From: gladston@br.ibm.com
Date: Sun Oct 31 2004 - 02:53:41 GMT-3
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quoted
Regarding the routers used in the lab, even though these routers support both
trunking protocols, ISL and 802.1q, they don't support DTP (Dynamic Trunking
Protocol), correct?
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Correct. I remember a recommendation saying to configure the trunk and etherchannel with no dynamic protocols, between router and switch.
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quoted
Also, from what I can tell, routers don't suppport either of the EtherChannel
aggregation protocols, LACP or PagP, true?
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True.
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quoted
Now, assuming the above statements are true, I'm wondering how the 3550 side
of the links connected to a router should be configured. If the router
doesn't support any of these negotiation protocols, I assume that on the 3550
side, I should make sure no negotiation is done. Is this assumption correct?
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Yes. The better would be configure the trunk with "switchport mode trunk" and nonegotiate to disable DTP. And configure etherchannel "on" (that is, disable PagP and LACP).
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quoted
Also, what happens if I forget or misconfigure the 3550 side such that it
tries to negotiate with the router?
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If there was a bridge configured on the two interfaces of the router, (and the channel was layer 2), a loop could occur, as when configuring wrongly etherchannel between two 3550.
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