Small step toward , repaired the ospf adjency between the Nexus pair. They see each other (int vlan 2 down..) But the CoreAB OSPF process doesn't see the Nexus switches. TEST_N5k-primary# sh ip ospf neighbor OSPF Process ID 1 VRF default Total number of neighbors: 1 Neighbor ID Pri State Up Time Address Interface 220.127.116.11 1 FULL/BDR 00:09:39 10.58.16.2 Vlan2 TEST_N5k-secondary# sh ip ospf neighbor OSPF Process ID 1 VRF default Total number of neighbors: 1 Neighbor ID Pri State Up Time Address Interface 18.104.22.168 1 FULL/DR 00:10:36 10.58.16.1 Vlan2 CoreAB TEST_CoreAB#sh ip ospf Routing Process "ospf 1" with ID 192.168.11.246 Start time: 00:04:22.185, Time elapsed: 00:14:05.537 Supports only single TOS(TOS0) routes Supports opaque LSA Supports Link-local Signaling (LLS) Supports area transit capability Supports NSSA (compatible with RFC 3101) Supports Database Exchange Summary List Optimization (RFC 5243) Event-log enabled, Maximum number of events: 1000, Mode: cyclic It is an autonomous system boundary router Redistributing External Routes from, static, includes subnets in redistribution Router is not originating router-LSAs with maximum metric Initial SPF schedule delay 5000 msecs Minimum hold time between two consecutive SPFs 10000 msecs Maximum wait time between two consecutive SPFs 10000 msecs Incremental-SPF disabled Minimum LSA interval 5 secs Minimum LSA arrival 1000 msecs LSA group pacing timer 240 secs Interface flood pacing timer 33 msecs Retransmission pacing timer 66 msecs EXCHANGE/LOADING adjacency limit: initial 300, process maximum 300 Number of external LSA 0. Checksum Sum 0x000000 Number of opaque AS LSA 0. Checksum Sum 0x000000 Number of DCbitless external and opaque AS LSA 0 Number of DoNotAge external and opaque AS LSA 0 Number of areas in this router is 1. 1 normal 0 stub 0 nssa Number of areas transit capable is 0 External flood list length 0 IETF NSF helper support enabled Cisco NSF helper support enabled Reference bandwidth unit is 100 mbps Area BACKBONE(0) (Inactive) Number of interfaces in this area is 1 Area has no authentication SPF algorithm last executed 00:13:11.570 ago SPF algorithm executed 2 times Area ranges are Number of LSA 1. Checksum Sum 0x00BF42 Number of opaque link LSA 0. Checksum Sum 0x000000 Number of DCbitless LSA 0 Number of indication LSA 0 Number of DoNotAge LSA 0 Flood list length 0 TEST_CoreAB#sh ip ospf route OSPF Router with ID (192.168.11.246) (Process ID 1) Base Topology (MTID 0) Area BACKBONE(0) Intra-area Route List * 10.58.16.3/32, Intra, cost 0, area 0, Connected via 10.58.16.3, Vlan2 First Hop Forwarding Gateway Tree 10.58.16.3 on Vlan2, count 1 TEST_CoreAB(config)#do sh ip ospf 1 int vlan 2 Vlan2 is up, line protocol is up Internet Address 10.58.16.3/29, Area 0, Attached via Interface Enable Process ID 1, Router ID 192.168.11.246, Network Type BROADCAST, Cost: 1 Topology-MTID Cost Disabled Shutdown Topology Name 0 1 no no Base Enabled by interface config, including secondary ip addresses Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 192.168.11.246, Interface address 10.58.16.3 No backup designated router on this network Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:02 Supports Link-local Signaling (LLS) Cisco NSF helper support enabled IETF NSF helper support enabled Index 1/1/1, flood queue length 0 Next 0x0(0)/0x0(0)/0x0(0) Last flood scan length is 0, maximum is 0 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 0, Adjacent neighbor count is 0 Suppress hello for 0 neighbor(s) I don't know why inactive area 0 on CoreAB.
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1. Yes, that would be the way I would do it. Insert the Nexus as layer 2 and then transition it to the L3 core. I've done just that multiple times with great success.
2. If I understand you correctly I'd have the two Nexus be the DR and BDR. When doing vPC it's best if the switches mirror each other and not have one doing L3 and the other L2. It makes routing easier and offers better overall performance.
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