routing protocol-best path.

[tushar47]

Dear sir,

I want to know, if a Route is advertised by 2 Routing protocols, then which route by which protocol will be preferred.

1) 192.168.3.0/24 is advertised by BGP

192.168.3.0/27 is advertised by OSPF.

If I trace route IP 192.168.3.5, then which IP

will be preferred.

2) 192.168.3.0/24 is advertised by EIGRP.

192.168.3.0/27 is advertised by OSPF.

If I trace route IP 192.168.3.5, then which IP

will be preferred.

Please tell me what are the different issues in Path selection?

Regards,

Ashu

[Georg Pauwen]

Hello Ashu,

in both your examples, the OSPF route will be chosen, because the route with the longest (that is, most specific) prefix match is preferred.

Check the following document, it has a pretty good description of the different criteria in path selection:

Route Selection in Cisco Routers

http://www.cisco.com/warp/public/105/21.html

HTH,

GP

[Richard Burts]

Georg is quite right that the longest prefix is preferred. Administrative Distance only is considered when two prefixes are equal including the same length. Even though both prefixes in this example have the same numeric content (192.168.3.0) they are not equal because they are different lengths.

Another way to look at the effect of this is that in both cases the OSPF route will be preferred for addresses 192.168.3.0 through 192.168.3.31 and the BGP/EIGRP route will be preferred for addresses 192.168.3.32 through 192.168.3.255.

HTH

Rick

[tushar47]

thank you sir.

Regards,

Ashu