////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////// 1. Created a stub area 2. Looked at how traceroute works with stub areas 3. Examined how the LSAs are effected by a stub area (look at the database command) 4. How to create "totally stubby areas" Reference Diagram: diag_stub1.ps ////////////////////////////////////////////////////////////////////////// ////////////////////////////////////////////////////////////////////////// Assumptions of the experiment ============================= The idea was to test stub areas and - test if the stub area is prevented from acting as a transit area. - check whether type 4 and type 5 LSAs are blocked from reaching stub area - test if type 3 LSAs are blocked in totally stubby areas. Configuration for a stub area ============================== An area becomes a stub area when it has a single exit point or when routing to the outside does not have to take an optimal path. Stub areas do not allow any external routes to be flooded through them and routing from a stub area to the outside world is based only on default routes. We configured OSPF on the six routers with 3 areas (Area 0, Area1 and Area2) as shown in diag2.txt. Area 0 is the backbone area, as usual, and area 1 was configured to be the stub area. Dexter : ASBR in Area 0 (Backbone area) Radia : ABR (Area 0 and Area 1) Mrhorse : ABR (Area 0 and Area 2) Yakov : Internal router for Area 2 Big-baby: Internal router for Area 2 After running OSPF in all the 3 areas, we used the following command in order to configure area 1 as the stub: >area area-id stub [no-summary] area-id - identifies the stub area. This is either a decimal number or an IP address no-summary - an option used in order to shut off summary link advertisements going into the stub area In order to disable the stub area function, the same command is used with a 'no' prepended to it. For eg. "area area-id stub [no-summary]" The configuration for the different routers is shown below. (NOTE the area command that enables area 1 to be a stub area. This command is necessary for all the routers that have an interface in that area) DEXTER ====== dexter#config t Enter configuration commands, one per line. End with CNTL/Z. dexter(config)#router ospf 100 dexter(config-router)#network 131.252.215.4 0.0.0.0 area 0 dexter(config-router)#network 131.252.215.33 0.0.0.0 area 0 dexter(config)#default-information originate metric-type 1 dexter(config-router)#^Z dexter# RADIA ===== radia#config t Enter configuration commands, one per line. End with CNTL/Z. radia(config)#router ospf 100 radia(config-router)#network 131.252.215.34 0.0.0.0 area 0 radia(config-router)#network 131.252.215.49 0.0.0.0 area 1 radia(config-router)#area 1 stub radia(config-router)#^Z radia# MRHORSE ======= mrhorse#config t Enter configuration commands, one per line. End with CNTL/Z. mrhorse(config)#router ospf 100 mrhorse(config-router)#network 131.252.215.35 0.0.0.0 area 0 mrhorse(config-router)#network 131.252.215.67 0.0.0.0 area 2 mrhorse(config-router)#^Z mrhorse# TONY ==== tony#config t Enter configuration commands, one per line. End with CNTL/Z. tony(config)#router ospf 100 tony(config-router)#network 131.252.215.50 0.0.0.0 area 1 tony(config-router)#network 131.252.215.65 0.0.0.0 area 2 tony(config-router)#area 1 stub tony(config-router)#^Z tony#sh YAKOV ===== yakov#config t Enter configuration commands, one per line. End with CNTL/Z. yakov(config)#router ospf 100 yakov(config-router)#network 131.252.215.66 0.0.0.0 area 2 yakov(config-router)#^Z yakov(config-router)# yakov# BIG-BABY ======== big-baby#config t Enter configuration commands, one per line. End with CNTL/Z. big-baby(config)#router ospf 100 big-baby(config-router)#network 0.0.0.0 0.0.0.0 131.252.215.82 area 2 big-baby(config-router)#^Z big-baby# ////////////////////////////////////////////////////////////////////////// Routes taken by packets after creating the stub (using TRACEROUTE command) ========================================================================== We examined the routes taken by packets after the stub area was created. The path from Dexter to Yakov and Big-Baby can go from Radia and Tony OR through Mrhorse. Mrhorse has a higher default cost (of 10) than Radia and Tony so if area 1 was NOT a stub, then all packets would go from Dexter to Yakov through Radia and Tony. However, when area 1 is configured as a stub area that cannot allow packets to pass through, we see that all the packets from Dexter to Yakov and Big-baby go through the higher cost path i.e. through Mrhorse. Each router was tested by running traceroute from that router to all interfaces of other routers DEXTER ------ a. FROM Dexter TO Radia (directly connected - one hop away) b. FROM Dexter TO Mrhorse (directly connected - one hop away) c. FROM Dexter TO Tony (goes through RADIA since the route is INTO Stub area) Tracing the route to tony.cs.pdx.edu (131.252.215.50) 1 radia.cs.pdx.edu (131.252.215.34) 0 msec 4 msec 0 msec 2 tony.cs.pdx.edu (131.252.215.50) 4 msec * 0 msec Tracing the route to 131.252.215.65 1 mrhorse.cat.pdx.edu (131.252.215.35) 4 msec 4 msec 0 msec 2 131.252.215.65 4 msec * 0 msec d. FROM Dexter TO Yakov (through MRHORSE even though it's a higher cost path) Tracing the route to yakov.cs.pdx.edu (131.252.215.66) 1 mrhorse.cat.pdx.edu (131.252.215.35) 0 msec 0 msec 4 msec 2 yakov.cs.pdx.edu (131.252.215.66) 4 msec * 0 msec Tracing the route to 131.252.215.81 1 mrhorse.cat.pdx.edu (131.252.215.35) 0 msec 4 msec 4 msec 2 yakov.cs.pdx.edu (131.252.215.66) 0 msec * 0 msec e. FROM Dexter TO Big-baby (through MRHORSE-YAKOV, the higher cost path) Tracing the route to big-baby.cs.pdx.edu (131.252.215.82) 1 mrhorse.cat.pdx.edu (131.252.215.35) 0 msec 0 msec 4 msec 2 yakov.cs.pdx.edu (131.252.215.66) 4 msec 4 msec 0 msec 3 big-baby.cs.pdx.edu (131.252.215.82) 4 msec * 0 msec RADIA ----- a. FROM Radia TO Dexter (directly connected - one hop away) b. FROM Radia TO Tony (directly connected - one hop away) c. Radia TO Mrhorse (directly connected - one hop away) d. FROM Radia TO Yakov (through MRHORSE even though it's a higher cost path) Tracing the route to yakov.cs.pdx.edu (131.252.215.66) 1 mrhorse.cat.pdx.edu (131.252.215.35) 4 msec 4 msec 0 msec 2 yakov.cs.pdx.edu (131.252.215.66) 4 msec * 0 msec Tracing the route to 131.252.215.81 1 mrhorse.cat.pdx.edu (131.252.215.35) 0 msec 4 msec 4 msec 2 yakov.cs.pdx.edu (131.252.215.66) 4 msec * 0 msec e. FROM Radia TO Big-baby (through MRHORSE-YAKOV even though it's a higher cost path) Tracing the route to big-baby.cs.pdx.edu (131.252.215.82) 1 mrhorse.cat.pdx.edu (131.252.215.35) 0 msec 4 msec 4 msec 2 yakov.cs.pdx.edu (131.252.215.66) 0 msec 0 msec 4 msec 3 big-baby.cs.pdx.edu (131.252.215.82) 4 msec * 0 msec TONY ---- a. FROM Tony TO Radia (directly connected - one hop away) b. FROM Tony TO Yakov (directly connected - one hop away) c. FROM Tony TO MrHorse Tracing the route to mrhorse.cat.pdx.edu (131.252.215.35) 1 131.252.215.49 0 msec 0 msec 0 msec 2 mrhorse.cat.pdx.edu (131.252.215.35) 4 msec * 0 msec Tracing the route to mrhorse.cat.pdx.edu (131.252.215.67) 1 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec * 0 msec The interesting point to note is the difference in routing for two different interfaces of the same router. The interface that is directly connected is reached in one hop but the interface that is not directly connected is routed through Radia. d. FROM Tony TO Dexter (through RADIA since it's going OUT of the stub) Tracing the route to dexter.cs.pdx.edu (131.252.215.4) 1 131.252.215.49 4 msec 0 msec 4 msec 2 131.252.215.33 0 msec * 0 msec Tracing the route to 131.252.215.33 1 131.252.215.49 0 msec 4 msec 0 msec 2 131.252.215.33 4 msec * 0 msec e. FROM Tony TO Big-baby (through YAKOV since it's going OUT of the stub) Tracing the route to big-baby.cs.pdx.edu (131.252.215.82) 1 yakov.cs.pdx.edu (131.252.215.66) 0 msec 4 msec 0 msec 2 big-baby.cs.pdx.edu (131.252.215.82) 4 msec * 0 msec MRHORSE ------- a. FROM Mrhorse TO Dexter (directly connected - one hop away) b. FROM Mrhorse TO Radia (directly connected - one hop away) c. FROM Mrhorse TO Yakov (directly connected - one hop away) d. FROM Mrhorse TO Tony Tracing the route to tony.cs.pdx.edu (131.252.215.50) 1 radia.cs.pdx.edu (131.252.215.34) 4 msec 0 msec 0 msec 2 tony.cs.pdx.edu (131.252.215.50) 4 msec * 0 msec Tracing the route to 131.252.215.65 1 131.252.215.65 4 msec * 0 msec NOTE: The route to the interface that is directly connected is one hop while the route to the indirectly connected interface goes through radia. e. FROM Mrhorse TO Big-Baby (through YAKOV) Tracing the route to big-baby.cs.pdx.edu (131.252.215.82) 1 yakov.cs.pdx.edu (131.252.215.66) 4 msec 4 msec 4 msec 2 big-baby.cs.pdx.edu (131.252.215.82) 8 msec * 4 msec YAKOV ----- a. FROM Yakov TO Mrhorse (directly connected - one hop away) b. FROM Yakov TO Big-baby (directly connected - one hop away) c. FROM Yakov TO Dexter (through MRHORSE, the higher cost path) Tracing the route to dexter.cs.pdx.edu (131.252.215.4) 1 mrhorse.cat.pdx.edu (131.252.215.67) 0 msec 4 msec 0 msec 2 131.252.215.33 0 msec * 0 msec Tracing the route to 131.252.215.33 1 131.252.215.67 4 msec 4 msec 0 msec 2 131.252.215.33 4 msec * 0 msec d. FROM Yakov TO Radia (through MRHORSE, the higher cost path) Tracing the route to radia.cs.pdx.edu (131.252.215.34) 1 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec 4 msec 0 msec 2 radia.cs.pdx.edu (131.252.215.34) 4 msec * 0 msec Tracing the route to 131.252.215.49 1 131.252.215.67 4 msec 0 msec 4 msec 2 131.252.215.34 4 msec * 0 msec e. FROM Yakov TO Tony Tracing the route to tony.cs.pdx.edu (131.252.215.50) 1 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec 0 msec 0 msec 2 radia.cs.pdx.edu (131.252.215.34) 4 msec 0 msec 4 msec 3 tony.cs.pdx.edu (131.252.215.50) 0 msec * 0 msec Tracing the route to 131.252.215.65 1 131.252.215.65 4 msec 0 msec 4 msec Note: The route to the interface that is directly connected is one hop away but the route to the interface not directly connected is through mrhorse and Radia. BIG-BABY -------- a. FROM Big-baby TO Yakov (directly connected - one hop away) b. FROM Big-baby TO Dexter (through YAKOV-MRHORSE, the higher cost path) Tracing the route to dexter.cs.pdx.edu (131.252.215.4) 1 131.252.215.81 0 msec 4 msec 0 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec 0 msec 0 msec 3 131.252.215.33 0 msec * 0 msec Tracing the route to 131.252.215.33 1 131.252.215.81 0 msec 0 msec 4 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec 4 msec 4 msec 3 131.252.215.33 4 msec * 4 msec c. FROM Big-baby TO Radia (through YAKOV-MRHORSE, the higher cost path) Tracing the route to radia.cs.pdx.edu (131.252.215.34) 1 131.252.215.81 0 msec 0 msec 4 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec 4 msec 4 msec 3 radia.cs.pdx.edu (131.252.215.34) 4 msec * 0 msec Tracing the route to 131.252.215.49 1 131.252.215.81 0 msec 0 msec 4 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec 4 msec 4 msec 3 radia.cs.pdx.edu (131.252.215.34) 4 msec * 0 msec d. FROM Big-baby TO Tony Tracing the route to tony.cs.pdx.edu (131.252.215.50) 1 131.252.215.81 0 msec 96 msec 0 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 0 msec 4 msec 0 msec 3 radia.cs.pdx.edu (131.252.215.34) 0 msec 0 msec 4 msec 4 tony.cs.pdx.edu (131.252.215.50) 4 msec * 0 msec Tracing the route to 131.252.215.65 1 131.252.215.81 4 msec 4 msec 0 msec 2 131.252.215.65 4 msec * 0 msec NOTE: The route to the interface indirectly connected to Yakov is longer while the route to the interface directly connected to Yakov is only 2 hops. e. FROM Big-baby TO Mrhorse (through YAKOV) Tracing the route to mrhorse.cat.pdx.edu (131.252.215.35) 1 131.252.215.81 0 msec 0 msec 4 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec * 0 msec Tracing the route to mrhorse.cat.pdx.edu (131.252.215.67) 1 131.252.215.81 0 msec 0 msec 0 msec 2 mrhorse.cat.pdx.edu (131.252.215.67) 4 msec * 0 msec ////////////////////////////////////////////////////////////////////////// The effect of stub area on the LSAs =================================== The results of the "show ip ospf database" command are shown below for every router. We compared the results with the database results obtained for the same configuration but without a stub area. DEXTER (AS EXPECTED) ------ Comparison with database without the stub area: - The Net Link States in Area 0 show advertising router as 131.252.215.67 (mrhorse). Without the stub area, the adv Router is 131.252.215.33 (Dexter) dexter#sh ip ospf database OSPF Router with ID (131.252.215.33) (Process ID 100) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.33 131.252.215.33 1441 0x80000005 0xF703 2 131.252.215.49 131.252.215.49 1746 0x80000003 0x66C0 1 131.252.215.67 131.252.215.67 1752 0x80000003 0xF503 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.35 131.252.215.67 1441 0x80000002 0x6925 Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.48 131.252.215.49 307 0x80000005 0xE94B 131.252.215.64 131.252.215.67 1885 0x80000001 0x3FCE 131.252.215.80 131.252.215.67 1885 0x80000001 0xA854 Summary ASB Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.67 131.252.215.67 1893 0x80000001 0xEA3A Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 1463 0x80000001 0x7FD6 100 RADIA ----- Comparison with database without the stub area: - The Net Link States in Area 0 show advertising router as 131.252.215.67 (mrhorse). Without the stub area, the adv Router is 131.252.215.33 (Dexter) - Router Link States (Area 1) , no longer show any LSAs advertised by 131.252.215.67 (mrhorse), 131.252.215.81 (Yakov) and 131.252.215.82 (big-baby). This three are present in the database without stub area. - Net Link States (Area 1) show that only 131.252.215.65 (Tony) is the adv Router. In the original database, 131.252.215.49 (Radia) and 131.252.215.67 (mrhorse) are sending this out and Tony does not send out anything. Tony has been selected as an DR for the stub area. - All Summary Net Link States (Type 3) for area 1 show only Radia as the adv router. In the original database without the stub area, mrhorse is also present. - We cannot see any type 4 LSAs (Summary ASB Link States)going into Area 1 (the stub area). In the original database without stub area, type 4 LSAs are present - Surprisingly, type 5 LSA is present but we guess it is present because Radia is directly connected to the backbone and Type 5 comes in for Area 0. radia#show ip ospf database OSPF Router with ID (131.252.215.49) (Process ID 100) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.33 131.252.215.33 1559 0x80000005 0xF703 2 131.252.215.49 131.252.215.49 1863 0x80000003 0x66C0 1 131.252.215.67 131.252.215.67 47 0x80000004 0xF304 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.35 131.252.215.67 1558 0x80000002 0x6925 Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.48 131.252.215.49 423 0x80000005 0xE94B 131.252.215.64 131.252.215.67 48 0x80000002 0x3DCF 131.252.215.80 131.252.215.67 48 0x80000002 0xA655 Summary ASB Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.67 131.252.215.67 48 0x80000002 0xE83B Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.49 131.252.215.49 451 0x80000004 0xEB1E 1 131.252.215.65 131.252.215.65 451 0x80000006 0xF1F5 1 Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 131.252.215.50 131.252.215.65 447 0x80000002 0x7290 Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 0.0.0.0 131.252.215.49 456 0x80000001 0x1C98 131.252.215.0 131.252.215.49 456 0x80000002 0x99DF 131.252.215.32 131.252.215.49 456 0x80000002 0xAE9B 131.252.215.64 131.252.215.49 456 0x80000002 0xD14E 131.252.215.80 131.252.215.49 456 0x80000002 0x3BD3 Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 1598 0x80000001 0x7FD6 100 TONY ---- Comparison with database without the stub area: - Router Link States (Area 1) , no longer show any LSAs advertised by 131.252.215.67 (mrhorse), 131.252.215.81 (Yakov) and 131.252.215.82 (big-baby). This three are present in the database without stub area. - Net Link States (Area 1) show that only 131.252.215.65 (Tony) is the adv Router. In the original database, 131.252.215.49 (Radia) and 131.252.215.67 (mrhorse) are sending this out and Tony does not send out anything. Tony has been selected as an DR for the stub area. - All Summary Net Link States (Type 3) for area 1 show only Radia as the adv router. In the original database without the stub area, mrhorse is also present. - We cannot see any type 4 LSAs (Summary ASB Link States)going into Area 1 In the original database without stub area, type 4 LSAs are present - Surprisingly, type 5 LSA is present but we guess it is present because mrhorse is announcing it to Tony for Area 2. tony#sh ip ospf data OSPF Router with ID (131.252.215.65) (Process ID 100) Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.49 131.252.215.49 548 0x80000004 0xEB1E 1 131.252.215.65 131.252.215.65 548 0x80000006 0xF1F5 1 Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 131.252.215.50 131.252.215.65 543 0x80000002 0x7290 Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 0.0.0.0 131.252.215.49 553 0x80000001 0x1C98 131.252.215.0 131.252.215.49 553 0x80000002 0x99DF 131.252.215.32 131.252.215.49 553 0x80000002 0xAE9B 131.252.215.64 131.252.215.49 553 0x80000002 0xD14E 131.252.215.80 131.252.215.49 553 0x80000002 0x3BD3 Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.65 131.252.215.65 1048 0x80000003 0x4D7C 1 131.252.215.67 131.252.215.67 174 0x80000003 0xEECA 1 131.252.215.81 131.252.215.81 142 0x80000005 0x80C1 2 131.252.215.82 131.252.215.82 920 0x80000003 0x504D 1 Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.66 131.252.215.81 1065 0x80000002 0x71AF 131.252.215.82 131.252.215.82 920 0x80000002 0xFAC3 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.0 131.252.215.67 1682 0x80000001 0x6BF1 131.252.215.32 131.252.215.67 174 0x80000004 0x7AB0 131.252.215.48 131.252.215.67 551 0x80000001 0xE933 Summary ASB Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.33 131.252.215.67 1682 0x80000001 0xC25A Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 1722 0x80000001 0x7FD6 100 MRHORSE (AS EXPECTED) ------- Comparison with database without the stub area: - The Net Link States in Area 0 show advertising router as 131.252.215.67 (mrhorse). Without the stub area, the adv Router is 131.252.215.33 (Dexter) mrhorse#sh ip ospf data OSPF Router with ID (131.252.215.67) (Process ID 100) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.33 131.252.215.33 599 0x80000006 0xF504 2 131.252.215.49 131.252.215.49 876 0x80000004 0x64C1 1 131.252.215.67 mrhorse.cat.pdx 1026 0x80000004 0xF304 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.35 mrhorse.cat.pdx 531 0x80000003 0x6726 Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.48 131.252.215.49 1404 0x80000005 0xE94B 131.252.215.64 mrhorse.cat.pdx 1027 0x80000002 0x3DCF 131.252.215.80 mrhorse.cat.pdx 1027 0x80000002 0xA655 Summary ASB Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.67 mrhorse.cat.pdx 1027 0x80000002 0xE83B Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.65 131.252.215.65 1924 0x80000003 0x4D7C 1 131.252.215.67 mrhorse.cat.pdx 1035 0x80000003 0xEECA 1 131.252.215.81 131.252.215.81 1004 0x80000005 0x80C1 2 131.252.215.82 big-baby.cs.pdx 1782 0x80000003 0x504D 1 Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.66 131.252.215.81 33 0x80000003 0x6FB0 131.252.215.82 big-baby.cs.pdx 1782 0x80000002 0xFAC3 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.0 mrhorse.cat.pdx 540 0x80000002 0x69F2 131.252.215.32 mrhorse.cat.pdx 1035 0x80000004 0x7AB0 131.252.215.48 mrhorse.cat.pdx 1418 0x80000001 0xE933 Summary ASB Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.33 mrhorse.cat.pdx 546 0x80000002 0xC05B Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 614 0x80000002 0x7DD7 100 YAKOV (AS EXPECTED) ----- yakov#sh ip ospf data OSPF Router with ID (131.252.215.81) (Process ID 100) Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.65 131.252.215.65 315 0x80000004 0x4B7D 1 131.252.215.67 131.252.215.67 1378 0x80000003 0xEECA 1 131.252.215.81 131.252.215.81 1345 0x80000005 0x80C1 2 131.252.215.82 131.252.215.82 323 0x80000004 0x4E4E 1 Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.66 131.252.215.81 373 0x80000003 0x6FB0 131.252.215.82 131.252.215.82 323 0x80000003 0xF8C4 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.0 131.252.215.67 883 0x80000002 0x69F2 131.252.215.32 131.252.215.67 1378 0x80000004 0x7AB0 131.252.215.48 131.252.215.67 1755 0x80000001 0xE933 Summary ASB Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.33 131.252.215.67 889 0x80000002 0xC05B Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 958 0x80000002 0x7DD7 100 BIG-BABY (AS EXPECTED) -------- big-baby#sh ip ospf data OSPF Router with ID (131.252.215.82) (Process ID 100) Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.65 131.252.215.65 592 0x80000004 0x4B7D 1 131.252.215.67 131.252.215.67 1655 0x80000003 0xEECA 1 131.252.215.81 131.252.215.81 1622 0x80000005 0x80C1 2 131.252.215.82 131.252.215.82 598 0x80000004 0x4E4E 1 Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.66 131.252.215.81 650 0x80000003 0x6FB0 131.252.215.82 131.252.215.82 598 0x80000003 0xF8C4 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.0 131.252.215.67 1160 0x80000002 0x69F2 131.252.215.32 131.252.215.67 1655 0x80000004 0x7AB0 131.252.215.48 131.252.215.67 127 0x80000002 0xE734 Summary ASB Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.33 131.252.215.67 1161 0x80000002 0xC05B AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 1230 0x80000002 0x7DD7 100 EFFECT OF THE STUB AREA ON THE IP ROUTES ======================================== TONY - Note that the extrenal route (O E1) does not show up. ---- tony#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR T - traffic engineered route Gateway of last resort is 131.252.215.49 to network 0.0.0.0 131.252.0.0/16 is variably subnetted, 5 subnets, 2 masks O IA 131.252.215.32/28 [110/2] via 131.252.215.49, FastEthernet0/0 C 131.252.215.48/28 is directly connected, FastEthernet0/0 O IA 131.252.215.0/27 [110/3] via 131.252.215.49, FastEthernet0/0 C 131.252.215.64/28 is directly connected, FastEthernet0/1 O 131.252.215.80/28 [110/2] via 131.252.215.66, FastEthernet0/1 O*IA 0.0.0.0/0 [110/2] via 131.252.215.49, FastEthernet0/0 ////////////////////////////////////////////////////////////////////////// How to create a totally stubby area =================================== A totally stubby area is one that blocks all external and summary routes from going into the area and allows only intra-area routes and the default route to be injected into the area. This is done by using the no-summary option in the "area area-id stub [no-summary]" command. The changes in the LSAs for Tony and Radia are shown. Using the no-summary option shuts off Type three LSAs into the stub area. Only the default route is sent to the stub area in type 3 LSA for both Tony and Radia. After running OSPF in all the 3 areas and configuring area 1 as stub area, we used the following command on Radia and Tony to configure area 1 as a Totally Stbby Area. RADIA ===== radia#config t Enter configuration commands, one per line. End with CNTL/Z. radia(config)#router ospf 100 radia(config-router)#area 1 stub no-summary radia(config-router)#^Z radia# TONY ==== tony#config t Enter configuration commands, one per line. End with CNTL/Z. tony(config)#router ospf 100 tony(config-router)#area 1 stub no-summary tony(config-router)#^Z tony#sh In both Radia and Tony, for area 1, we see that the Summary Net Link States (Type 3) are now absent. RADIA ----- radia#sh ip ospf data OSPF Router with ID (131.252.215.49) (Process ID 100) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.33 131.252.215.33 1547 0x80000007 0xF305 2 131.252.215.49 131.252.215.49 1808 0x80000005 0x62C2 1 131.252.215.67 131.252.215.67 1972 0x80000005 0xF105 1 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.35 131.252.215.67 1450 0x80000004 0x6527 Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.48 131.252.215.49 439 0x80000001 0xF147 131.252.215.64 131.252.215.67 1973 0x80000003 0x3BD0 131.252.215.80 131.252.215.67 1973 0x80000003 0xA456 Summary ASB Link States (Area 0) Link ID ADV Router Age Seq# Checksum 131.252.215.67 131.252.215.67 1973 0x80000003 0xE63C Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.49 131.252.215.49 448 0x8000000C 0xD131 1 131.252.215.50 131.252.215.50 480 0x80000002 0xE02A 1 Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 131.252.215.49 131.252.215.49 448 0x80000001 0x4CD7 Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 0.0.0.0 131.252.215.49 869 0x80000004 0x169B Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 1552 0x80000003 0x7BD8 100 TONY ---- tony#sh ip os data OSPF Router with ID (131.252.215.50) (Process ID 100) Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.49 131.252.215.49 380 0x8000000C 0xD131 1 131.252.215.50 131.252.215.50 411 0x80000002 0xE02A 1 Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 131.252.215.49 131.252.215.49 380 0x80000001 0x4CD7 Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 0.0.0.0 131.252.215.49 800 0x80000004 0x169B Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 131.252.215.50 131.252.215.50 10 0x80000003 0x3EA9 1 131.252.215.65 131.252.215.65 831 0x80000005 0x497E 1 131.252.215.67 131.252.215.67 1914 0x80000004 0xECCB 1 131.252.215.81 131.252.215.81 1930 0x80000006 0x7EC2 2 131.252.215.82 131.252.215.82 1074 0x80000005 0x4C4F 1 Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.66 131.252.215.81 16 0x80000006 0x9695 131.252.215.82 131.252.215.82 1075 0x80000004 0xF6C5 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.0 131.252.215.67 1392 0x80000003 0x67F3 131.252.215.32 131.252.215.67 1914 0x80000005 0x78B1 131.252.215.48 131.252.215.67 447 0x80000001 0xE933 Summary ASB Link States (Area 2) Link ID ADV Router Age Seq# Checksum 131.252.215.33 131.252.215.67 1392 0x80000003 0xBE5C Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 0.0.0.0 131.252.215.33 1491 0x80000003 0x7BD8 100 //////////////////////////////////////////////////////////////////////////