[c-nsp] Best practice - Core vs Access Router

Saku Ytti saku at ytti.fi
Tue Feb 9 12:27:55 EST 2010

On (2010-02-09 17:56 +0100), Andy B. wrote:

> Excuse me for being ignorant, but what are glean punts? Should I dig
> out my routing for dummies book :-/

No ignorance, sorry for being so terse, just wanted to avoid rambling
on too much.

Glean are packets which need to be punted because forwarding information is
incomplete, in this case because it is locally connected destination
without valid hardware (MAC) forwarding address.
To resolve IP address, you'll ARP it, and this is software function, to be
able to trigger ARP you'll need to punt the packet to software.

As you have huge LAN, it is likely also very empty, so you might get sudden
burst of packets spread around the LAN, which would suddenly punt many
packets to software.

If BGP/OSPF is running over same physical interface, incoming BGP/OSPF
keepalive might be dropped, since there is no room to punt it (actually SPD
should have some extra room for them) causing BGP keepalive to be dropped.

When OSPF/BGP goes down, is it always one side tearing it down due due to
hold-time expiring? If it is always the same and always the router under
discussion this would support my hypothesis.


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