| compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Assign a convergence priority to specific IPv6 IS-IS routes.	· Method 1: prefix-priority { critical \| high \| medium } { prefix-list prefix-list-name \| tag tag-value } · Method 2: prefix-priority route-policy route-policy-name	By default, IPv6 IS-IS routes, except IPv6 IS-IS host routes, have the low convergence priority.

Setting the LSDB overload bit

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible \| compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Set the overload bit.	set-overload [ on-startup [ [ start-from-nbr system-id [ timeout1 [ nbr-timeout ] ] ] \| timeout2 \| wait-for-bgp4+ [ timeout3 ] ] ] [ allow { external \| interlevel } * ]	By default, the overload bit is not set.

Configuring a tag value on an interface

When IS-IS advertises an IPv6 prefix with a tag value, it adds the tag to the IPv6 reachability information TLV, regardless of the link cost style.

To configure a tag value on an interface:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Configure a tag value on the interface.	isis ipv6 tag tag	By default, no tag value is configured on an interface.

Controlling SPF calculation interval

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible \| compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Set the SPF calculation interval.	timer spf maximum-interval [ minimum-interval [ incremental-interval ] ]	By default: · The maximum interval is 5 seconds. · The minimum interval is 50 milliseconds. · The incremental interval is 200 milliseconds.

Enabling IPv6 IS-IS ISPF

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible \| compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.
6. Enable IPv6 IS-IS ISPF.	ispf enable	By default, IPv6 IS-IS ISPF is enabled.

Enabling prefix suppression

Perform this task to disable an interface from advertising its prefix in LSPs. This enhances network security by preventing IP routing to the interval nodes and speeds up network convergence.

To enable prefix suppression:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Enable prefix suppression on the interface.	isis ipv6 prefix-suppression	By default, prefix suppression is disabled on an interface.

Configuring BFD for IPv6 IS-IS

Bidirectional forwarding detection (BFD) can quickly detect faults between IPv6 IS-IS neighbors to improve the convergence speed of IPv6 IS-IS. For more information about BFD, see High Availability Configuration Guide.

To configure BFD for IPv6 IS-IS:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enable an IS-IS process and enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Configure the NET for the IS-IS process.	network-entity net	By default, no NET is configured.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Return to system view.	quit	N/A
6. Enter interface view.	interface interface-type interface-number	N/A
7. Enable IPv6 for IS-IS on the interface.	isis ipv6 enable [ process-id ]	By default, IPv6 is disabled for IS-IS on an interface.
8. Enable BFD for IPv6 IS-IS.	isis ipv6 bfd enable	By default, BFD for IPv6 IS-IS is disabled.

Configuring IPv6 IS-IS FRR

IMPORTANT:

ECMP routes do not support FRR.

A link or router failure on a path can cause packet loss and routing loop. IPv6 IS-IS FRR enables fast rerouting to minimize the failover time.

Figure 1 Network diagram for IPv6 IS-IS FRR

In Figure 1, after you enable FRR on Router B, IPv6 IS-IS FRR automatically calculates or designates a backup next hop when a link failure is detected. In this way, packets are directed to the backup next hop to reduce traffic recovery time. Meanwhile, IPv6 IS-IS calculates the shortest path based on the new network topology, and forwards packets over the path after network convergence.

You can assign a backup next hop for IPv6 IS-IS FRR in the following ways:

· Enable IPv6 IS-IS FRR to calculate a backup next hop through Loop Free Alternate (LFA) calculation.

· Designate a backup next hop with a routing policy for routes matching specific criteria.

Configuration prerequisites

Before you configure IPv6 IS-IS FRR, complete the following tasks:

· Configure IPv6 addresses for interfaces to ensure IP connectivity between neighboring nodes.

· Enable IPv6 IS-IS.

· Make sure the backup next hop is reachable.

Configuration procedure

Configuring IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. (Optional.) Disable LFA calculation on the interface.	isis ipv6 fast-reroute lfa-backup exclude	By default, the interface participates in LFA calculation and can be elected as a backup interface.
4. Return to system view.	quit	N/A
5. Enter IS-IS IPv6 unicast address family view.	a isis [ process-id ] [ vpn-instance vpn-instance-name ] b address-family ipv6 [ unicast ]	N/A
6. Enable IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation.	fast-reroute lfa	By default, IPv6 IS-IS FRR is disabled.

Configuring IPv6 IS-IS FRR using a routing policy

You can use the apply ipv6 fast-reroute backup-interface command to specify a backup next hop in a routing policy for routes matching specific criteria. You can also perform this task to reference the routing policy for IPv6 IS-IS FRR. For more information about the apply ipv6 fast-reroute backup-interface command and routing policy configurations, see "Configuring routing policies."

To configure IPv6 IS-IS FRR using a routing policy:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. (Optional.) Disable LFA calculation on the interface.	isis ipv6 fast-reroute lfa-backup exclude	By default, the interface participates in LFA calculation, and can be elected as a backup interface.
4. Return to system view.	quit	N/A
5. Enter IS-IS IPv6 unicast address family view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
5. Enter IS-IS IPv6 unicast address family view.	address-family ipv6 [ unicast ]	N/A
6. Enable IPv6 IS-IS FRR using a routing policy.	fast-reroute route-policy route-policy-name	By default, IPv6 IS-IS FRR is disabled.

Enabling BFD for IPv6 IS-IS FRR

By default, IPv6 IS-IS FRR does not use BFD to detect primary link failures. To speed up IPv6 IS-IS convergence, enable BFD for IPv6 IS-IS FRR to detect primary link failures.

To enable BFD control packet mode for IPv6 IS-IS FRR:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter interface view.	interface interface-type interface-number	N/A
3. Enable BFD control packet mode for IPv6 IS-IS FRR.	isis ipv6 primary-path-detect bfd ctrl	By default, BFD control packet mode for IPv6 IS-IS FRR is disabled.

To enable BFD echo packet mode for IPv6 IS-IS FRR:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Configure the source IPv6 address of BFD echo packets.	bfd echo-source-ipv6 ip-address	By default, the source IPv6 address of BFD echo packets is not configured. The source IPv6 address cannot be on the same network segment as any local interface's IP address. For more information, see High Availability Command Reference.
3. Enter interface view.	interface interface-type interface-number	N/A
4. Enable BFD echo packet mode for IPv6 IS-IS FRR.	isis ipv6 primary-path-detect bfd echo	By default, BFD echo packet mode for IPv6 IS-IS FRR is disabled.

Enabling IPv6 IS-IS MTR

On a network, IPv4 and IPv6 topologies must be consistent so that both IPv6 IS-IS and IPv4 IS-IS can use the SPF algorithm to perform route calculation. If they are different, routers supporting both IPv4 and IPv6 might send IPv6 packets to routers that do not support IPv6, resulting in packet loss.

To resolve this issue, configure IPv6 IS-IS Multi-Topology Routing (MTR) to perform route calculation separately in IPv4 and IPv6 topologies.

Figure 2 Network diagram

As shown in Figure 2, the numbers refer to the link costs. Router A, Router B, and Router D support both IPv4 and IPv6. Router C supports only IPv4 and cannot forward IPv6 packets.

Enable IPv6 IS-IS MTR on Router A, Router B, Router C, and Router D to make them perform route calculation separately in IPv4 and IPv6 topologies. With this configuration, Router A does not forward IPv6 packets destined to Router D through Router B, avoiding packet loss.

For more information about MTR and IS-IS MTR, see "Configuring MTR" and "Configuring IS-IS."

Configuration prerequisites

Before you configure IPv6 IS-IS MTR, configure basic IPv4 and IPv6 IS-IS functions, and establish IS-IS neighbors.

Configuration procedure

To enable IPv6 IS-IS MTR:

Step	Command	Remarks
1. Enter system view.	system-view	N/A
2. Enter IS-IS view.	isis [ process-id ] [ vpn-instance vpn-instance-name ]	N/A
3. Specify an IS-IS cost style.	cost-style { wide \| wide-compatible \| compatible }	By default, the IS-IS cost style is narrow.
4. Enter IPv6 address family view.	address-family ipv6 [ unicast ]	N/A
5. Enable IPv6 IS-IS MTR.	multi-topology [ compatible ]	By default, IPv6 IS-IS MTR is disabled.

Displaying and maintaining IPv6 IS-IS

Execute display commands in any view. For other display and reset commands, see "Configuring IS-IS."

Task	Command
Display information about routes redistributed by IPv6 IS-IS.	display isis redistribute ipv6 [ ipv6-address mask-length ] [ level-1 \| level-2 ] [ process-id ]
Display IPv6 IS-IS routing information.	display isis route ipv6 [ ipv6-address ] [ [ level-1 \| level-2 ] \| verbose ] * [ process-id ]
Display IPv6 IS-IS statistics.	display isis statistics ipv6 [ level-1 \| level-1-2 \| level-2 ] [ process-id ]
Display IPv6 IS-IS topology information.	display isis spf-tree ipv6 [ [ level-1 \| level-2 ] \| verbose ] * [ process-id ]

IPv6 IS-IS configuration examples

IPv6 IS-IS basic configuration example

Network requirements

As shown in Figure 3, Router A, Router B, Router C, and Router D, all enabled with IPv6, reside in the same AS. Configure IPv6 IS-IS on the routers so that they can reach each other.

Router A and Router B are Level-1 routers, Router D is a Level-2 router, and Router C is a Level-1-2 router.

Figure 3 Network diagram

Configuration procedure

1. Configure IPv6 addresses for interfaces. (Details not shown.)

2. Configure IPv6 IS-IS:

# Configure Router A.

<RouterA> system-view

[RouterA] isis 1

[RouterA-isis-1] is-level level-1

[RouterA-isis-1] network-entity 10.0000.0000.0001.00

[RouterA-isis-1] address-family ipv6

[RouterA-isis-1-ipv6] quit

[RouterA-isis-1] quit

[RouterA] interface gigabitethernet 1/1/1

[RouterA-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterA-GigabitEthernet1/1/1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] is-level level-1

[RouterB-isis-1] network-entity 10.0000.0000.0002.00

[RouterB-isis-1] address-family ipv6

[RouterB-isis-1-ipv6] quit

[RouterB-isis-1] quit

[RouterB] interface gigabitethernet 1/1/1

[RouterB-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterB-GigabitEthernet1/1/1] quit

# Configure Router C.

<RouterC> system-view

[RouterC] isis 1

[RouterC-isis-1] network-entity 10.0000.0000.0003.00

[RouterC-isis-1] address-family ipv6

[RouterC-isis-1-ipv6] quit

[RouterC-isis-1] quit

[RouterC] interface gigabitethernet 1/1/1

[RouterC-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterC-GigabitEthernet1/1/1] quit

[RouterC] interface gigabitethernet 1/1/2

[RouterC-GigabitEthernet1/1/2] isis ipv6 enable 1

[RouterC-GigabitEthernet1/1/2] quit

[RouterC] interface gigabitethernet 1/1/3

[RouterC-GigabitEthernet1/1/3] isis ipv6 enable 1

[RouterC-GigabitEthernet1/1/3] quit

# Configure Router D.

<RouterD> system-view

[RouterD] isis 1

[RouterD-isis-1] is-level level-2

[RouterD-isis-1] network-entity 20.0000.0000.0004.00

[RouterD-isis-1] address-family ipv6

[RouterD-isis-1-ipv6] quit

[RouterD-isis-1] quit

[RouterD] interface gigabitethernet 1/1/1

[RouterD-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterD-GigabitEthernet1/1/1] quit

[RouterD] interface gigabitethernet 1/1/2

[RouterD-GigabitEthernet1/1/2] isis ipv6 enable 1

[RouterD-GigabitEthernet1/1/2] quit

Verifying the configuration

# Display the IPv6 IS-IS routing table on Router A.

[RouterA] display isis route ipv6

Route information for IS-IS(1)

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

Level-1 IPv6 Forwarding Table

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

Destination : :: PrefixLen: 0

Flag : R/-/- Cost : 10

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Destination : 2001:1:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/1

Destination : 2001:2:: PrefixLen: 64

Flag : R/-/- Cost : 20

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Destination : 2001:3:: PrefixLen: 64

Flag : R/-/- Cost : 20

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

# Display the IPv6 IS-IS routing table on Router B.

[RouterB] display isis route ipv6

Route information for IS-IS(1)

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

Level-1 IPv6 Forwarding Table

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

Destination : :: PrefixLen: 0

Flag : R/-/- Cost : 10

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Destination : 2001:1:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Destination : 2001:2:: PrefixLen: 64

Flag : R/-/- Cost : 20

Next Hop : Direct Interface: GE1/1/1

Destination : 2001:3:: PrefixLen: 64

Flag : R/-/- Cost : 20

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

# Display the IPv6 IS-IS routing table on Router C.

[RouterC] display isis route ipv6

Route information for IS-IS(1)

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

Level-1 IPv6 Forwarding Table

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

Destination : 2001:1:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/2

Destination : 2001:2:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/1

Destination : 2001:3:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/3

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

Level-2 IPv6 Forwarding Table

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

Destination : 2001:1:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/2

Destination : 2001:2:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/1

Destination : 2001:3:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/3

Destination : 2001:4::1 PrefixLen: 64

Flag : R/-/- Cost : 10

Next Hop : FE80::20F:E2FF:FE3E:FA3D Interface: GE1/1/3

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

# Display the IPv6 IS-IS routing table on Router D.

[RouterD] display isis route ipv6

Route information for IS-IS(1)

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

Level-2 IPv6 Forwarding Table

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

Destination : 2001:1:: PrefixLen: 64

Flag : R/-/- Cost : 20

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Destination : 2001:2:: PrefixLen: 64

Flag : R/-/- Cost : 20

Next Hop : FE80::200:FF:FE0F:4 Interface: GE1/1/1

Destination : 2001:3:: PrefixLen: 64

Flag : D/L/- Cost : 10

Next Hop : Direct Interface: GE1/1/1

Destination : 2001:4::1 PrefixLen: 64

Flag : D/L/- Cost : 0

Next Hop : Direct Interface: GE1/1/2

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

BFD for IPv6 IS-IS configuration example

Network requirements

As shown in Figure 4:

· Configure IPv6 IS-IS on Router A, Router B, and Router C so that they can reach each other.

· Enable BFD on GigabitEthernet 1/1/1 of Router A and Router B.

When the link between Router B and the Layer-2 switch fails, BFD can quickly detect the failure and notify IPv6 IS-IS of the failure. Then Router A and Router B communicate through Router C.

Figure 4 Network diagram

Table 1 Interface and IP address assignment

Device	Interface	IPv6 address
Router A	GE1/1/1	2001::1/64
Router A	GE1/1/2	2001:2::1/64
Router B	GE1/1/1	2001::2/64
Router B	GE1/1/2	2001:3::2/64
Router C	GE1/1/1	2001:2::2/64
Router C	GE1/1/2	2001:3::1/64

Configuration procedure

1. Configure IPv6 addresses for interfaces. (Details not shown.)

2. Configure IPv6 IS-IS:

# Configure Router A.

<RouterA> system-view

[RouterA] isis 1

[RouterA-isis-1] is-level level-1

[RouterA-isis-1] network-entity 10.0000.0000.0001.00

[RouterA-isis-1] address-family ipv6

[RouterA-isis-1-ipv6] quit

[RouterA-isis-1] quit

[RouterA] interface gigabitethernet 1/1/1

[RouterA-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterA-GigabitEthernet1/1/1] quit

[RouterA] interface gigabitethernet 1/1/2

[RouterA-GigabitEthernet1/1/2] isis ipv6 enable 1

[RouterA-GigabitEthernet1/1/2] quit

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] is-level level-1

[RouterB-isis-1] network-entity 10.0000.0000.0002.00

[RouterB-isis-1] address-family ipv6

[RouterB-isis-1-ipv6] quit

[RouterB-isis-1] quit

[RouterB] interface gigabitethernet 1/1/1

[RouterB-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterB-GigabitEthernet1/1/1] quit

[RouterB] interface gigabitethernet 1/1/2

[RouterB-GigabitEthernet1/1/2] isis ipv6 enable 1

[RouterB-GigabitEthernet1/1/2] quit

# Configure Router C.

<RouterC> system-view

[RouterC] isis 1

[RouterC-isis-1] network-entity 10.0000.0000.0003.00

[RouterC-isis-1] address-family ipv6

[RouterC-isis-1-ipv6] quit

[RouterC-isis-1] quit

[RouterC] interface gigabitethernet 1/1/1

[RouterC-GigabitEthernet1/1/1] isis ipv6 enable 1

[RouterC-GigabitEthernet1/1/1] quit

[RouterC] interface gigabitethernet 1/1/2

[RouterC-GigabitEthernet1/1/2] isis ipv6 enable 1

[RouterC-GigabitEthernet1/1/2] quit

3. Configure BFD functions:

# Enable BFD and configure BFD parameters on Router A.

[RouterA] bfd session init-mode active

[RouterA] interface gigabitethernet 1/1/1

[RouterA-GigabitEthernet1/1/1] isis ipv6 bfd enable

[RouterA-GigabitEthernet1/1/1] bfd min-transmit-interval 500

[RouterA-GigabitEthernet1/1/1] bfd min-receive-interval 500

[RouterA-GigabitEthernet1/1/1] bfd detect-multiplier 7

[RouterA-GigabitEthernet1/1/1] return

# Enable BFD and configure BFD parameters on Router B.

[RouterB] bfd session init-mode active

[RouterB] interface gigabitethernet 1/1/1

[RouterB-GigabitEthernet1/1/1] isis ipv6 bfd enable

[RouterB-GigabitEthernet1/1/1] bfd min-transmit-interval 500

[RouterB-GigabitEthernet1/1/1] bfd min-receive-interval 500

[RouterB-GigabitEthernet1/1/1] bfd detect-multiplier 6

Verifying the configuration

# Display BFD session information on Router A.

<RouterA> display bfd session

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv6 Session Working Under Ctrl Mode:

Local Discr: 1441 Remote Discr: 1450

Source IP: FE80::20F:FF:FE00:1202 (link-local address of GigabitEthernet1/1/1 on Router A)

Destination IP: FE80::20F:FF:FE00:1200 (link-local address of GigabitEthernet1/1/1 on Router B)

Session State: Up Interface: GE1/1/1

Hold Time: 2319ms

# Display routes destined for 2001:4::0/64 on Router A.

<RouterA> display ipv6 routing-table 2001:4::0 64

Summary Count : 2

Destination: 2001:4::/64 Protocol : IS_L1

NextHop : FE80::20F:FF:FE00:1200 Preference: 15

Interface : GE1/1/1 Cost : 10

The output shows that Router A and Router B communicate through GigabitEthernet 1/1/1. Then the link over GigabitEthernet 1/1/1 fails.

# Display routes destined for 2001:4::0/64 on Router A.

<RouterA> display ipv6 routing-table 2001:4::0 64

Summary Count : 1

Destination: 2001:4::/64 Protocol : IS_L1

NextHop : FE80::BAAF:67FF:FE27:DCD0 Preference: 15

Interface : GE1/1/2 Cost : 20

The output shows that Router A and Router B communicate through GigabitEthernet 1/1/2.

IPv6 IS-IS FRR configuration example

Network requirements

As shown in Figure 5, Router A, Router B, and Router C reside in the same IS-IS routing domain.

· Run IPv6 IS-IS on all the routers to interconnect them with each other.

· Configure IPv6 IS-IS FRR so that when Link A fails, traffic can be switched to Link B immediately.

Figure 5 Network diagram

Table 2 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Router A	GE1/1/1	1::1/64	Router B	GE1/1/1	3::1/64
	GE1/1/2	2::1/64		GE1/1/2	2::2/64
	Loop0	10::1/128		Loop0	20::1/128
Router C	GE1/1/1	1::2/64
	GE1/1/2	3::2/64

Configuration procedure

1. Configure IPv6 addresses for interfaces on the routers and enable IPv6 IS-IS. (Details not shown.)

2. Configure IPv6 IS-IS FRR:

Enable IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation, or designate a backup next hop by using a routing policy.

¡ (Method 1.) Enable IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation:

# Configure Router A.

<RouterA>system-view

[RouterA] isis 1

[RouterA-isis-1] address-family ipv6

[RouterA-isis-1-ipv6] fast-reroute lfa

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] address-family ipv6

[RouterB-isis-1-ipv6] fast-reroute lfa

¡ (Method 2.) Enable IPv6 IS-IS FRR to designate a backup next hop by using a routing policy:

# Configure Router A.

<RouterA> system-view

[RouterA] ipv6 prefix-list abc index 10 permit 20:: 128

[RouterA] route-policy frr permit node 10

[RouterA-route-policy-frr-10] if-match ipv6 address prefix-list abc

[RouterA-route-policy-frr-10] apply ipv6 fast-reroute backup-interface gigabitethernet 1/1/1 backup-nexthop 1::2

[RouterA-route-policy-frr-10] quit

[RouterA] isis 1

[RouterA-isis-1] address-family ipv6

[RouterA-isis-1-ipv6] fast-reroute route-policy frr

[RouterA-isis-1-ipv6] quit

[RouterA-isis-1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] ipv6 prefix-list abc index 10 permit 10:: 128

[RouterB] route-policy frr permit node 10

[RouterB-route-policy-frr-10] if-match ipv6 address prefix-list abc

[RouterB-route-policy-frr-10] apply ipv6 fast-reroute backup-interface gigabitethernet 1/1/1 backup-nexthop 3::2

[RouterB-route-policy-frr-10] quit

[RouterB] isis 1

[RouterB-isis-1] address-family ipv6

[RouterB-isis-1-ipv6] fast-reroute route-policy frr

[RouterB-isis-1-ipv6] quit

[RouterB-isis-1] quit

Verifying the configuration

# Display the route 20::1/128 on Router A to view the backup next hop information.

[RouterA] display ipv6 routing-table 20::1 128 verbose

Summary count : 1

Destination: 20::1/128

Protocol: IS_L1

Process ID: 1

SubProtID: 0x1 Age: 00h27m45s

Cost: 10 Preference: 15

IpPre: N/A QosLocalID: N/A

Tag: 0 State: Active Adv

OrigTblID: 0xa OrigVrf: default-vrf

TableID: 0xa OrigAs: 0

NibID: 0x24000005 LastAs: 0

AttrID: 0xffffffff Neighbor: ::

Flags: 0x10041 OrigNextHop: FE80::34CD:9FF:FE2F:D02

Label: NULL RealNextHop: FE80::34CD:9FF:FE2F:D02

BkLabel: NULL BkNextHop: FE80::7685:45FF:FEAD:102

Tunnel ID: Invalid Interface: GigabitEthernet1/1/2

BkTunnel ID: Invalid BkInterface: GigabitEthernet1/1/1

FtnIndex: 0x0 TrafficIndex: N/A

Connector: N/A

# Display the route 10::1/128 on Router B to view the backup next hop information.

[RouterB] display ipv6 routing-table 10::1 128 verbose

Summary count : 1

Destination: 10::1/128

Protocol: IS_L1

Process ID: 1

SubProtID: 0x1 Age: 00h33m23s

Cost: 10 Preference: 15

IpPre: N/A QosLocalID: N/A

Tag: 0 State: Active Adv

OrigTblID: 0xa OrigVrf: default-vrf

TableID: 0xa OrigAs: 0

NibID: 0x24000006 LastAs: 0

AttrID: 0xffffffff Neighbor: ::

Flags: 0x10041 OrigNextHop: FE80::34CC:E8FF:FE5B:C02

Label: NULL RealNextHop: FE80::34CC:E8FF:FE5B:C02

BkLabel: NULL BkNextHop: FE80::7685:45FF:FEAD:102

Tunnel ID: Invalid Interface: GigabitEthernet1/1/2

BkTunnel ID: Invalid BkInterface: GigabitEthernet1/1/1

FtnIndex: 0x0 TrafficIndex: N/A

Connector: N/A

07-Layer 3 - IP Routing Configuration Guide

Overview

Configuring basic IPv6 IS-IS

Configuring IPv6 IS-IS route control

Configuring an IPv6 IS-IS cost for an interface

Configuring a global IPv6 IS-IS cost

Enabling automatic link cost calculation

Tuning and optimizing IPv6 IS-IS networks

Controlling SPF calculation interval

Configuring BFD for IPv6 IS-IS

Configuring IPv6 IS-IS FRR

Configuring IPv6 IS-IS FRR to calculate a backup next hop through LFA calculation

Configuring IPv6 IS-IS FRR using a routing policy

Enabling BFD for IPv6 IS-IS FRR

Configuration prerequisites

Configuration procedure

Displaying and maintaining IPv6 IS-IS

Network requirements

Configuration procedure

Verifying the configuration

BFD for IPv6 IS-IS configuration example

Network requirements

Configuration procedure

Verifying the configuration

IPv6 IS-IS FRR configuration example

Network requirements

Configuration procedure

Verifying the configuration

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