Deploy IS-IS as the Service Provider Underlay IGP¶

Note

The LDP and IP-VPN Labs of the Routing ATD are structured to build on each other. You should complete all labs before moving onto the next. Alternatively, using the Lab Selection Menus will complete configurations for prior labs as necessary.

Preparing The Lab¶

Log into the LabAccess jumpserver:
1. Type labs, or select Option 97 to get to the Additional Labs menu.
2. Type or select the option for mesh-topology-ipvpn-labs to access the LDP and IPVPN labs.
3. Type reset in this menu to configure the topology with the necessary prerequisites.
Did You Know?

The reset option (and all other options) makes use of CloudVision Portal APIs to apply configlets to each EOS node ensuring they have the proper configuration.

Verification¶

Before starting any configuration, we want to check and verify the topology's base status on EOS1.

Verify interface configurations and neighbors.

Command Syntax

Full commands will be typed for reference in lab steps, but commands in EOS can be shortened or tab-completed at the user’s discretion.
```
show ip interface brief
show ipv6 interface brief
show run interfaces Ethernet1-5
show lldp neighbors
```

Verify there is no routing protocol configuration or neighbors present as of yet:

show run section isis
show run section bgp
show isis neighbors
show ip bgp summary

Lab Tasks¶

Configure the IS-IS routing protocol on EOS1 using the following steps:
1. Enable IS-IS with an instance ID of 100 and define a NET (1). For the NET, use the format of 49.1111.0000.000 (EOS ID) .00 where 1111 is the IS-IS area ID and 0000.000 (EOS ID) is the System ID.
  1. Network Entity Title
  Note
  
  Arista EOS utilizes the Industry-Standard CLI. When entering configuration commands, be sure to first type configure to enter configuration mode.
```
router isis 100
    net 49.1111.0000.0001.00
```
2. Set the IS-IS level to level-2 and activate the IPv4 and IPv6 unicast address-family to ensure the router will hold all backbone IPv4 and IPv6 routes.
  
  Note
  
  Our topology will maintain only IS-IS level-2 adjacenies. This will give us a single backbone area where all routes will be learned by all routers (similar to an OSPF topology where all routers are in area 0). This is sufficient for smaller topologies where there isn’t a need to segment flooding domains.
```
router isis 100
    is-type level-2
    !
    address-family ipv4 unicast
    !
    address-family ipv6 unicast
```
3. To shrink the overall size of the LSDB and routing table, we will only advertise Loopback /32 networks to other EOS routers and not individual link addressing. This is accomplished by only advertising passive IS-IS interfaces and networks.
```
router isis 100
    advertise passive-only
```
4. Enable BFD in the IPv4 and IPv6 address-families for detection of faults in neighbor communication.
```
router isis 100
    !
    address-family ipv4 unicast
        bfd all-interfaces
    !
    address-family ipv6 unicast
        bfd all-interfaces
```
5. Enable IPv6 Multi-Topology for IS-IS to ensure each address-family has the ability to maintain a discrete view of the network.
```
router isis 100
    !
    address-family ipv6 unicast
        multi-topology
```
6. Adjust SPF and LSP timers for customization of protocol behavior within IS-IS.
  
  Info
  
  The timer values here are just examples. Since the lab environment is virtualized in the cloud, performance can be unpredictable if the timer values are set too aggressively in the virtual lab.
```
router isis 100
    spf-interval 5 1000 2000
    timers lsp generation 5 1000 2000
```
7. Enable Dynamic Flooding for IS-IS so a discrete restricted flooded topology is calculated for LSP flooding to reduce load on each router’s control-plane.
  
  Info
  
  Dynamic flooding is most beneficial in highly redundant topologies with many adjacencies.
```
router isis 100
    lsp flooding dynamic level-2
```
8. Finally, ensure IS-IS explicitly logs all neighbor state changes.
```
router isis 100
    log-adjacency-changes
```
9. Verify protocol configuration thus far.
  
  ???+ tip "Pro Tip" You do not need to exit configuration mode to execute show commands in EOS.
```
show run section isis
```
Configure IS-IS interfaces on EOS1:
1. All links connecting to other SP routers (EOS1 through EOS8) will form IS-IS adjacenies. Configure the link between EOS1 and EOS2 as an IS-IS interface.
```
interface Ethernet1
    isis enable 100
```
2. Additionally, since this is point to point link to a level-2 router, we will define those characteristics to ensure proper peering and bypass unnecessary DIS elections.
```
interface Ethernet1
    isis circuit-type level-2
    isis network point-to-point
```
3. Repeat the above configurations for the other interfaces on EOS1 that are attached to adjacent SP nodes. Refer to the diagram above and LLDP neighbor information for interfaces requiring configuration.
  
  Pro Tip
  
  You can configure multiple interfaces at once using ranges and separators in EOS. For example, EOS1 interfaces Et2, 4 and 5 require IS-IS configuration, but the commands are the same for all interfaces. You can type interface Ethernet2,4-5 to enter configurations for all three at once.
4. Next, the Loopback0 interface needs to be activated as an IS-IS interface.
```
interface Loopback0
    isis enable 100
```
5. Lastly, since Loopback0 is not attached to another router, we can set it as a passive interface for IS-IS to ensure proper operation.
```
interface Loopback0
    isis passive
```
  Note
  
  In addition, this command works in conjunction with the advertise passive-only command in our IS-IS protocol configuration. It ensures only our passive (i.e. Loopback0) interfaces will be advertised.
Since no other devices have been configured, there are no peers as of yet. Configure EOS2 using the same steps above.

Note

Each EOS node requires a unique NET. Following the format described above, EOS2 will have a NET of 49.1111.0000.0002.00 under the IS-IS configuration. In addition, interfaces Et1 through 5 are all attached to SP routers so will require IS-IS configuration.

Testing¶

With both EOS1 and EOS2 configured, verify IS-IS peering and route advertisement:

Verify IS-IS adjacency and LSDB.
```
show isis neighbors
show isis interface
show isis database detail
show isis dynamic flooding topology
```
Note

IS-IS will automatically convert system IDs to configured hostnames to make show outputs easier to interpret.
Verify routing table only show IS-IS routes for the associated Loopback0 /32 networks.
```
show ip route
```

Test reachability between Loopback0 interfaces from EOS1 to EOS2.

ping 2.2.2.2 source 1.1.1.1
ping ipv6 2:2:2::2 source 1:1:1::1

Final Lab Tasks¶

Configure the remaining Service Provider nodes (EOS3 - EOS8) for IS-IS using the steps above. Verify routing tables only show advertised Loopback0 interfaces for all nodes.

Success

Lab Complete!