Extreme switch has different algorithm to select router id from other vendor ( for ex. cisco ). Because of this difference, customer used to have wrong expectation for EXOS based switch regrading OSPF router id. I wrote this article to shows what is the method to select router id on EXOS, and what is recommendation on EXOS.
Cause of user's Wrong expectation
The selection method is not defined in RFC and each vendor has different method.
Per RFC 2328 (OSPFv2):
"Router ID
A 32-bit number assigned to each router running the OSPF protocol. This number uniquely identifies the router within an Autonomous System." A method of selecting isn't stated
In case of cisco, if router id not configured manually, then router choose highest ip address from loopback interface, and choose highest IP addresses from physical interface if there is no available loopback ip address, but extreme switch choose highest ip address among all ip address which is configured on switch unless router id has not been configured manually.
Best Practices
Manually configure a Router ID.
It is recommended that you manually set the router ID of the switches participating in OSPF instead of having the switch automatically choose its router ID based on the highest interface IP address.
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