DISCUSIÓN - UNIVERSIDAD DE LA REPÚBLICA FACULTAD DE VETERINARIA

Normal Areas

66 66 ASBR ASBR A ABBRR--11 AABBRR--22 Internal Internal Area 51 Area 51 Area 1 Area 1 Area 0 Area 0 172.16.0.0/16 172.16.0.0/16 172.16.1.0/24 172.16.1.0/24 172.16.51.0/24 172.16.51.0/24 172.16.10.4/30 172.16.10.4/30 172.16.20.0/24 172.16.20.0/24 10.1.0.0/24 10.1.0.0/24 11.0.0.0/8 11.0.0.0/8 12.0.0.0/8 12.0.0.0/8 13.0.0.0/8 13.0.0.0/8 .1 .1 .1 .1 ..22 ..33 .5 .5 .6 .6 .1 .1 Lo - RouterID Lo - RouterID 192.168.2.1/32 192.168.2.1/32 Lo - RouterID Lo - RouterID 192.168.1.1/32 192.168.1.1/32 Lo - RouterID Lo - RouterID 192.168.3.1/32 192.168.3.1/32 Pri 100 Pri 100 Pri 200 Pri 200 Lo - RouterID Lo - RouterID 192.168.4.1/32 192.168.4.1/32

Normal Areas

LSA 5 LSA 5 LSA 5 LSA 5 LSA 5 LSA 5 LSA 5 LSA 5 LSA 5’s flooded LSA 5’s flooded LSA 5 LSA 5 ASBR ASBR rou

router ter ospospff 11

redistribute static redistribute static

network 172.16.1.0 0.0.0.255 area 0 network 172.16.1.0 0.0.0.255 area 0 ip

ip routroute 11.0.0.e 11.0.0.0 255.0.0 255.0.0.0 Null00.0 Null0 ip

ip routroute 12.0.0.e 12.0.0.0 255.0.0 255.0.0.0 Null00.0 Null0 ip

ip routroute 13.0.0.e 13.0.0.0 255.0.0 255.0.0.0 Null00.0 Null0

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“Redistrib“Redistribute”ute” command crecommand creates an ASBR router.ates an ASBR router.

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Originated by the ASBR.Originated by the ASBR.

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Describes destination networks external to the OSPF Routing DomainDescribes destination networks external to the OSPF Routing Domain

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Flooded throughout the OSPF AS except to stub and totally stubbyFlooded throughout the OSPF AS except to stub and totally stubby areas

67 67

LSA 5 -

LSA 5 -AS ExterAS External Link nal Link StatesStates

ABR-2 ABR-2

ABR-2R-2# # shoshow w ipip ospospff datdatabaabasese

AS External Link States

AS External Link States <-<-Note, Note, NO ANO Area!rea!

LSA 5 -

LSA 5 - External Networks origiExternal Networks originated by the ASBRnated by the ASBR,, Flooded throughout A.S. except to Stub and Totally Stubby Flooded throughout A.S. except to Stub and Totally Stubby

Link

Link ID ID ADV ADV Router Router Age Age Seq# Seq# Checksum Checksum TagTag 11.0.0.0 11.0.0.0 192.168.1.1 192.168.1.1 1191 1191 0x80000001 0x80000001 0x3FEA 0x3FEA 00 12.0.0.0 12.0.0.0 192.168.1.1 192.168.1.1 1191 1191 0x80000001 0x80000001 0x32F6 0x32F6 00 13.0.0.0 13.0.0.0 192.168.1.1 192.168.1.1 1191 1191 0x80000001 0x80000001 0x2503 0x2503 00

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Link IDLink ID = External Networks= External Networks

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ADV RouterADV Router = = Router ID Router ID of ASBRof ASBR

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NoteNote: : For ABFor ABRs: Rs: There is There is only one only one set of set of “AS Ext“AS External Link ernal Link States”States” inin database summary.

database summary. In other words, In other words, an ABR router wan ABR router will only show one set ofill only show one set of “AS External

“AS External Link States,”Link States,” not one per not one per area.area.

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Bottom line:Bottom line: All Routers should see External networks and the Router ID ofAll Routers should see External networks and the Router ID of ASBR to get there .

ASBR to get there .

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Rick’s reminder: LSARick’s reminder: LSA 55-> -> O O T T H H E E R R networksnetworks 1 1 2 2 3 3 4 4 55 68 68

ABR-2

ABR-2R-2# sho# show ipw ip rouroutete

172.16.0.0/16 is variably subnetted, 4 subnets, 3 masks 172.16.0.0/16 is variably subnetted, 4 subnets, 3 masks O

O IA IA 172.16.51.1/32 172.16.51.1/32 [110/2] [110/2] via via 172.16.1.2, 172.16.1.2, 00:11:44, 00:11:44, FastEthernet0FastEthernet0 O

O 172.16.20.0/24 172.16.20.0/24 [110/782] [110/782] via via 172.16.10.6, 172.16.10.6, 00:12:29, 00:12:29, Serial0Serial0 C

C 172.16.10.4/30 172.16.10.4/30 is is directly directly connected, connected, Serial0Serial0 C

C 172.16.1.0/24 172.16.1.0/24 is is directly directly connected, connected, FastEthernet0FastEthernet0

O E2 11.0.0.0/8 [110/20]

O E2 11.0.0.0/8 [110/20] via 172.16.1.1, 00:11:44, FastEthernet0via 172.16.1.1, 00:11:44, FastEthernet0 O E2 12.0.0.0/8 [110/20]

O E2 12.0.0.0/8 [110/20] via 172.16.1.1, 00:11:44, FastEthernet0via 172.16.1.1, 00:11:44, FastEthernet0 O E2 13.0.0.0/8 [110/20]

O E2 13.0.0.0/8 [110/20] via 172.16.1.1, 00:11:44, FastEthernet0via 172.16.1.1, 00:11:44, FastEthernet0

192.168.3.0/32 is subnetted, 1 subnets 192.168.3.0/32 is subnetted, 1 subnets C

C 192.168.3.1 192.168.3.1 is is directly directly connected, connected, Loopback1Loopback1

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Designated by “E2”Designated by “E2”

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Notice that the cost is 20 for all three routes, we wNotice that the cost is 20 for all three routes, we will see whyill see why later.later.

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It has to do with E2 routes andIt has to do with E2 routes and where the default cost is 20.where the default cost is 20.

–

– Redistribute command (Route Redistribute command (Route Optimization chapter): If a value Optimization chapter): If a value isis notnot specified for the

specified for the metricmetric option, and no value is specified usoption, and no value is specified using theing the default-default- metric

metric command, thecommand, the default metric value is 0, except for OSPF wheredefault metric value is 0, except for OSPF where

the default cost is 20

the default cost is 20..

LSA

69 69 Int

Internernal# al# shoshow iw ipp ospospff datdatabaabasese

Type-5 AS External Link States Type-5 AS External Link States

LSA 5 -

LSA 5 - External Networks External Networks originated by the ASBoriginated by the ASBR,R, Flooded throughout A.S. except to

Flooded throughout A.S. except to Stub and Totally StubbyStub and Totally Stubby

Link

LSA

LSA 5 -5 -

AS EAS External xternal Link Link StatesStates

Inte

Internalrnal# s# show how ipip routroutee

172.16.0.0/16 is variably subnetted, 4 subnets, 3 masks 172.16.0.0/16 is variably subnetted, 4 subnets, 3 masks O

O IA IA 172.16.51.1/32 172.16.51.1/32 [110/783] [110/783] via via 172.16.10.5172.16.10.5, , 00:13:48, 00:13:48, Serial0Serial0 C

C 172.16.20.0/172.16.20.0/ 24 24 is is directly directly connected, connected, FastEthernetFastEthernet 00 C

C 172.16.10.4/172.16.10.4/ 30 30 is is directly directly connected, connected, Serial0Serial0 O

O IA IA 172.16.1.0/2 4 172.16.1.0/24 [110/782] [110/782] via via 172.16.10.5172.16.10.5 , , 00:13:53, 00:13:53, Serial0Serial0 192.168.4.0/

192.168.4.0/32 is 32 is subnetted, 1 subnetssubnetted, 1 subnets C

C 192.168.4.1 192.168.4.1 is is directly directly connected, connected, Loopback0Loopback0

O E2

O E2 11.0.0.0/8 [110/20] via 172.16.10.5, 00:14:41, Serial011.0.0.0/8 [110/20] via 172.16.10.5, 00:14:41, Serial0 O E2

O E2 12.0.0.0/8 [110/20] via 172.16.10.5, 00:14:41, Serial012.0.0.0/8 [110/20] via 172.16.10.5, 00:14:41, Serial0 O E2

O E2 13.0.0.0/8 [110/20] via 172.16.10.5, 00:14:42, Serial013.0.0.0/8 [110/20] via 172.16.10.5, 00:14:42, Serial0

70 70

E1 vs. E2 External Routes

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External routes fall under two categories:External routes fall under two categories: –

– external type 1external type 1 –

– external type 2 (default)external type 2 (default)

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The difference between the two is in the way the cost (metric) of theThe difference between the two is in the way the cost (metric) of the route is being calculated.

route is being calculated.

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The cost of aThe cost of atype 2type 2 route isroute isalways the external costalways the external cost, irrespective of, irrespective of

the interior cost to reach that route.

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AAtype 1type 1cost is thecost is theaddition of the external cost and the internal costaddition of the external cost and the internal cost

used to reach that route.

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A type 1 route is always preferred over a type 2 route for the sameA type 1 route is always preferred over a type 2 route for the same destination.

destination.

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More later…More later…

LSA

71 71

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Using the Using the Multi-area Multi-area OSPF Lab OSPF Lab HandouHandout: t: “Lab 1“Lab 1. –. – OSPFOSPF Normal

Normal Areas”Areas” verify these verify these results.results.

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Look at the link state daLook at the link state database summatabase summary (show ipry (show ip ospfospf

database) commands and the AS External Links States (LSA5s) database) commands and the AS External Links States (LSA5s) for each router.

for each router.

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Also, look at the routing tables for each router.Also, look at the routing tables for each router.

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How many sets of LSA 5s doeHow many sets of LSA 5s does the ABRss the ABRshave in their link state have in their link state

summary

summary database? database? Notice Notice the the ASBRsASBRsentries.entries.

In document UNIVERSIDAD DE LA REPÚBLICA FACULTAD DE VETERINARIA (página 37-40)