2022-06-27 advanced network engineering (XII) IS-IS overhead type, overhead calculation, LSP processing mechanism, route revocation, route penetration

Cost type

[R1-isis-1]cost-style ?
  compatible         Set cost style to compatible
  narrow             Set cost style to narrow
  narrow-compatible  Set cost style to narrow-compatible
  wide               Set cost style to wide
  wide-compatible    Set cost style to wide-compatible

Width measurement -wide

expenses = Reference bandwidth / Interface bandwidth *10, Reference bandwidth range 1-16777214, The default value of reference bandwidth is 1000.

Narrow metric -narrow

The default type , Overhead range 1-63, The default value 10.

Width measurement （ Compatibility mode ）-wide-compatible

Compatible with width measure and narrow measure LSP, This machine only sends messages with width （ Include width in the message TLV）

Narrow metric （ Compatibility mode ）-narrow-compatible

Compatible with width measure and narrow measure LSP, This machine only sends narrow metric messages （ Include narrow metrics in the message TLV）

Compatibility mode -compatible

Compatible with width measure and narrow measure LSP, This machine only sends messages with two measurements （ There are two measures in the message TLV）

Different overhead types can establish adjacency relationships , But because TLV Different types , stay 3 Under two combinations , There is an interface that cannot receive the other party's route .

1 wide（ No other route ） and narrow（ No other route ）

2 wide-compatible（ There is another route ） and narrow（ No other route ）

3 narrow-compatible（ There is another route ） and wide（ No other route ）

Cost calculation

1 Internal cost calculation ： Add 10. stay level-1 Area , Go to level-2 The route of the area is the default route , The cost is fixed as 10.

2 External cost calculation ：wide The type remains the same .narrow Type overhead =64+ External routing overhead +10* Number of incoming links .

Relevant command

Introduce external routing

[R1-isis-1]import-route direct level-1 cost 20

PS： By default , The route introduced is level-2 Of .

LSP Processing mechanism

‘

If you receive LSP Better than local LSP It's better , Or not received locally LSP

In the broadcast network ： Add it to the database , And send new messages via multicast LSP.

In a point-to-point network ： Add it to the database , And send the PSNP To acknowledge receipt of this message LSP, Then put this new LSP Send to in addition to sending the LSP Neighbors other than your neighbors .

If you receive LSP And local LSP Can't compare the good and the bad , The... Is not processed LSP.

Route revocation

Internal routing ： Announce link status serial number +1 Of LSP

External routing ： The expiration time of the notice is 0 Of LSP

Route penetration

because level-1 Area visit level-2 The area is through level-1-2 The default route issued . On demand level-1 The router in the area should level-2 When routing a specific area , The default route is unreliable 了 , for example , When level-1 There are multiple stations in the area level-1-2 Router , When there is a suboptimal path , In this scenario, you can use Send the default route level-1-2 Configuration on router introduce level-2 Route the area to level-1 Regional implementation requirements .

Relevant command

introduce level-2 All routes in the area are routed to level-1 Area

[R2-isis-1]import-route isis level-2 into level-1 

By configuring ACL And adding route filter parameters to introduce the specified route

[R2-isis-1]import-route isis level-2 into level-1 filter-policy 2000