Is-Is Pdu Format; Is-Is Configuration Task List - H3C S7500 Series Operation Manual

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Operation Manual – Routing Protocol

H3C S7500 Series Ethernet Switches

For example, there is a NET named 47.0001.aaaa.bbbb.cccc.00, where:

Area=47.0001, System ID=aaaa.bbbb.cccc, SEL=00.

Here is another example. A NET named 01.1111.2222.4444.00 exists where:

Area=01, System ID=1111.2222.4444, SEL=00.

5.1.4 IS-IS PDU Format

Directly encapsulated in data link layer frames, IS-IS packets fall into three categories:

Hello, LSP, and SNP.

The Hello packet is used by routers to establish and maintain the neighbor

relationship. It is also called IS-to-IS Hello PDUs (IIH). For broadcast network, the

Level-1 router uses the Level-1 LAN IIH; and the Level-2 router uses the Level-2 LAN

IIH. The P2P IIH is used on point-to-point network. Point-to-Point IIH is used on a

non-broadcast network.

II. LSP packet format

The link state PDUs (LSP) carry link state information. There are two types: Level-1

LSP and Level-2 LSP. The Level-2 LSP is sent by the Level-2 router, and the Level-1

LSP is sent by the Level-1 router. The level-1-2 router can sent both types of the

III. SNP format

The sequence number PDUs (SNP) confirms the latest LSPs received by neighbors.

It is similar to the Acknowledge packet, but more efficient.

The SNP contains the complete SNP (CSNP) and the partial SNP (PSNP), which are

further divided into Level-1 CSNP, Level-2 CSNP, Level-1 PSNP and Level-2 PSNP.

PSNP only contains the sequence numbers of one or multiple latest received LSPs. It

can acknowledge multiple LSPs at one time. When LSDBs are not synchronized, a

PSNP is used to request new LSPs from neighbors.

CSNP covers the summary of all LSPs in the LSDB to synchronize the LSDB between

neighboring routers. On broadcast networks, CSNP is sent by the DIS periodically

(10s by default). On point-to-point networks, CSNP is only sent during the first

adjacency establishment.

Complete the following tasks to configure IS-IS:

Chapter 5 IS-IS Configuration

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