OSPF over Frame Relay. ADJ is formed, LSA is recevied, but no entry in routing table

San Jose, California
August 26, 2013 10:26pm CST
Question: R13 is a HUB and R14, R15, R16 are Cisco 2921 price Cisco 2921 price spoke routers. R13 is configured as point-to-multipoint non-broadcast R13#sh run inter s 2/0 Building configuration... Current configuration : 183 bytes ! interface Serial2/0 ip address 10.5.1.13 255.255.255.0 encapsulation frame-relay ip ospf network point-to-multipoint non-broadcast ip ospf 1 area 5 serial restart-delay 0 end R13# R14 is configured as point-to-multipoint non-broadcast too, and OSPF routing is running good in R14: R14#sh run inter s 1/0 Building configuration... Current configuration : 183 bytes ! interface Serial1/0 ip address 10.5.1.14 255.255.255.0 encapsulation frame-relay ip ospf network point-to-multipoint non-broadcast ip ospf 1 area 5 serial restart-delay 0 end R14# R14#sh ip route ospf 17.0.0.0/24 is subnetted, 1 subnets O IA 17.0.0.0 [110/76] via 10.5.1.13, 00:39:13, Serial1/0 O IA 192.168.12.0/24 [110/66] via 10.5.1.13, 00:39:13, Serial1/0 .... However, I R15's frame relay is using the default ospf type (non-broadcast), but no entry in it's routing table, even it has LSA. I know it should be the same OSPF network type in all the routers interfaces. I am just wondering how the things work: R15#sh run inter s 1/0 Building configuration... Current configuration : 132 bytes ! interface Serial1/0 ip address 10.5.1.15 255.255.255.0 encapsulation frame-relay ip ospf 1 area 5 serial restart-delay 0 end R15# R15#sh ip os nei Neighbor ID Pri State Dead Time Address Interface 192.168.132.13 1 FULL/BDR 00:01:55 10.5.1.13 Serial1/0 R15# R15#sh ip route Codes: 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 i - IS-IS, su - IS-IS summary, 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 C 10.5.1.0 is directly connected, Serial1/0 R15# R15#sh ip os database OSPF Router with ID (10.5.1.15) (Process ID 1) Router Link States (Area 5) Link ID ADV Router Age Seq# Checksum Link count 10.5.1.14 10.5.1.14 651 0x80000007 0x001E4D 2 10.5.1.15 10.5.1.15 931 0x80000003 0x00AEC6 1 10.5.1.16 10.5.1.16 357 0x80000003 0x0098DB 1 192.168.132.13 192.168.132.13 779 0x80000004 0x009CDF 4 Net Link States (Area 5) Link ID ADV Router Age Seq# Checksum 10.5.1.15 10.5.1.15 931 0x80000002 0x0009D7 Summary Net Link States (Area 5) Link ID ADV Router Age Seq# Checksum 10.1.1.0 192.168.132.13 1035 0x80000002 0x0062C7 10.2.18.0 192.168.132.13 1035 0x80000002 0x00A472 10.2.118.0 192.168.132.13 1035 0x80000002 0x005E53 10.3.49.0 192.168.132.13 1035 0x80000002 0x0038BF Answer: John is right the root cause of the behaviour you see is the mismatch in OSPF network type between R15 and the other routers in segment more specifically R13. When R15 runs SPF it detects the mismatch or simply by examining the OSPF hello packets received by R13 not listing R15 as DR and R13 as BDR as it happens on OSPF hello generated by R15 itself. After detecting the OSPF network type mismatch the local node does not use the LSAs received from the neighbor(s) with different network type. Let's see this as a safety measure of the protocol itself. Cisco 1900 sereis router Cisco 1900 sereis router
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