IS-IS notes

General:
- routing protocol for ISO CLNP (Connectionless Network Protocol)
- NET (Network Entity Title) required by configuration (L3 address) Has different formats. One practical is below:
   Area (1-13 bytes)| System ID (6 bytes) | Selector (1 byte) (eg. 47.000|1921.6810.0001|00)
   Selector is 00 in a NET. The NET must begin with one octet (eg 47) and end with one octed (00)
   Selector is non 00, the address is NSAP (Network Service Access Point)
   NSAP describes a service attachment at the network layer (similar to IP protocol at the IP layer)
- operates over Ethernet 802.2 LLC  (not over the common Ethernet II)
- dual ISIS (RFC1195) supports CLNS and IP
- hierarchical with 2 level hierarchy (L2 - core)
- ignores TLVs it does not understand


Adjacencies:
- L1 area ID must be the same