ISIS IPv6 Configuration Workbook 3

In this blog post, we’ll walk through a practical lab scenario focused on ISIS IPv6 configuration and addressing in a multi-area network environment. This guide is based on Workbook 3 and builds upon previous IS-IS knowledge.

We’ll cover setting up IS-IS adjacencies in new areas (0004, 0005, and 0006), understanding different NET (Network Entity Title) formats, and configuring IPv6 addresses on routers.

This workbook follows on from Workbook 2 ISIS IPv4 Troubleshooting with Route Policies, Authentication and follows RFC5308

ISIS Topology Overview:

• Routers: IOS XR – PE1, PE4, PE13 and PE22
• Routers: IOS XE – CE1, CE2, CE4, PE10, CE11, PE12 and PE23
• Routing Protocol: IS-IS IPv4 and IPv6
• Existing Design:
  • Areas 0001, 0002, and 0003 are already configured with IPv6 and IS-IS for both IPv4 and IPv6.
• New Areas:
  • Area 0004
  • Area 0005
  • Area 0006

Task 1: Configuring ISIS IPv4 Adjacencies

This task involves setting up IS-IS adjacencies in the three new areas with specific NET address formats:

• Area 0004: 49.area.xxxx.router.nsel (e.g., 49.0004.0000.0010.00)
• Area 0005: 49.area.xxxx.xxxx.router.nsel (e.g., 49.0005.0000.0000.0012.00)
• Area 0006: 49.area.xxxx.xxxx.router.nsel (e.g., 49.0006.0000.0000.0013.00)

Key Considerations:

• NET Address Format: The key difference is the System ID portion. Area 0004 uses a 6-byte System ID (xxxx.router), while Areas 0005 and 0006 use an 8-byte System ID (xxxx.xxxx.router).
• IS-IS Process Naming: The IS-IS process is named after the area (e.g., area4, area5, area6).

ISIS Configuration Solutions

PE10#show run | s isis
router isis area4
 net 49.0004.0000.0010.00
 passive-interface Loopback0

PE10#
interface Loopback0
 ip address 100.10.10.10 255.255.255.255
 ipv6 address 2222:DB8:100::10/128
!
interface GigabitEthernet1
 ip address 10.2.11.10 255.255.255.0
 ip router isis area4
 ipv6 address 2002:DB8:1011::10/64
!
interface GigabitEthernet3
 ip address 23.2.10.10 255.255.255.0
 ip router isis area4
 ipv6 address 2002:DB8:2310::10/64

router isis area4
 net 49.0004.0000.0011.00
 passive-interface Loopback0
 
 interface Loopback0
 ip address 100.11.11.11 255.255.255.255
 ipv6 address 2222:BD8:100::11/128
!
interface GigabitEthernet1
 ip address 10.2.11.11 255.255.255.0
 ip router isis area4
 ipv6 address 2002:DB8:1011::11/64

router isis area5
 net 49.0005.0000.0000.0012.00
 passive-interface Loopback0
!
interface Loopback0
 ip address 100.12.12.12 255.255.255.255
 ipv6 address 2222:DB8:100::12/128
!
interface GigabitEthernet2
 ip address 1.2.12.12 255.255.255.0
 ip router isis area5
 ipv6 address 2002:DB8:1212::12/64
 ipv6 router isis area5
 isis circuit-type level-2-only
!
interface GigabitEthernet3
 ip address 22.2.12.12 255.255.255.0
 ip router isis area5
 ipv6 address 2002:DB8:2212::12/64
 isis circuit-type level-2-only

interface Loopback0
 ipv4 address 100.13.13.13 255.255.255.255
 ipv6 address 2222:db8:100::13/128
!
interface GigabitEthernet0/0/0/2
 ipv4 address 22.2.13.13 255.255.255.0
 ipv6 address 2002:db8:2213::13/64
!
interface GigabitEthernet0/0/0/3
 ipv4 address 1.2.13.13 255.255.255.0
 ipv6 address 2002:db8:1213::13/64
!
router isis area6
 net 49.0006.0000.0000.0013.00
 address-family ipv4 unicast
 !
 interface Loopback0
  passive
  address-family ipv4 unicast
 !
 interface GigabitEthernet0/0/0/2
  circuit-type level-2-only
  address-family ipv4 unicast
 !
 interface GigabitEthernet0/0/0/3
  circuit-type level-2-only
  address-family ipv4 unicast

Verification:

• show isis neighbors (IOS XR)
• show clns neighbors (IOS XE)
• show isis database (IOS XR and IOS XE)

Task 2: Configuring IPv6 Addressing

The next step is to configure IPv6 addresses on the routers within the new areas. This includes:

• Global Unicast Addresses: Addresses routable on the global internet (e.g., 2001:DB8:4::/64).
• Link-Local Addresses: Addresses for local communication within a link (e.g., FE80::/10).

Configuration CE11

interface GigabitEthernet1
 ipv6 address 2001:DB8:4::11/64
 ipv6 enable
 ipv6 router isis area4

Verification:

• show ipv6 interface brief (IOS XE)
• show ipv6 interface (IOS XR)
• show ipv6 route (IOS XR and IOS XE)

Questions and Answers:

Here are the questions posed in the workbook and their answers:

• What is the difference between using the different ID format in the NET address?
  • The difference is the length of the System ID. A 6-byte System ID (e.g., xxxx.router) allows for fewer unique router IDs within an area compared to an 8-byte System ID (e.g., xxxx.xxxx.router). The 8-byte format provides greater scalability for larger networks.
• What is the correct length in bytes for the ID value?
  • The ID value (System ID) is either 6 bytes or 8 bytes, excluding the area ID and NSEL.
• How do you perform a ping to an IPv6 global address?
  • Use the ping command followed by the global IPv6 address: ping 2001:DB8:4::11
• What do you have to include when attempting to ping a link-local address?
  • You must specify the outgoing interface using the % symbol: ping FE80::a%GigabitEthernet0/0

Examining the ISIS Database:

The show isis database (and show ipv6 isis database) commands are crucial for verifying:

• IS-IS Adjacencies: Confirming that routers have formed neighbor relationships.
• IPv6 Reachability: Seeing the IPv6 prefixes learned through IS-IS.
• LSP Information: Examining the Link-State Packets to understand network topology.

ISIS IPv6 Configuration Key Takeaways:

• IS-IS supports different NET address formats to accommodate varying network sizes.
• IPv6 addressing is integrated with IS-IS to enable IPv6 routing.
• Pinging link-local IPv6 addresses requires specifying the outgoing interface.
• The IS-IS database provides valuable information for verification and troubleshooting.