Might be a bug on packet tracer. Although daisy-chaining virtual-links is not the best of options, it creates a contiguous area 0 tunnel.   I've gone through your packet tracer file, and in fact, when the ospf process is reloaded, sometimes, 30.0.0.1 will be considered an ABR for the OSPF process (under the show ip ospf border-routers output), that is where the route will be installed on the RIB, however, on both broken and working state scenarios, the required LSA type 1 for area 0 with the ABR information will be there, it will just not install it... (in addition to that, the clear ip ospf process command is also bogus on Packet Tracer, it doesn't cleanup the border-routers information every time).   To avoid going way to far on explanation, lets keep it simple: * The 20.0.0.0/24 route, being a summary route (LSA3), will resolve its next hop by it using its closest ABR based on the OSPF Database information. Who is the ABR originating this route?, it can be either 30.0.0.1 or 20.0.0.1. Based on the OSPF table information, 30.0.0.1 is the closest, however, the OSPF process, sometimes, it doesn't consider it an ABR.   Router#show ip route Codes: L - local, C - connected, S - static, 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, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0/24 [110/4] via 40.0.0.1, 00:19:00, GigabitEthernet0/0 20.0.0.0/24 is subnetted, 1 subnets O IA 20.0.0.0/24 [110/3] via 40.0.0.1, 00:00:10, GigabitEthernet0/0 30.0.0.0/24 is subnetted, 1 subnets O IA 30.0.0.0/24 [110/2] via 40.0.0.1, 00:19:00, GigabitEthernet0/0 40.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 40.0.0.0/24 is directly connected, GigabitEthernet0/0 L 40.0.0.2/32 is directly connected, GigabitEthernet0/0 50.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 50.0.0.0/24 is directly connected, GigabitEthernet0/1 L 50.0.0.1/32 is directly connected, GigabitEthernet0/1 Router#show ip ospf border-routers OSPF Process 1 internal Routing Table Codes: i - Intra-area route, I - Inter-area route i 40.0.0.1 [2] via 40.0.0.1, GigabitEthernet0/0, ABR, Area 0, SPF 2 i 60.0.0.1 [2] via 50.0.0.2, GigabitEthernet0/1, ABR, Area 0, SPF 2 i 30.0.0.1 [3] via 40.0.0.1, GigabitEthernet0/0, ABR, Area 0, SPF 3 ----- It is considered a border router. i 20.0.0.1 [4] via 40.0.0.1, GigabitEthernet0/0, ABR, Area 0, SPF 4 i 40.0.0.1 [1] via 40.0.0.1, GigabitEthernet0/0, ABR, Area 3, SPF 1 i 60.0.0.1 [1] via 50.0.0.2, GigabitEthernet0/1, ABR, Area 4, SPF 1 When the route is not displayed, it is because the 30.0.0.1 is not considered ABR. But for what reason it could not be considered an ABR?  All it needs it is an LSA type 1 from Area 0 (where the tunnel is daisy chained) with the ABR flag on it: (from #show ip ospf data router) LS age: 1555 Options: (No TOS-capability, DC) LS Type: Router Links Link State ID: 30.0.0.1 ------------- 30.0.0.1 LSA Type 1 Advertising Router: 30.0.0.1 LS Seq Number: 80000003 Checksum: 0x7a12 Length: 48 Area Border Router ----------------- It is an ABR Number of Links: 2 Link connected to: a Virtual Link (Link ID) Neighboring Router ID: 20.0.0.1 (Link Data) Router Interface address: 20.0.0.2 Number of TOS metrics: 0 TOS 0 Metrics: 1 Link connected to: a Virtual Link (Link ID) Neighboring Router ID: 40.0.0.1 (Link Data) Router Interface address: 30.0.0.1 Number of TOS metrics: 0 TOS 0 Metrics: 1 The difficult part is that, in both broken and workin state, the database entry is always there, with the ABR flag, so I'm suspecting an issue with packet tracer processing that ABR status from time to time.   I would suggest to try reproducing this scenario on GNS3, Eve-ng or VIRL instead of PT because of its bugs and limitations.   ... View more

You are likely hitting a packet tracer bug. Your configuration is fine. Tried it on VIRL and it works: ciscoasa# show xlate 1 in use, 1 most used Flags: D - DNS, e - extended, I - identity, i - dynamic, r - portmap, s - static, T - twice, N - net-to-net ICMP PAT from inside:10.10.10.2/0 to outside:100.100.100.2/25215 flags ri idle 0:00:00 timeout 0:00:30 ciscoasa# show xlate 2 in use, 2 most used Flags: D - DNS, e - extended, I - identity, i - dynamic, r - portmap, s - static, T - twice, N - net-to-net ICMP PAT from inside:10.10.10.2/0 to outside:100.100.100.2/25215 flags ri idle 0:00:09 timeout 0:00:30 ICMP PAT from inside:10.16.18.10/1 to outside:100.100.100.2/1 flags ri idle 0:00:00 timeout 0:00:30 ciscoasa# Int config: ASA Version 9.9(2) ! hostname ciscoasa enable password $sha512$5000$LIuEniMbWtxU/3PSRiZerg==$UYUOp3RHITaZuEGhJOKe8Q== pbkdf2 names ! interface GigabitEthernet0/0 nameif outside security-level 0 ip address 100.100.100.2 255.255.255.0 ! interface GigabitEthernet0/1 nameif inside security-level 100 ip address 10.10.10.1 255.255.255.0 ! Router 2 has a loopack with your LAN subnet 10.16.18.0/24 Router 1 has a loopback with 8.8.8.8 LAN segments are the same.   ... View more

R3 will not receive the query (R2 will queue it, but won't send it to R3) because R2 already knows about its stub router status from the neighbor information: R2#show ip eigrp neighbors de EIGRP-IPv4 Neighbors for AS(1) H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 1 23.23.23.3 Gi2/0 10 00:01:13 17 102 0 29 Version 11.0/2.0, Retrans: 1, Retries: 0, Prefixes: 1 Topology-ids from peer - 0 Stub Peer Advertising (CONNECTED SUMMARY ) Routes -------------- neighbor is stub. And yes, R2 will forget everything about that /32, it is no longer enabled, neither considered connected interface on its routing table ... View more

For Areas to be inter-connected in OSPF, Area 0 is needed, mainly because of the concept of an ABR. Starting from the ABR concept, it is usually mistaken that an ABR is just an OSPF router which has interfaces in two or more different areas, however, the true definition of an ABR is for a router which has an Area 0 interface and other area or areas attached to it. If no Area 0 exists on the router (in the form of a network statement or Virtual Link), such router is not considered ABR. ABRs do a quite important job in regards of SPF calculation. Starting from the fact that LSA type 1 and LSA type 2 are the LSAs that include enough information for SPF to determine a loop-free calculation path, these are expected to be flooded inside an area, but how are these flooded towards other areas? ABRs take that information and create an LSA type 3 which basically says "no need to calculate complex LSA type 1 structures, for all the routers in my area, you can just reach that prefix destination towards me" Taking that in consideration, a router siting between Area 1 and Area 2 is in fact, no ABR, no LSA type 1 to LSA type 3 "conversion" does ever exist. LSA Type 1s generated in Area 1 will not be passed through Area 2 and vice versa, because that intermediatte router is no ABR. In fact, if you create a loopback for Area 0 in that router, then it becomes ABR and then, now it can generate such LSAs. For the last question. (Area7)(RTRX)----------------(Area 7)(RTRA)(Area 6)----------- (Area6)(RTRB)(Area0) If this is similar to what you want to achieve, then this is a Virtual-Link case use scenario, RTA is attached to Area 7 and 6 but not to Area 0. In summary, RTRB is an ABR while RTRA is not, no LSA3 generation will be done on RTRA. RTRX and RTRB need to establish a tunnel in between in the form of a virtual-link in OSPF, a virtual-link is by nature, a p2p tunnel in area 0 with no periodic hello between them. This creates a virtual path from a non ABR router to a true ABR router, allowing routes (LSAs) to be propagated. ... View more