I am new with the JUNOS. i configured ospf between two connected routers and by mistake i configured the same ip address on both the interfaces . but the ospf neighbourship stuck at Exstart state. In the other vendors (CISCO, Huawei) this is not the behaviour.
can anyone please explain me dispite of dupticate address how both the routers reached at Extart State?
To answer you question, the routers use the interface IP's to establish OSPF and at this stage it is struck because both DR and BDR are having the same IP address which is a misconfiguration. Ideally this can be identified using the outputs of monitor traffic where you will observe that the IN and OUT packet have the same IP address.
This conflict is not letting OSPF transition to next state and would not allow the full adjacency to complete.
r@R1_re> show ospf neighbor Address Interface State ID Pri Dead 10.10.10.2 ge-0/0/0.0 ExStart 126.96.36.199 128 33 >> Yes this is expected.
r@R1_re> show ospf neighbor detail
Address Interface State ID Pri Dead
10.10.10.2 ge-0/0/0.0 ExStart 188.8.131.52 128 36
Area 0.0.0.0, opt 0x12, DR 10.10.10.2, BDR 10.10.10.2 >> Duplicate IP
master, seq 0x805fae4e, rexmit DBD in 0 sec
r@R1_re> monitor traffic interface ge-0/0/0
verbose output suppressed, use <detail> or <extensive> for full protocol decode
Address resolution is ON. Use <no-resolve> to avoid any reverse lookup delay.
Address resolution timeout is 4s.
Listening on ge-0/0/0, capture size 96 bytes
Reverse lookup for 10.10.10.2 failed (check DNS reachability).
Other reverse lookup failures will not be reported.
Use <no-resolve> to avoid reverse lookups on IP addresses.
05:15:42.200997 Out IP truncated-ip - 20 bytes missing! 10.10.10.2 > ospf-all.mcast.net: OSPFv2, Hello, length 60
05:15:45.922755 In IP 10.10.10.2 > ospf-all.mcast.net: OSPFv2, Hello, length 60
05:15:51.631514 Out IP truncated-ip - 20 bytes missing! 10.10.10.2 > ospf-all.mcast.net: OSPFv2, Hello, length 60
05:15:55.573192 In IP 10.10.10.2 > ospf-all.mcast.net: OSPFv2, Hello, length 60
Please mark "Accept as solution" if this answers your query. Kudos are appreciated too!
Please pay attention to "SHOULD" language used in RFC, not "MUST".
As to why DBD did not go through - OSPF Database Exchange is unicast, so in order to send unicast OSPF DB Exch packets, the router needs to find out first what peer MAC is. The router tries to resolve peer IP to a MAC, and of course finds out that IP is also own IP and own MAC! Hence, unicast OSPF DB Exchange is not attempted.
Thanks for your responce, i configured ospf between two routers with duplicate address but this time with P2P network type. in this case i think ospf detected duplicate addresses at its initial stages (down, init ) because when i checked with "show ospf neighbor" command it was showing nothing. In the P2P network type all the ospf messages are sent on multicast address(184.108.40.206) then how its being detected ?