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10-18-2018 02:33 AM
10-18-2018 02:33 AM
OSPF routing confusion/loop?
Hi all
I have noticed strange behaviour between two switches participating in ospf, little diagram below. A and B are connected via ospf network type p2p
what I can't understand is why switch a a still learns 10.3.0.0 range from router b even though they are all directly connected to it
HP-a dis ip routing table 10.3.0.0 Summary Count : 1 Destination/Mask Proto Pre Cost NextHop Interface 10.3.0.0/16 OSPF 150 1 10.10.10.b Vlan10
when checking for IP RT more specifically for one of the 10.3 addresses:
HP-a dis ip routing-table 10.3.2.0 Summary Count : 3 Destination/Mask Proto Pre Cost NextHop Interface 10.3.0.0/16 OSPF 150 1 10.10.10.b Vlan10 10.3.2.0/24 Direct 0 0 10.3.2.1 Vlan100 10.3.2.0/32 Direct 0 0 10.3.2.1 Vlan100
they way this was discovered was quite coincidental by mistyping IP address while performing tracert, ip used didn't exist on the network and the result was that it would bounce between switch a and b until it hit 30 hops, so it looked something like this
Tracing route to 10.3.20.10 over a maximum of 30 hops 1 <1 ms <1 ms <1 ms 10.x.x.1 2 * * * Request timed out. 3 <1 ms <1 ms <1 ms 10.x.x.x 4 1 ms 1 ms 1 ms 10.10.10.a 5 <1 ms <1 ms <1 ms 10.10.10.b 6 1 ms 1 ms 1 ms 10.10.10.a 7 <1 ms <1 ms <1 ms 10.10.10.b 8 1 ms 1 ms 1 ms 10.10.10.a 9 <1 ms <1 ms <1 ms 10.10.10.b 10 1 ms 1 ms 1 ms 10.10.10.a 11 <1 ms <1 ms <1 ms 10.10.10.b 12 1 ms 1 ms 1 ms 10.10.10.a 13 <1 ms <1 ms <1 ms 10.10.10.b 14 1 ms 1 ms 1 ms 10.10.10.a 15 <1 ms <1 ms <1 ms 10.10.10.b 16 1 ms 2 ms 1 ms 10.10.10.a 17 <1 ms <1 ms <1 ms 10.10.10.b 18 1 ms 1 ms 1 ms 10.10.10.a 19 <1 ms <1 ms <1 ms 10.10.10.b 20 1 ms 1 ms 1 ms 10.10.10.a 21 <1 ms <1 ms <1 ms 10.10.10.b 22 1 ms 1 ms 1 ms 10.10.10.a 23 <1 ms <1 ms <1 ms 10.10.10.b 24 1 ms 1 ms 1 ms 10.10.10.a 25 <1 ms <1 ms <1 ms 10.10.10.b 26 1 ms 1 ms 1 ms 10.10.10.a 27 1 ms <1 ms <1 ms 10.10.10.b 28 1 ms 1 ms 1 ms 10.10.10.a 29 1 ms <1 ms <1 ms 10.10.10.b 30 1 ms 1 ms 1 ms 10.10.10.a
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11-18-2018 10:33 PM
11-18-2018 10:33 PM
Re: OSPF routing confusion/loop?
Hello,
The traceroute output shows a routing loop. Can you please check the route pointers in each device for specific destinations.