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Home > Archive > CCNP > February 2002 > interface loopback with ospf
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interface loopback with ospf
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| zaza230 2002-02-10, 3:38 am |
| I read the section many time but I don't really understand the way it's use ?
when to use it ? should it be advertised with the network area ? . any input will be greatly appreciated | |
| MadChef 2002-02-10, 5:41 am |
| quote:
Originally posted by zaza230
I read the section many time but I don't really understand the way it's use ?
when to use it ? should it be advertised with the network area ? . any input will be greatly appreciated
You can advertise it if you want the loopback to be reachable throughout your network, but there's nothing that says you HAVE to. As far as OSPF is concerned, it only uses the loopback to set the Router ID and that doesn't require reachability. It's all the other services that can use the loopback that require reachability. One can set the loopback to be the source and destination of services like ntp, snmp, dlsw, etc. Many places resolve the hostname to the address of the loopback. The loopback is used because if the router is at all reachable, then you can get to the loopback. If you resolved to the ethernet address then there's always the possibility that someone unplugs the interface and it goes down and is unreachable by that address now, even though the router is up and perfectly operational. In these cases you'd definately want to include the loopback in your network area statements.
You should also be aware that you can use 32 bit masks on your loopback interfaces so you don't waste address space. You can have 10 different routers with otherwise differnet address space with loopbacks address 192.168.255.1-10/32, if that makes sense. I bring this up because it really confused me when I first saw this and it's extremely common for a network admin to use one section of address space (192.168.255.x, for example) to number all their loopbacks.
MadChef | |
| zaza230 2002-02-11, 7:38 am |
| thank you very much for your brigthful explanation | |
| MadChef 2002-02-11, 6:20 pm |
| quote:
Originally posted by zaza230
brigthful
Next time try "enlightening", as brightful isn't really a word. 
Personally, I'm always amazed at non-native English speakers in this industry (and I lump people from the UK in there too, sometimes.  ) If things were changed around and all Cisco configuration and documentation was in French, I'd be the guy setting my coffee cup in my CDROM tray because I'd be so computer illiterate. You guys amaze me, so take my grammer hints as attempts to be helpful, not critical.
MadChef | |
| peterd 2002-02-12, 2:54 am |
| Hi MadChef,
we give you a language and look at the mess you make of it...
:-)
Regards
Peter | |
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Englesh is the bestest lingo in the world. I've been learning to speak well English ever since I was a children.
Tee-hee
Hippo (now studying weller english and grammer)
Fair point though. I can speak French to near converstaional level, a little bit of Spanish and I can order a beer in Dutch. But it never fails to amaze me, that our European colleagues can not only speak, but master several European languages. It puts us English to shame really. | |
| peterd 2002-02-12, 7:22 am |
| Hi,
when I was at school we didn't have any foreign languages unless you went to a grammar school, and this was back in the days before the EU when each country (especially France & Germany) thought that their language should be the 'international' language.
I worked in Amsterdam for 14 months a couple of years ago, learnt some Dutch, but it was almost impossible as the other guys immediately switched to English when speaking with me, I never had a chance to practice anything that I'd learnt.
So it's not entirely our fault that we don't pick up other languages.
Anyway, everyone speaks English so we don't need to learn their languages.
Regards
Peter | |
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Peter; I agree with you about the Dutch. I was there for 12 months - AT&T Unisource at Hoofddorp (June 97 to June 98).
I did learn some Dutch, but when I tried it on the 'cloggies' they pretended not to understand me and went into Engels.
BTW, I was one of those grammar school kids what learnt foreign lingo.
Hippo | |
| peterd 2002-02-12, 10:01 am |
| Hi Hippo,
hmm, I was once invited out to dinner by one of our clients and ended up sitting opposite the boss-man of AT&T Europe...
though I can't remeber his name now...
maybe because I was sitting between two stunningly gorgeous Dutch girls...
Regards
Peter |
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