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This chapter describes how to configure advanced FabricPath features, such as using the Intermediate System-to-Intermediate System (IS-IS) protocol on Cisco NX-OS 5500 Series switches.
This chapter includes the following sections:
Note For information about prerequisites, guidelines and limitations, and licensing requirements for FabricPath, see Chapter1, “Overview”
Layer 2 IS-IS is based on Layer 3 IS-IS with enhancements to run on Layer 2. The commands for Layer 2 IS-IS and Layer 3 IS-IS are not the same. Layer 2 IS-IS is the control plane in FabricPath and a single protocol controls all unicast and multicast traffic. From a forwarding perspective, FabricPath Layer 2 IS-IS forwards traffic for unicast, unknown unicast, broadcast, and multicast frames. Using Layer 2 IS-IS, the software maintains loop-free paths throughout the FabricPath network. For information on default FabricPath Layer 2 IS-IS functionality, see “Configuring FabricPath Switching,”. For information on FabricPath forwarding, see “Configuring FabricPath Forwarding,”.
You can use these advanced FabricPath Layer 2 IS-IS configurations to fine-tune the operation of the FabricPath network.
We recommend that you run the FabricPath network using the default Layer 2 IS-IS configurations.
You can change many of the IS-IS settings as follows:
If you change any of the FabricPath Layer 2 IS-IS settings, ensure that you make the same changes for those global parameters on every switch in the FabricPath network and for those parameters on every applicable FabricPath switch in the network.
IS-IS uses the overload bit to tell other routers to not use the local router to forward traffic but to continue routing traffic destined for that local router.
You can use the overload bit in these situations:
The overload bit feature is not backward compatible. For this feature to work properly, all FabricPath switches must support this feature.
You can configure the router to signal other routers not to use this router as an intermediate hop in their shortest path first (SPF) calculations. You can optionally configure the overload bit temporarily on startup until BGP converges.
In addition to setting the overload bit, you might also want to suppress certain types of IP prefix advertisements from LSPs for Level 1 or Level 2 traffic.
Although the Layer 2 IS-IS protocol functions automatically after you enable FabricPath you can optionally configure parameters. You globally configure some FabricPath Layer 2 IS-IS parameters and some parameters you configure per switch. This section includes the following topics:
Note Graceful restart of IS-IS is not supported in Cisco 5500 Series Switches. While the graceful-restart command exists in the CLI, it is not supported at this time.
3. (Optional) authentication-check
4. (Optional) authentication key-chain auth-key-chain-name
5. (Optional) authentication type { cleartext | md5 }
6. (Optional) log-adjacency-changes
7. (Optional) lsp-gen-interval msecs [ msecs msecs ]
9. (Optional) max-lsp-lifetime secs
10. (Optional) maximum-paths max-paths
11. (Optional) reference-bandwidth { ref-mbps [ Mbps ] | ref-gbps [ Gbps ]}
12. (Optional) spf-interval msecs [ msecs msecs ]
13. (Optional) topology topology number
14. (Optional) hostname dynamic
15. (Optional) root-priority value
16. (Optional) set-overload-bit {always | on-start-up { seconds }}
For more information on IS-IS commands, see the Cisco Nexus 5500 Series NX-OS Unicast Routing Configuration Guide, Release 7.x.
Although the FabricPath Layer 2 IS-IS protocol works automatically once you enable FabricPath, you can optionally configure the interface parameters.
2. interface { ethernet mod/slot | port-channel channel-number }
3. (Optional) fabricpath isis authentication-check
4. (Optional) fabricpath isis authentication key-chain auth-key-chain-name
5. (Optional) fabricpath isis authentication type { cleartext | md5 }
6. (Optional) fabricpath isis csnp-interval seconds
7. (Optional) fabricpath isis hello-interval seconds
8. (Optional) fabricpath isis hello-multiplier multiplier
9. (Optional) fabricpath isis hello-padding
10. (Optional) fabricpath isis lsp-interval milliseconds
11. (Optional) fabricpath isis metric metric
12. (Optional) fabricpath isis retransmit-interval seconds
13. (Optional) fabricpath isis retransmit-throttle- interval milliseconds
See the Cisco Nexus 5500 Series NX-OS Unicast Routing Configuration Guide, Release 7.x and the Cisco Nexus 5500 Series NX-OS FabricPath Command Reference for more information on IS-IS commands.
Step 1 (Optional) clear fabricpath isis adjacency [ * | system-id | interface { ethernet mod/slot | port-channel channel-number }]
Step 2 (Optional) clear fabricpath isis statistics *
Step 3 (Optional) clear fabricpath isis traffic [ * | interface { ethernet mod/slot | port-channel channel-number }]
The Multi-Destination Tree (MDT) feature removes the restriction of two MDTs per topology and permits a user to configure up to 16 MDTs per topology. This feature allows load-sharing of multicast traffic across different multi-destination trees within a topology, which improves the network performance.
An MDT, also referred to as a Forwarding Tag or FTag, is a spanning tree used for forwarding packets within a topology. By default, a topology has two MDTs FTags: topology 0 has 1 and 2, topology 1 has FTag 3 and 4. In a default configuration, the first ftag of a topology is used for broadcast and unknown unicast. The second is used for multicast only. In addition, multicast traffic might use the first FTag for load sharing.
Note The 256 and 257 FTags are reserved ftags used for a CE VPC topology.
Configuration and usage of MDT on the Cisco Nexus device needs to follow the following rules:
For example, if there are ten switches in a fabricpath network and nine switches are configured with 8 MDTs but the tenth switch is not configured with MDT, then by this rule, the tenth switch advertises its maximum supported trees as two. Each switch has two MDTs, which is the minimum number of MDTs in the fabricpath network.
For example, if there are three switches in the FabricPath network and each of these switches is configured with 8 MDTs, each switch would have (8 - 3 = 5) zero rooted trees. Only three trees are used with each node acting as the root for each tree.
For example, if there are four nodes and four MDTs configured and later the administrator configures eight MDTs on all four nodes, we see four MDTs and the root calculation remains the same.
For example, if there are three switches in the FabricPath network and switch 1 = 3 MDTs, switch 2 = 5 MDTs, switch 3 = 8 MDTs, the total number of MDTs seen on the setup is three.
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switch(config-fabricpath-isis)# multi-destination trees tree-num |
Specifies the number of multi-destination trees for a topology. |
You can configure MDT per topology.
To display FabricPath information for advanced configurations perform one of the following tasks: