Basics Of IS-IS

IS-IS(ISO 10589) is Integrated System to Integrated System which was initially designed by DEC for OSI then tuned to work for TCP/IP protocol by the IETF in RFC 1195. In other words we can say a robust protocol which now supports the both ip as well as CLNP applications. It is a link state routing protocol and uses the same DIJKSTRA algorithm as being used by OSPF (Open Shortest Path First) to calculate the path cost.
IS-IS maintains three types of tables:-
1. Neighbor Table
2. Routing Table
3. Topology Table

Address Format Used By IS-IS
OSI uses connectionless Network Service aka CLNS which is equivalent to IP in TCP/IP. CLNP assigning addresses to a router called Network Service Access Point(NSAP) addresses or Network Entity Title(NET) addresses. IS-IS uses a one address per node. Net addresses can be up to 20 bytes in length. CISCO implementation of NET address tells about area, system id and NSAP selector.

Types Of Router
1. Level 1 (L1) – It maintains the topology database of its own area.
2. Level 2 router consider as backbone router.
3. Level 1-2 routers are interfaces between the Level 1 and Level 2.

The main advantage of using IS-IS because of it’s TLV (Type/Length/Value) which makes it unique from legacy OSPF. It is a hearsay that support of IPv6 in OSPF requires lot of modification from it’s root but the presence of TLV in IS-IS helped it to support IPv6 with no more changes.


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Which Protocol Is Used As IGP For IPv6?

Selection of IGP for IPv6 is agnostic for dual stack scenarios in mpls vpn backbones or ip backbones. Everyone is having a question that we are using OSPF as IGP for IPv4, which protocol is used as IGP for IPv6. No one is actually putting light which one is best for IPv6 where in OSPF already deployed for IPv4 in most of the cases. During reading RFC 4029 “Selection and Analysis For Introducing IPv6 into SP Networks”, I found section 4.3.1 of IGP which is explicitly defining the protocols require for IGP in IPv6 deployments. According to RFC OSPFv3,IS-IS is used but CISCO is also providing IPv6 support for EIGRP and RIPng is clearly renounce. If we are using the same protocol for both IPv6 as well as for IPv6, it may lead to lot of the problems in case of instability of links because every time protocol has to calculate the path for each and every link. But in case of different protocols for IPv4 and IPv6, the problem in one protocol may not affect another but this requires lot of CPU as well as memory.

Possible combinations are as follows:
1. OSPFv2 for IPv4, IS-IS for IPv6 (only)
2. OSPFv2 for IPv4, OSPFv3 for IPv6
3. IS-IS for IPv4, OSPFv3 for IPv6
4. S-IS for both IPv4 and IPv6
When IS-IS is used for both IPv4 as well as for IPv6, the IPv6/IPv6 topologies must be convex, unless multiple-topology IS-IS extensions have been implemented.


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CCNA, CCNP, CCIE - Service Provider Operation Track

Cisco Announces New Service Provider Operations Track

Built on the growing demand for dedicated professionals who can manage, maintain and troubleshoot complex service provider IP NGN core network infrastructures, Cisco is introducing a new Service Provider (SP) Operations track. This new track is focused on developing associate, professional and expert-level capabilities to operate large, complex SP networks. These new, first of their kind certifications are designed specifically for Cisco Service Provider Customers, Partners and Cisco Networking Engineers.

Over the coming months Cisco will release new CCIE, CCNP, and CCNA SP Operations courses and exams. In addition, the written exam topics for the CCIE SP Operations certification are now available on the Cisco Learning Network. The CCIE SP Operations written exam is scheduled for release in the second quarter of 2010.
For more click here

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