Which book to believe on OSPF ID?

The self study guide says the following;
[Alternatively, if the router-id ip-address OSPF router configuration command is used, it will override the use of the address
of a physical or loopback interface as the router ID. Using the router-id command is the preferred procedure for setting
the router ID.]

The exam guide says this;
[Generally, using the router-id command is not recommended because BGP and OSPF normally
pick a router ID the same way. Manually specifying a router ID can result in these IDs differing,
which can be a source of problems with BGP operation]

Both are cisco press books, but obviously now there is a conflict between cisco people

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Comments

scheistermeister

I would use the router-id command... Mainly because if you let the router pick the ID you can have problems later if the router picks the wrong ID.

ccnpninja

Here's the order :
1- Router ID
2- (if there's only one loopback) the loopback's IP address
3- higest IP address of all physical interfaces

dtlokee

The OSPF router ID has no effect on the BGP router ID and vice versa. Why do they need to be the same? It is mostly for convience rather than out of necessity. It may be confusing if the routing protocols have the same neighbor with different router IDs. Now in most cases on most network allowing the routers to select their router ID automatically should not present an issue. There are a few cases where hard coding the router ID is beneficial, like using a virtual link (which you shouldn't use anyhow). My other thought would be if you are using the router ID to set the value to an address that is not assigned to any interface on the router you can't use ping or traceroute to it, that could make management and troubleshooting difficult.

kryolla

does it have anything to do with OSPF-BGP redistribution or sync?

wat08

Are you referring to this study guide...

http://www.ciscopress.com/bookstore/product.asp?isbn=158705146X

...and this exam guide?

http://www.ciscopress.com/bookstore/product.asp?isbn=158720147X

Which one would you recommend as a primary resource? The self-study guide publication date worries me...