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OSPF Router ID?

In OSPF routing why we configure this command on each router like I have seen a training the instructor was configuring router-id 1.1.1.1 on 1st router and 2.2.2.2 on 2nd and so on... on each router? Is it replacement of loopback interface or priority command to explicitly define DR? Pls explain.

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Accepted Solutions

Re: OSPF Router ID?

router B will become DR if both the router have same or equal priority...

but if both router have different priority the router with the highest priority will become DR...

regards

Devang

5 REPLIES

Re: OSPF Router ID?

yes it is,

here you are force the router to use the router ID which is configured with the "router-id a.b.c.d"

you can have same configuration in BGP also...

regards

Devang

New Member

Re: OSPF Router ID?

Thanks for reply Devang.

Now I have two questions.

1- I saw a CCIE trainer, he assigned the router-id 1.1.1.1 and immediately after this he is also configuring priority 255 on the same router. Why it is like this?

2- This router-id should always be some kind of IP address. I mean same rule the router who has the highest IP address configured as router-id will be the DR.

Pls explain.

Re: OSPF Router ID?

actually priority is used to infulance the DR and BDR selection process in the OSPF area...

router with the higer priority will become DR, you can assign the priority between 0 to 255, if you configure the priority vlaue 0 then that router can not be DR or BDR or you can say its noteligibel for DR and BDR election... if the priority on the all router is same then the DR router is the router with the highest Router ID...

regards

Devang

New Member

Re: OSPF Router ID?

Thanks.

Final question:

If one router A is configured with router-id 1.1.1.1 command and router B configured with router-id 2.2.2.2 command, then who will be the DR?

Re: OSPF Router ID?

router B will become DR if both the router have same or equal priority...

but if both router have different priority the router with the highest priority will become DR...

regards

Devang

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