OSFP & wildcard mask
Hey Team,
I'm confused on the different "formats" to config ospf interfaces. Especially, with the wildcard mask portion like when 0.0.0.0 or 255.255.255.255 is used? Is one better then the other??
I'm confused on the different "formats" to config ospf interfaces. Especially, with the wildcard mask portion like when 0.0.0.0 or 255.255.255.255 is used? Is one better then the other??
Comments
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networker050184
Mod Posts: 11,962 Mod
One isn't "better" than the other. They are used for two different things. You should revisit your binary basics.An expert is a man who has made all the mistakes which can be made. -
kryolla
Member Posts: 785
0.0.0.0 is the most specific if you only want that one interface partcipating in OSPF and 255.255.255.255 is everything that is up will participate in OSPF.
network 172.16.15.1 0.0.0.0 area 0
network 0.0.0.0 255.255.255.255 area 0Studying for CCIE and drinking Home Brew -
phantasm
Member Posts: 995
As for wildcard bits. If you had a 192.168.2.0 /26 then your mask would be 0.0.63.255 if you only wanted to allow that range of subnets.
I believe that's correct. Someone smack me if it isn't. It's been a long morning at the office. lol."No man ever steps in the same river twice, for it's not the same river and he's not the same man." -Heraclitus -
kryolla
Member Posts: 785
phantasm wrote:As for wildcard bits. If you had a 192.168.2.0 /26 then your mask would be 0.0.63.255 if you only wanted to allow that range of subnets.
I believe that's correct. Someone smack me if it isn't. It's been a long morning at the office. lol.
/26 is 255.255.255.192 and the inverse mask is 255 minus 192 so it is 0.0.0.63
you might be thinking about /18Studying for CCIE and drinking Home Brew -
phantasm
Member Posts: 995
kryolla wrote:phantasm wrote:As for wildcard bits. If you had a 192.168.2.0 /26 then your mask would be 0.0.63.255 if you only wanted to allow that range of subnets.
I believe that's correct. Someone smack me if it isn't. It's been a long morning at the office. lol.
/26 is 255.255.255.192 and the inverse mask is 255 minus 192 so it is 0.0.0.0.63
you might be thinking about /18
it should've been 0.0.0.63. lol. Long morning. Either way if my brainw ould cooperate then your wildcard mask is 1 less of the block size. So with a /26 your block size is 64, your mask bit would be 63."No man ever steps in the same river twice, for it's not the same river and he's not the same man." -Heraclitus -
cdad2000
Member Posts: 323
Great!! So one is more specific on which networks to advertise. 0.0.0.0 is for that one specific interface and 255.255.255.255 advertise everything.
P.S> My subnetting fine, I could VLSM an IPv6 watch ffff:U:BRICK::050184/16
Thanks everybody..else -
networker050184
Mod Posts: 11,962 Mod
I wasn't trying to be an a$$, my apologies if you took it that way. All I was trying to convey was that it is simple binary to see what the wild card mask matches.
Also, the wildcard mask in the OSPF network statement has nothing to do with your subnet mask. All the network statement does is tell the OSPF process which interface to run on.An expert is a man who has made all the mistakes which can be made. -
tech-airman
Member Posts: 953
cdad2000 wrote:Hey Team,
I'm confused on the different "formats" to config ospf interfaces. Especially, with the wildcard mask portion like when 0.0.0.0 or 255.255.255.255 is used? Is one better then the other??
cdad2000,
Do you understand the difference between a multi-access OSPF segment and a non-broadcast multi-access OSPF segment?
Link:
