The "poison squashed" indicates that the remote router is doing split-horizon with poisoned reverse, which is by default turned on in EIGRP.
The message means that the router is getting a routing update from its neighbor with an unreachable(a poison) metric, about which this MSFC doesnt anything about, and thus we will discard it(squash) without processing it.
3. r1 will build eigrp neighbor with 7500,and send update to 7500.
4. 7500 receive update and begin DUAL.because r1 is not successor of 7500 except 10.76.0.0(suppose this),so DUAL is local-compution,and 7500 will not send update to other except 10.76.0.0.
5. 7500 will reset sh ip route timeclock,so when I show ip route,all route 's uptime will change frequently because my wan is not stablity.And I show ip eigrp nei,I found there is one neighbor's uptime is same as sh ip route uptime.
So I think this is the reason.and I found this on routing tcp/ip vol 1 p 207:
A router will reassess its list of feasible successors for a route, as described in the last section, any time an
input event occurs. An input event can be:
A change in the cost of a directly connected link
A change in the state (up or down) of a directly connected link
The reception of an update packet---->this is the reason?
The reception of a query packet
The reception of a reply packet
English is not my native language,so I can't express exactly what I think.
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