Juniper IGP - CONFIGURATION GUIDE V11.1.X, Руководство по настройке

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hierarchical routing design is used. With this model, routing is referred to as level 1,
level 2, or both level 1 and level 2.
IS-IS Terms
OSI internetworking has its own terminology. A number of terms used in IS-IS routing
discussions are defined in Table 13 on page 326.
Table 13: IS-IS Terms
Meaning Term
A group of contiguous networks and their attached hosts. Area
boundaries are normally assigned by a network administrator. area
PDU sent by designated router to ensure database synchronization complete sequence number
PDU (CSNP)
An OSI network layer protocol used by CLNS to handle data at the
transport layer; the OSI equivalent of IP Connectionless Network
Protocol (CLNP)
An OSI network layer service that enables data transmission
without establishing a circuit and that routes messages
independently of any other messages. Connectionless Network
Service Protocol (CLNS)
Any nonrouting network node or host end system (ES)
A router intermediate system (IS)
■
Routing within an area
■
Level 1 routers (or intermediate systems) track all the
individual links, routers, and end systems within a level 1
area.
■
Level 1 routers do not know the identity of routers or
destinations outside their area.
■
A level 1 router forwards all traffic for destinations outside
its area to the nearest level 2 router within its area.
level 1 routing
■
Routing between areas
■
Level 2 routers know the level 2 topology and know which
addresses are reachable via each level 2 router.
■
Level 2 routers track the location of each level 1 area.
■
Level 2 routers are not concerned with the topology within
any level 1 area (for example, the details internal to each level
1 area).
■
Level 2 routers can identify when a level 2 router is also a
level 1 router within the same area.
■
Only a level 2 router can exchange packets with external
routers located outside its routing domain.
level 2 routing
PDU broadcast by link-state protocols that contains information
about neighbors and path costs; used to maintain routing tables;
also known as link-state advertisement link-state PDU (LSP)
326 ■
Overview
JUNOSe 11.0.x IP, IPv6, and IGP Configuration Guide