RSTP vs EIGRP

Matt Hoppes · ‎09-25-2012

This question really has two parts to it, and I realize RSTP and EIGRP are two completely different animals.

PART 1:

What can I expect the average convergance time to be on an RSTP network (issuing the command:

spanning-tree mode rapid-pvst on my switches) of something like 12-15 switches?

With STP active when one side of the link goes down things pickup again pretty quickly on the back-up side, but when the network comes back together the entire network takes a crash as a loop forms for about 10-15 seconds while STP gets itself in order.
(I realize the switch will block a port when its plugged in, but for this example assume the port never went down, but rather it was a long haul ethernet provider's circuit that went down -- so the circuit was down, but the Ethernet was up).

What kind of convergeance times can I expect with RSTP when the link/ring comes back together?

PART 2:In a network of 12-15 nodes, is running EIGRP over RSTP over-kill, or a good measure if the goal is to provide redundant routes?  Basically I need less than a second of down time between switching directions on the ring.

I think I already know the answer to this, but want to hear from the community.

cadet alain · ‎09-25-2012

Hi,

with rapid spanning-tree reconvergence should take a few seconds

EIGRP is L3 protocol so not run on L2 links but if you use routed ports and get rid of STP then EIGRP reconvergence

is very fast and can go down to msecs with BFD but the design is very important especially for alleviating SIA routes.

Regards.

Alain

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Matt Hoppes · ‎09-25-2012

Thanks Cadet Alain,

So the question really is (and I plan to play around with this a bit tomorrow), during the RST reconvergence does the network become unavailable/unusable until RST kills the loop port?

Jon Marshall · ‎09-25-2012

Matt

Yes you will lose packets for this vlans that RSTP is reconverging for. Bear in mind with RSTP it is done on a per vlan basis so if a link goes down that only carries 2 of your vlans for example on these vlans will be affected.

Jon