North American Network Operators Group

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Re: IGPs and services?

  • From: Stephen Sprunk
  • Date: Fri May 19 14:13:20 2000

Sez "Brandon Ross" <[email protected]>
> What platform adds static routes in response to PMTU discovery?  I've
> never seen that before.  What purpose does it serve to add statics?
> kind of caching of MTU per destination?

This is actually very common in "off-brand" (ie. anything besides Linux,
*BSD, and Solaris) IP stacks.  The current shipping versions of many
OSes do some very odd things: cache a static route upon performing
PMTUD, cache static routes to one of multiple default gateways, refuse
to honor gratuitous ARPs, refuse to time out ARP entries, cache ARP
entries with mcast MACs, cache ICMP redirects classfully, etc.

What's worse is these "caches" tend to be permanent, usually not even
allowing manual overrides (other than a reboot).


     |          |         Stephen Sprunk, K5SSS, CCIE #3723
    :|:        :|:        Network Consulting Engineer, NSA
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