| Author |
Regarding Loopback
|
|
| Mad21maxx 2003-05-03, 3:27 pm |
| In configuring OSPF and I have a Loopback interface, can that interface have a regular subnet mask or does it need to have a 32-bit subnet mask(255.255.255.255).
And would it be advantageous to include the loopback interface in the network commands.
thaks for your help | |
| SureshHomepage 2003-05-03, 5:06 pm |
| The purpose of using the loopback interfaces is to have a firm router id.
This router-id is a component of every ospf exchange including Hello packets and LSA advertisements. Also it plays an important role in the DR election. Now it becomes highly desirable to have a router id that does NOT change. Loopbacks are the best choice here.
OSPF automatically takes the numerically highest IP address of any loopbacks configured on a router as thier choice for a router-id if you don't specify one.
Its subnet mask can be anything including the 32 bit mask as you mentioned here. Absolutely no hassles at all.
If you have used a non-32 bit mask but for some reasons you expect a 32-bit mask to appear on the routing table, just use the command "ip ospf network point-to-point" on the LOOPBACKs. This command would change it and make it appear as a 32-bit host id immaterial of the mask you used.
Hope this would help! | |
| Mad21maxx 2003-05-03, 5:39 pm |
| Thanks for the explanation.
It all seems alot clearer now. | |
|
| You can also use the command ..
area x range <your loopback network> <mask>
This will advertise both the /32 and /24 in your OSPF unless u block that...
for sure "ip ospf net point-to-point" is more convenient.. but for "area x..." just worth mentioning..  |
|
|
|