how to replace spanning tree or MLAG with ECMP?
if whole infrastructure not use spanning tree and MLAG and change to use ECMP,
which switches support?
i see uneqaul cost multiple path support in EIGRP.
isn't ECMP an independent configuration or protocol?
how to configure this?
what is diagram of ECMP design look like
i feel per packet seems having redundancy than per destination, is it?
if use per packet, will it increase packet loss?
if so, it sounds influence UDP only.
which design diagram is the best practice for high availability in ECMP?
Can I assume that when you mention MLAG that you are talking about multi chassis link aggregation group? If so then the answer to your main question is that both spanning tree and MLAG are layer two solutions while ECMP is a layer 3 solution. So replacing spanning tree or MLAG involves redesigning network connectivity to use layer 3 links to connect switches and routers instead of using layer 2 links (access ports, trunk ports, layer 2 Etherchannel, ec). To do this you would need switches that are layer 3 capable.
ECMP is not an independent configuration or protocol. ECMP is an approach to allow forwarding packets over multiple paths toward a destination and is used by multiple routing protocols. ECMP is the default for most dynamic routing protocols and works also with static routes. EIGRP supports ECMP but also is capable of using unequal cost multi path.
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To add to Rick's post, in answer to your question about using per packet load sharing with ECMP (or unequal too), the general answer is don't use it. It often causes packets of the same flow to be delivered out of order.
For optimal load sharing with L3 multi-path, you need something like Cisco's PfR that can monitor and adjust per path loading.