Tuesday, October 11, 2011
OSPF Loopback Advertisements With Proper Mask - The Tricky Part
There is always a talk going on about among CCNP/CCIP/CCIE candidates that why a loopback interface is always treated as Stub Host into OSPF and Advertised as /32 route even the actual mask for the interface was configured differently.
Actually It's based on RFC standard 2328 for OSPF ver2. Here are ref details :
RFC - 2328 http://www.ietf.org/rfc/rfc2328.txt
Protocol - OSPF Ver 2
Section - 9.1
Page - 66
Tag - Interface States > Loopback
Now interestingly Cisco Documentation provides only a one work-around to this by putting command - ip ospf network point-to-point under the loopback interface itself.
But are there any other ways ? ....
What if our Evil CCIE Lab ask to advertise Loopback interfaces with correct mask and we are not allowed use the command mentioned above :-)
Actually there are three ways to do it, lets explore them one by one.