Arista EOS — Deployment

Stage, diff, commit and roll back fabric changes for Arista EOS data center fabrics (VXLAN/EVPN). Part of the multi-vendor Data Center automation guide.

Repository

Arista

EOS

eAPI

VXLAN / EVPN

Render per-vendor config from the intent model

Stage as a candidate on Arista, then diff

Commit only the expected diff — roll back on failure

Setup, key commands & run examples

deploy.sh

Stage / diff / commit

The Arista EOS change workflow. EOS named configuration sessions give you a true candidate config: stage changes in a session, review show session-config diffs, then commit atomically or abort. eAPI (JSON-RPC) is ideal for structured collection.

deploy.sh

bash

# 1. stage:   configure session <name> (named config session)
# 2. diff:    show session-config diffs
# 3. commit:  commit (within the session)
# 4. revert:  abort / configure session <name> abort

deploy.py

Guarded commit

Render config from intent, stage it on Arista, preview the diff and only commit when it matches what you expect.

deploy.py

python

dev.load_merge_candidate(config=rendered)   # configure session <name> (named config session)
diff = dev.compare_config()                 # show session-config diffs
print(diff)
if diff and "vlan 120" in diff:
    dev.commit_config()                     # commit (within the session)
else:
    dev.discard_config()

Best practices

Diff before every commit
Always review show session-config diffs (or gate it in CI) so no Arista change is applied blind.
Deploy leaf-pairs, not rows
Roll one MLAG/ESI pair at a time and verify before moving on, so redundancy survives a bad change.
Confirmed commits
Arista has no confirmed-commit — keep a rollback (abort / configure session <name> abort) one command away and watch the session.
Post-change verification
Re-read EVPN/VTEP state after each commit and abort the rollout if anything regressed.

Hands-on exercises

Guided practice tasks — copy the starter snippet, run it against a lab device, and extend it to meet the goal.

Exercise 1

Guarded VLAN rollout

Goal: Add an L2VNI to one Arista leaf pair: stage, print the diff, commit only if it contains the expected VLAN id.

exercise_1

python

rendered = render_l2vni(vlan=120, vni=10120)
# TODO: stage -> diff -> commit only if "120" in diff, else discard

Exercise 2

Rollback drill

Goal: Apply a bad change, detect the EVPN peer drop, and roll back with: abort / configure session <name> abort

exercise_2

bash

# apply change, then on failure:
abort / configure session <name> abort

Curated videos & guides

Checklist — pitfalls, gotchas & verification

Common pitfalls

•Committing without reviewing the diff first.
•Deploying both leaves of an MLAG/ESI pair at once and dropping the redundant path.
•Assuming Arista commit semantics match other vendors — they differ.

Gotchas to watch

•compare_config() returns an empty string (not None) when there is no change — test truthiness.
•Losing your management session mid-commit can lock you out without confirmed-commit.

Verify it works

•After deploy, re-read EVPN neighbors and confirm every peer returned to up.
•Diff running-config against intent post-change to prove zero unexpected drift.