Black Jack wrote: > > Hmm...that suggests that a VLSM-aware redirect would be useful. > Send the mask along with the network address in other words. > Does such a thing exist, or has it ever been proposed?
I don't think such a thing has been proposed. Also, it may not be practical. The router sending the Redirect might not know about the subnet masking being used elsewhere on the network either? I guess it would depend on the routing protocol. There are always tradeoffs. It's probably a good thing that the host receiving the "Redirect for Network" places a host-specific route into its routing table, for all the reasons already mentioned (classless addressing, VLSM, discontiguous subnets.) But what's the tradeoff? ? give it some thought.... don't want to give it away right away.... think..... analyze.... ideas? It might be obvious, but the tradeoff is that the host could end up with a bunch of host-specific routes in its table. It sends to 10.0.0.1, gets a redirect, places the host-speficic route in its table. It sends to 10.0.0.2, gets a redirect, places the host-specific route in its table. Etc. So, what's so bad about that? Well, it's extra processing and it uses a little extra memory (not a big deal these days, granted!) But as the list gets longer, lookups and placing new entries will take longer and longer. So some delay might occur. Just some more thoughts to get y'all thinking! :-) Priscilla > > > > Answer: The host can't know about subnet masks being used > > elsewhere. Also, with classless addressing, it can't assume a > > Class A mask for network 10.0.0.0. > > > > The host can't know for sure that ALL of 10.0.0.0/8 is > > reachable by the router that claims that it is. With > > variable-length subnet masking, classless addressing, > > discontiguous subnets and all the other things people do to > > their network designs, the safest thing for the host to do is > > to place a host-specific route into its table. > > > > Just thought I'd turn this into a more advanced "lesson." :-) > > > > _______________________________ > > > > Priscilla Oppenheimer > > www.troubleshootingnetworks.com > > www.priscilla.com > > > > > > > > > > > > > > > > Thanks in advance. > > > > > > -DJ > > > > > > > > > > > > > > > --------------------------------- > > > With Yahoo! Mail you can get a bigger mailbox -- choose a > size > > > that fits your needs > > > > > > > > > > > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=61063&t=61004 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
