Reference Guide

Intermediate System to Intermediate System | 493
Implementation Information
IS-IS implementation supports one instance of IS-IS and six areas. The system can be configured as a
Level 1 router, a Level 2 router, or a Level 1-2 router. For IPv6, the IPv4 implementation has been
expanded to include two new type-length-values (TLV) in the protocol data unit (PDU) that carry
information required for IPv6 routing. The new TLVs are IPv6 Reachability and IPv6 Interface Address.
Also, a new IPv6 protocol identifier has also been included in the supported TLVs. The new TLVs use the
extended metrics and up/down bit semantics.
Multi-Topology IS-IS adds TLVs:
• The Multi-Topology TLV contains one or more Multi-Topology IDs in which the router participates.
This TLV is included in IIH and the first fragment of an LSP.
• The MT Intermediate Systems TLV appears for every topology a node supports. An MT ID is added to
the extended IS reachability TLV type 22.
• The Multi-Topology Reachable IPv4 Prefixes TLV appears for each IPv4 announced by an IS for a
given MT ID. Its structure is aligned with the extended IS Reachability TLV Type 236 and it adds an
MT ID.
• The Multi-Topology Reachable IPv6 Prefixes TLV appears for each IPv6 announced by an IS for a
given MT ID. Its structure is aligned with the extended IS Reachability TLV Type 236 and add a MT
ID.
By default, Dell Networking OS supports dynamic hostname exchange to assist with troubleshooting and
configuration. By assigning a name to an IS-IS NET address, you can track IS-IS information on that
address easier. Dell does not support ISO CLNS routing; however, the ISO NET format is supported for
addressing.
To support IPv6, the Dell Networking implementation of IS-IS performs the following tasks:
• Advertise IPv6 information in the PDUs
• Process IPv6 information received in the PDUs
• Compute routes to IPv6 destinations
• Download IPv6 routes to RTM for installing in the FIB
• Accept external IPv6 information and advertise this information in the PDUs
Table 26-1 displays the default values for IS-IS.
Table 26-1. IS-IS Default Values
IS-IS Parameter Default Value
Complete Sequence Number PDU (CSNP) interval 10 seconds
IS-to-IS hello PDU interval 10 seconds
IS-IS interface metric 10
Metric style Narrow
Designated Router priority 64
Circuit Type Level 1 and Level 2