Simple link upgrade from 1Gb to 10Gb,

Simple link upgrade from 1Gb to 10Gb,

SiteA Sw1 has a 1Gb link to Core Sw2. We want to upgrade it to a 10Gb link.

Easy enough right? Just copy the configs off ports G0/1 on the SiteA Sw1, and the Core Sw2

Then paste them on to ports TenG0/24 on each Sw.

Unplug the fiber at both Sws, and plug into the new ports.

(Now we did a lot of leg work before the upgrade.

We made sure the fiber was good and would support the TenGig

We installed the new optics)

So when we switched over the fiber and the ports lit up,

We just know we were good-to-go.

Buy when we tested the link by shutting down the port to Core Sw1.

…. Was all we got, no eigrp routes, but I could see Core Sw2 with Show CDP neighbors.

Of course this is not good, and I starting thinking what could be wrong.

A quick thinking colleague,  said “passive-interface” and sure enough because Site1 had

Access Layer ports so it was using default passive interface under the EIGRP config.

Core Sw2 was not because it did not have any Access Layer ports.

No default passive-interface t0/24 on SiteA Sw1 worked like a charm.

!!!! All day long.

Just goes to show you how not thinking about the big picture and a little command,

Can sneak up and bite you.