[j-nsp] Loopback IP address in BGP Peering

[C T]

Just to add a comment.
Some people confuse it, including me sometimes... :-)
 
Even a router or a system with Classfull (without CIDR) the address z.y.x.0 or z.y.x.255 can be considered valid host addresses.
 
For instance, if you have a class B 128.3.0.0 (CIDR equivalent of 128.3.0.0/16)
The addresses:
128.3.10.0 is a valid host address
128.3.10.255 is a valid host address
 
But using class C, the .255 and .0 are invalid host addresses.
 
Good reference at: http://tools.ietf.org/html/rfc4632
 
Cheers,
Claus T
 
>All major vendors support 0 and 255 as loopback in the last octet. o if >you are using J or C for instance, your safe. If you use an obscure >small vendor, the choice to use 0 and 255 can come back and bite >you in the ***.
>Cheers
>Patrik
>Mark Tinka wrote:
> On Saturday 28 February 2009 06:31:15 pm Cougar wrote:
> 
>> What kind of exception is this? In CIDR world you can use any address 
>> you like except first and last _LAN_ addresses when netmask is /30 or 
>> less. With /31 and /32 can use any address and so far I haven't seen 
>> any problems using x.x.x.0 or x.x.x.255 in Junipers.
> 
> That may very well be - but my suggestion is just because it can be 
> done, doesn't mean it's a great idea "all around".
> These are the types of practices that come back and bite you due to 
> varying levels of support for implementing .0 and
> .255 across various pieces of software. I'm not presuming the OP has 
> only Junipers to deal with in their network.
> 
> Given the number of addresses one may potentially save in, say, a /24 
> sliced only for Loopbacks vs. not getting stressed by why this may 
> break some things in the network; I'd much rather sacrifice those two 
> addresses, thank-you- very-much.
> 
> Keep it simple, keep it stupid, keep it unambiguous. The physics don't 
> change, just how you apply them.
> 
> Then again, to each his own...
> 
> You probably want to spend some time wading through:
> 
> http://tinyurl.com/dzw4cj
> http://tinyurl.com/av8rwm
> http://tinyurl.com/chwjms
> 
> Mark.
> 
> 
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